Christopher K. Zarins

Abstract

Endovascular aneurysm repair (Greenhalgh in N Engl J Med 362(20):1863-1871, 2010) techniques have revolutionized the treatment of thoracic and abdominal aortic aneurysm disease, greatly reducing the perioperative mortality and morbidity associated with open surgical repair techniques. However, EVAR is not free of important complications such as late device migration, endoleak formation and fracture of device components that may result in adverse events such as aneurysm enlargement, need for long-term imaging surveillance and secondary interventions or even death. These complications result from the device inability to withstand the hemodynamics of blood flow and to keep its originally intended post-operative position over time. Understanding the in vivo biomechanical working environment experienced by endografts is a critical factor in improving their long-term performance. To date, no study has investigated the mechanics of contact between device and aorta in a three-dimensional setting. In this work, we developed a comprehensive Computational Solid Mechanics and Computational Fluid Dynamics framework to investigate the mechanics of endograft positional stability. The main building blocks of this framework are: (1) Three-dimensional non-planar aortic and stent-graft geometrical models, (2) Realistic multi-material constitutive laws for aorta, stent, and graft, (3) Physiological values for blood flow and pressure, and (4) Frictional model to describe the contact between the endograft and the aorta. We introduce a new metric for numerical quantification of the positional stability of the endograft. Lastly, in the results section, we test the framework by investigating the impact of several factors that are clinically known to affect endograft stability.

View details for DOI 10.1007/s10237-012-0450-3

View details for Web of Science ID 000324378900002

View details for PubMedID 23143353

Abstract

Treatment of abdominal aortic aneurysms with high-risk anatomy (neck length <10-15 mm, neck angle >60°) using commercially available devices has become increasingly common with expanding institutional experience. We examined whether placement of approved devices in short angled necks provides acceptable durability at early and intermediate time points.A total of 218 patients (197 men, 21 women) at a single academic center underwent endovascular aneurysm repair (EVAR) with a commercially available device between January 2004 and December 2007. Available medical records, pre- and postoperative imaging, and clinical follow-up were retrospectively reviewed. Patients were divided into those with suitable anatomy (instructions for use, IFU) for EVAR and those with high-risk anatomic aneurysm characteristics (non-IFU).IFU (n = 143) patients underwent repair with Excluder (40%), AneuRx (34%), and Zenith (26%) devices, whereas non-IFU (n = 75) were preferentially treated with Zenith (57%) over Excluder (25%) and AneuRx (17%). Demographics and medical comorbidities between the groups were similar. Operative mortality was 1.4% (2.1% IFU, 0% non-IFU) with mean follow-up of 35 months (range 12-72). Non-IFU patients tended to have larger sac diameters (46.7% ≥60 mm) with shorter (30.7% ≤10 mm), conical (49.3%), and more angled (68% >60°) necks (all p < .05 compared with IFU patients). Operative characteristics revealed that the non-IFU patients were more likely to be treated utilizing suprarenal fixation devices, to require placement of proximal cuffs (13.3% vs. 2.1%, p = .003), and needed increased fluoroscopy time (31 vs. 25 minutes, p = .02). Contrast dose was similar between groups (IFU = 118 mL, non-IFU = 119 mL, p = .95). There were no early or late surgical conversions. Rates of migration, endoleak, need for reintervention, sac regression, and freedom from aneurysm-related death were similar between the groups (p > .05).EVAR may be performed safely in high-risk patients with unfavorable neck anatomy using particular commercially available endografts. In our experience, the preferential use of active suprarenal fixation and aggressive use of proximal cuffs is associated with optimal results in these settings. Mid-term outcomes are comparable with those achieved in patients with suitable anatomy using a similar range of EVAR devices. Careful and mandatory long-term follow-up will be necessary to confirm the benefit of treating these high-risk anatomic patients.

View details for DOI 10.1016/j.ejvs.2013.03.027

View details for Web of Science ID 000321883200013

View details for PubMedID 23628325

Abstract

Stem cell therapies hold great promise for repairing tissues damaged due to disease or injury. However, a major obstacle facing this field is the difficulty in identifying cells of a desired phenotype from the heterogeneous population that arises during stem cell differentiation. Conventional fluorescence flow cytometry and magnetic cell purification require exogenous labeling of cell surface markers which can interfere with the performance of the cells of interest. Here, we describe a non-genetic, label-free cell cytometry method based on electrophysiological response to stimulus. As many of the cell types relevant for regenerative medicine are electrically-excitable (e.g. cardiomyocytes, neurons, smooth muscle cells), this technology is well-suited for identifying cells from heterogeneous stem cell progeny without the risk and expense associated with molecular labeling or genetic modification. Our label-free cell cytometer is capable of distinguishing clusters of undifferentiated human induced pluripotent stem cells (iPSC) from iPSC-derived cardiomyocyte (iPSC-CM) clusters. The system utilizes a microfluidic device with integrated electrodes for both electrical stimulation and recording of extracellular field potential (FP) signals from suspended cells in flow. The unique electrode configuration provides excellent rejection of field stimulus artifact while enabling sensitive detection of FPs with a noise floor of 2 ?V(rms). Cells are self-aligned to the recording electrodes via hydrodynamic flow focusing. Based on automated analysis of these extracellular signals, the system distinguishes cardiomyocytes from non-cardiomyocytes. This is an entirely new approach to cell cytometry, in which a cell's functionality is assessed rather than its expression profile or physical characteristics.

View details for DOI 10.1039/c2lc40905d

View details for Web of Science ID 000312219100006

View details for PubMedID 23207961

Abstract

The purpose of the present study was to investigate whether tanshinone IIA (Tan IIA), one of the major lipophilic components of Salvia miltiorrhiza Bunge, could inhibit the development of elastase-induced experimental abdominal aortic aneurysms (AAAs).Male Sprague-Dawley rats (n = 12/group) were randomly distributed into three groups: Tan IIA, control, and sham. The rats from the Tan IIA and control groups underwent intra-aortic elastase perfusion to induce AAAs, and the rats in the sham group were perfused with saline. Only the Tan IIA group received Tan IIA (2 mg/rat/d). The maximum luminal diameter of the abdominal aorta was measured before and 5, 12, 18, and 24 d after perfusion. The systolic blood pressure was measured twice using the tail cuff technique before administration and death. Aortic tissue samples were harvested at 24 d and evaluated using reverse transcriptase-polymerase chain reaction, Western blot, immunohistochemistry, and Miller's elastin-Van Gieson staining.The rats in the control group had significantly increased aortic sizes compared with the sham group after 24 days (P < 0.05), and the Tan IIA group had a significant reduction in aortic size (Tan IIA versus control, P < 0.05) without affecting blood pressure (P > 0.05). The overexpression of matrix metalloproteinase-2, metalloproteinase-9, monocyte chemotactic protein-1, and inducible nitric oxide synthase and the depletion of elastic fibers and vascular smooth muscle cells induced by elastase perfusion were significantly decreased by Tan IIA treatment (P < 0.05).Tan IIA inhibited the development of elastase-induced experimental AAAs by suppressing proteolysis, inflammation, and oxidative stress and preserving vascular smooth muscle cells. It could be a new pharmacologic therapy for AAAs.

View details for DOI 10.1016/j.jss.2012.04.068

View details for Web of Science ID 000311090700073

View details for PubMedID 22640888

View details for Web of Science ID 000312114600011

View details for PubMedID 23210874

Abstract

Vascular ultrasound can provide quick and reliable diagnosis of arterial bleeding but it requires trained and experienced personnel. Development of automated sonographic bleed detection methods would potentially be valuable for trauma management in the field. We propose a detection method that (1) measures blood flow in a trauma victim, (2) determines the victim's expected normal limb arterial flow using a power law biofluid model where flow is proportional to the vessel diameter taken to a power of k and (3) quantifies the difference between measured and expected flow with a novel metric, flow split deviation (FSD). FSD was devised to give a quantitative value for the likelihood of arterial bleeding and validated in human upper extremities. We used ultrasound to demonstrate that the power law with k = 2.75 appropriately described the normal brachial artery bifurcation geometry and adequately determined the expected normal flows. Our metric was then applied to three-dimensional (3-D) computational models of forearm bleeding and on dialysis patients undergoing surgical construction of wrist arteriovenous fistulas. Computational models showed that larger sized arterial defects produced larger flow deviations. FSD values were statistically higher (paired t-test) for arms with fistulas than those without, with average FSDs of 0.41 ± 0.12 and 0.047 ± 0.021 (mean ± SD), respectively. The average of the differences was 0.36 ± 0.12 (mean ± SD).

View details for DOI 10.1016/j.ultrasmedbio.2011.12.016

View details for Web of Science ID 000301181300018

View details for PubMedID 22341050

Abstract

As endovascular treatment of abdominal aortic aneurysms (AAAs) gains popularity, it is becoming possible to treat certain challenging aneurysmal anatomies with endografts relying on suprarenal fixation. In such anatomies, the bare struts of the device may be placed across the renal artery ostia, causing partial obstruction to renal artery blood flow. Computational fluid dynamics (CFD) was used to simulate blood flow from the aorta to the renal arteries, utilizing patient-specific boundary conditions, in three patient models and calculate the degree of shear-based blood damage (hemolysis). We used contrast-enhanced computed tomography angiography (CTA) data from three AAA patients who were treated with a novel endograft to build patient-specific models. For each of the three patients, we constructed a baseline model and endoframe model. The baseline model was a direct representation of the patient's 30-day post-operative CTA data. This model was then altered to create the endoframe model, which included a ring of metallic struts across the renal artery ostia. CFD was used to simulate blood flow, utilizing patient-specific boundary conditions. Pressures, flows, shear stresses, and the normalized index of hemolysis (NIH) were quantified for all patients. The overall differences between the baseline and endoframe models for all three patients were minimal, as measured though pressure, volumetric flow, velocity, and shear stress. The average NIH across the three baseline and endoframe models was 0.002 and 0.004, respectively. Results of CFD modeling show that the overall disturbance to flow caused by the presence of the endoframe struts is minimal. The magnitude of the NIH in all models was well below the accepted design and safety threshold for implantable medical devices that interact with blood flow.

View details for DOI 10.1115/1.4005850

View details for Web of Science ID 000302582600003

View details for PubMedID 22482670

Abstract

Renal sympathetic hyperactivity is associated with hypertension, a leading cause of mortality worldwide. Renal sympathetic denervation via the Symplicity Catheter System has been shown to decrease blood pressure by 33/11 mmHg by 6 months, with no radiofrequency (RF)-related adverse sequelae visible by CT/MR angiography or renal duplex ultrasound 6 months after the procedure. Here, we present preclinical work predating those clinical results. We performed therapeutic renal sympathetic denervation in a swine animal model to characterize the vascular safety and healing response 6 months after renal denervation therapy.In December 2007, seven domestic swine received a total of 32 radiofrequency ablations via the Symplicity Catheter System and were euthanatized 6 months later. Renal angiography was done before, immediately after, and 6 months after procedure. The renal vessels were examined histologically with H&E and Movat pentachrome stains to identify evidence of vascular and neural injury. The kidneys and urinary system were also examined for evidence of gross and microscopic abnormalities.Renal nerve injury involved primarily nerve fibrosis, replacement of nerve fascicles with fibrous connective tissue, and thickening of the epineurium and perineurium. Renal arterial findings included fibrosis of 10-25% of the total media and underlying adventitia, with mild disruption of the external elastic lamina. No significant smooth muscle hyperplasia or inflammatory components were observed. There was no renal arterial stenosis or thrombosis observed by angiography or histology. No gross or microscopic device-related abnormalities were noted in the kidney, surrounding stroma, or urinary bladder.In a swine model, renal denervation via the Symplicity Catheter System resulted in no clinically significant adverse renal artery or renal findings 6 months after the procedure. This is corroborated by the vascular safety profile demonstrated in subsequent human clinical studies.

View details for DOI 10.1007/s00392-011-0346-8

View details for Web of Science ID 000297364000006

View details for PubMedID 21796327

Abstract

To determine the risk of aneurysm rupture in patients with persisting proximal type Ia endoleaks following endovascular aneurysm repair (EVAR) in comparison to the risk of rupture of untreated abdominal aortic aneurysms (AAA) of similar size.Among 400 patients who where treated with EVAR from 1996 to 2003 at a single center, 21 (5.3%) patients (13 men; mean age 78.0±5.0 years, range 67-86) with large (?5.5 cm) aneurysms had imaging evidence of type Ia endoleaks that persisted >10 months (type Ia group) despite secondary endovascular treatment. These patients were compared to 24 untreated AAA patients (17 men; mean age 73.8±5.2 years, range 64-88) with large aneurysms from a separate geographic region with a well-established aneurysm treatment program before EVAR became available (1990-1998).There were no significant differences between the type Ia and the untreated AAA patients with regard to age (79±8 vs. 74±5 years), gender (38% vs. 29% women), baseline aneurysm diameter (6.1±0.7 vs. 6.4±0.9 cm), or length of follow-up (32±23 vs. 29±40 months). During the follow-up period, the rate of aneurysm enlargement was significantly lower in type Ia patients (0.19 cm/y) than in untreated AAA patients (0.54 cm/y, p?=?0.03). One (4.8%) patient with a persisting type Ia endoleak and 2-cm aneurysm enlargement (0.8 cm/y) had aneurysm rupture after 2.5 years, while 12 (50%) of the 24 untreated aneurysms ruptured (p?=?0.001), which was the primary cause of death in this group. The rupture rate was 1.8 per 100 patient-years in the type Ia group and 20.7 per 100 patient-years in the untreated AAA group. Aneurysm-related mortality was significantly reduced in the type Ia group compared to the untreated AAA group at 36 months (11% vs. 52%, p?=?0.004). In the multivariate analysis, factors associated with death were an untreated AAA (odds ratio 97, p?=?0.004), female gender (odds ratio 9.7, p?=?0.02), and baseline aneurysm size (odds ratio 4.7/cm, p?=?0.03).This study suggests that EVAR may reduce the risk of rupture and aneurysm-related death despite the presence of a persisting type Ia endoleak. This finding is limited to patients with aortic endografts that are in good position. The mechanism of protection from rupture is unclear but may be related to reducing the rate of aneurysm enlargement.

View details for Web of Science ID 000295964400010

View details for PubMedID 21992639

Abstract

The ability to stimulate mammalian cells with light has significantly changed our understanding of electrically excitable tissues in health and disease, paving the way toward various novel therapeutic applications. Here, we demonstrate the potential of optogenetic control in cardiac cells using a hybrid experimental/computational technique. Experimentally, we introduced channelrhodopsin-2 into undifferentiated human embryonic stem cells via a lentiviral vector, and sorted and expanded the genetically engineered cells. Via directed differentiation, we created channelrhodopsin-expressing cardiomyocytes, which we subjected to optical stimulation. To quantify the impact of photostimulation, we assessed electrical, biochemical, and mechanical signals using patch-clamping, multielectrode array recordings, and video microscopy. Computationally, we introduced channelrhodopsin-2 into a classic autorhythmic cardiac cell model via an additional photocurrent governed by a light-sensitive gating variable. Upon optical stimulation, the channel opens and allows sodium ions to enter the cell, inducing a fast upstroke of the transmembrane potential. We calibrated the channelrhodopsin-expressing cell model using single action potential readings for different photostimulation amplitudes, pulse widths, and frequencies. To illustrate the potential of the proposed approach, we virtually injected channelrhodopsin-expressing cells into different locations of a human heart, and explored its activation sequences upon optical stimulation. Our experimentally calibrated computational toolbox allows us to virtually probe landscapes of process parameters, and identify optimal photostimulation sequences toward pacing hearts with light.

View details for DOI 10.1016/j.bpj.2011.08.004

View details for Web of Science ID 000295197300006

View details for PubMedID 21943413

Abstract

To evaluate the biomechanical and hemodynamic forces acting on the intermodular junctions of a multi-component thoracic endograft and elucidate their influence on the development of type III endoleak due to disconnection of stent-graft segments.Three-dimensional computer models of the thoracic aorta and a 4-component thoracic endograft were constructed using postoperative (baseline) and follow-up computed tomography (CT) data from a 69-year-old patient who developed type III endoleak 4 years after stent-graft placement. Computational fluid dynamics (CFD) techniques were used to quantitate the displacement forces acting on the device. The contact stresses between the different modules of the graft were then quantified using computational solid mechanics (CSM) techniques. Lastly, the intermodular junction frictional stability was evaluated using a Coulomb model.The CFD analysis revealed that curvature and length are key determinants of the displacement forces experienced by each endograft and that the first 2 modules were exposed to displacement forces acting in opposite directions in both the lateral and longitudinal axes. The CSM analysis revealed that the highest concentration of stresses occurred at the junction between the first and second modules of the device. Furthermore, the frictional analysis demonstrated that most of the surface area (53%) of this junction had unstable contact. The predicted critical zone of intermodular stress concentration and frictional instability matched the location of the type III endoleak observed in the 4-year follow-up CT image.The region of larger intermodular stresses and highest frictional instability correlated with the zone where a type III endoleak developed 4 years after thoracic stent-graft placement. Computational techniques can be helpful in evaluating the risk of endograft migration and potential for modular disconnection and may be useful in improving device placement strategies and endograft design.

View details for Web of Science ID 000294212500020

View details for PubMedID 21861748

Abstract

To develop an arterial injury model for testing hemostatic devices at well-defined high and low bleeding rates.A side-hole arterial injury was created in the carotid artery of sheep. Shed blood was collected in a jugular venous reservoir and bleeding rate at the site of arterial injury was controlled by regulating outflow resistance from the venous reservoir. Two models were studied: uncontrolled exsanguinating hemorrhage and bleeding at controlled rates with blood return to maintain hemodynamic stability. Transcutaneous Duplex ultrasound was used to characterize ultrasound signatures at various bleeding rates.A 2.5 mm arterial side-hole resulted in exsanguinating hemorrhage with an initial bleeding rate of 400 ml/min which, without resuscitation, decreased to below 100 ml/min in 5 minutes. After 17 minutes, bleeding from the injury site stopped and the animal had lost 60% of total blood volume. Reinfusion of shed blood maintained normal hemodynamics and both high and low bleeding rates could be maintained without hemorrhagic shock. Bleeding rate at the arterial injury site was held at 395±78 ml/min for 8 minutes, 110±11 ml/min for 15 minutes, and 12±1 ml/min for 12 minutes. Doppler flow signatures at the site of injury were characterized by high peak and end-diastolic flow velocities at the bleeding site which varied with the rate of hemorrhage.We have developed a hemodynamically stable model of acute arterial injury which can be used to evaluate diagnostic and treatment methods focused on control of the arterial injury site.

View details for DOI 10.2478/v10035-011-0001-0

View details for PubMedID 22166236

Abstract

To study the role of cell-extracellular matrix (ECM) interactions, microscale approaches provide the potential to perform high throughput assessment of the effect of the ECM microenvironment on cellular function and phenotype. Using a microscale direct writing (MDW) technique, we characterized the generation of multicomponent ECM microarrays for cellular micropatterning, localization and stem cell fate determination. ECMs and other biomolecules of various geometries and sizes were printed onto epoxide-modified glass substrates to evaluate cell attachment by human endothelial cells. The endothelial cells displayed strong preferential attachment to the ECM patterned regions and aligned their cytoskeleton along the direction of the micropatterns. We next generated ECM microarrays that contained one or more ECM components (namely gelatin, collagen IV and fibronectin) and then cultured murine embryonic stem cell (ESCs) on the microarrays. The ESCs selectively attached to the micropatterned features and expressed markers associated with a pluripotent phenotype, such as E-cadherin and alkaline phosphatase, when maintained in growth medium containing leukemia inhibitory factor. In the presence of the soluble factors retinoic acid and bone morphogenetic protein-4 the ESCs differentiated towards the ectodermal lineage on the ECM microarray with differential ECM effects. The ESCs cultured on gelatin showed significantly higher levels of pan cytokeratin expression, when compared with cells cultured on collagen IV or fibronectin, suggesting that gelatin preferentially promotes ectodermal differentiation. In summary, our results demonstrate that MDW is a versatile approach to print ECMs of diverse geometries and compositions onto surfaces, and it is amenable to the generation of multicomponent ECM microarrays for stem cell fate determination.

View details for DOI 10.1016/j.actbio.2010.06.033

View details for Web of Science ID 000284385300018

View details for PubMedID 20601236

Abstract

New detection methods for vascular injuries can augment the usability of an ultrasound (US) imager in trauma settings. The goal of this study was to evaluate a potential-detection strategy for internal bleeding that employs a well-established theoretical biofluid model, the power law. This law characterizes normal blood-flow rates through an arterial tree by its bifurcation geometry. By detecting flows that deviate from the model, we hypothesized that vascular abnormalities could be localized. We devised a bleed metric, flow-split deviation (FSD), that quantified the difference between patient and model blood flows at vessel bifurcations. Femoral bleeds were introduced into ten rabbits (?5 kg) using a cannula attached to a variable pump. Different bleed rates (0% as control, 5%, 10%, 15%, 20%, 25%, and 30% of descending aortic flow) were created at two physiological states (rest and elevated state with epinephrine). FSDs were found by US imaging the iliac arteries. Our bleed metric demonstrated good sensitivity and specificity at moderate bleed rates; area under receiver-operating characteristic curves were greater than 0.95 for bleed rates 20% and higher. Thus, FSD was a good indicator of bleed severity and may serve as an additional tool in the US bleed detection.

View details for DOI 10.1109/TBME.2010.2058803

View details for Web of Science ID 000284360100009

View details for PubMedID 20639172

Abstract

Although repair of large abdominal aortic aneurysms (AAAs) is well accepted, randomized clinical trials have failed to demonstrate benefit for early surgical repair of small aneurysms compared with surveillance. Endovascular repair has been shown to be safer than open surgical repair in patients with large aneurysms, prompting a randomized trial of early endovascular repair vs surveillance in patients with small aneurysms.We randomly assigned 728 patients (13.3% women; mean age, 71 +/- 8 years) with 4 to 5 cm AAAs to early endovascular repair (366 patients) or ultrasound surveillance (362 patients). Rupture or aneurysm-related death and overall mortality in the two groups were compared during a mean follow-up of 20 +/- 12 months.Among patients randomized to treatment, 89% underwent aneurysm repair. Among patients randomized to surveillance, 31% underwent aneurysm repair during the course of the study. After a mean follow-up of 20 +/- 12 months (range, 0-41 months), 15 deaths had occurred in each group (4.1%). The unadjusted hazard ratio (95% confidence interval) for mortality after early endovascular repair was 1.01 (0.49-2.07, P = .98). Aneurysm rupture or aneurysm-related death occurred in two patients in each group (0.6%). The unadjusted hazard ratio was 0.99 (0.14-7.06, P = .99) for early endovascular repair.Early treatment with endovascular repair and rigorous surveillance with selective aneurysm treatment as indicated both appear to be safe alternatives for patients with small AAAs, protecting the patient from rupture or aneurysm-related death for at least 3 years.

View details for DOI 10.1016/j.jvs.2009.10.113

View details for Web of Science ID 000277216000001

View details for PubMedID 20304589

Abstract

An 82-year-old female with a history of right carotid endarterectomy with patch closure 12 years prior presents with a pulsatile right neck mass with skin erosion and bleeding. The patient had been previously evaluated but refused the surgical intervention because a median sternotomy was recommended to obtain adequate proximal control. Her aneurysm was successfully repaired using a combination of open and endovascular method. The repair was performed through a right-hand side anterior sternocleidomastoid neck incision, and proximal vascular control was obtained with an 8.5-mm balloon positioned under fluoroscopic guidance via a femoral puncture.

View details for DOI 10.1177/1538574409347395

View details for Web of Science ID 000273791100013

View details for PubMedID 19828583

Abstract

The geometry and dynamics of the vena cava are poorly understood and current knowledge is largely based on qualitative data. The purpose of this study is to quantitate the dimensional changes that occur in the infrarenal inferior vena cava (IVC), in response to changes in intravascular volume.IVC dimensions were measured at 1 cm and 5 cm below the renal veins, on serial contrasted computed tomographic (CT) scans, in 30 severely injured trauma patients during hypovolemic (admission) and fluid resuscitated (follow-up) states. Changes in volume of the infrarenal segment were calculated and correlated with changes in IVC diameter and orientation. The orientation of the infrarenal caval segment was quantified as the angulation of the major axis from the horizontal. A representation of the IVC diameter, as would be seen on standard anterior-posterior venographic imaging, was determined by projecting the CT image of the major axis onto a coronal plane. CT representations of venographic diameters were compared with measurements of the true major axis to assess accuracy of venograms for caval sizing and filter selection.All patients had evidence of a collapsed IVC (<15 mm minor axis dimension) on admission. Mean time between admission and follow-up CT was 49.5 (range: 1-202) days. The volume of the infrarenal segment increased more than twofold with resuscitation, increasing from 6.9 +/- 2.2 (range: 3.1-12.4) mL on admission, to 15.7 +/- 5.0 (range: 9.2-28.5) mL on follow-up (P < .01). At both 1 and 5 cm below the renal veins, the IVC expanded anisotropically such that the minor axis expanded up to five times its initial size accommodating 84% of the increased volume of the segment, while only small diameter changes were observed in the major axis accounting for less than 5% of the volume increase (P < .001). Further, the IVC was left-anterior-oblique in all patients, with the major axis 26 degrees off the horizontal on average. This orientation did not change significantly with volume resuscitation (P > 0.5). The obliquity of the IVC resulted in significant underestimation of caval size of up to 6.8 mm, when using the venographic representation for sizing instead of the true major axis (P < 0.001).In response to changes in intravascular volume, the IVC undergoes profound anisotropic dimensional changes, with greater displacement seen in the minor axis. In addition, the IVC is oriented left-anterior oblique and caval orientation is not altered by changes in volume status. IVC obliquity may result in underestimation of caval size by anterior-posterior venogram.

View details for DOI 10.1016/j.jvs.2009.05.012

View details for Web of Science ID 000270404500019

View details for PubMedID 19660896

Abstract

Open surgical repair after failed endovascular aneurysm repair (EVAR) usually involves complete endograft removal and replacement with a prosthetic surgical graft. This is associated with significant morbidity and mortality. We have used an alternative strategy focused on limiting the magnitude of surgical repair by preserving the functioning portion of the endograft and avoiding aortic cross-clamping, when possible.Between January 2000 and 2008, patients requiring delayed conversion after EVAR at our institution were managed with (1) complete endograft preservation and external wrap of the aortic neck to secure a proximal seal, or (2) partial endograft removal with interposition grafting from the infrarenal aortic neck to the remaining endograft. Records of all patients were retrospectively reviewed for demographics, operative details, and outcomes.During this time, 12 patients were treated with delayed open surgical conversion. The indication for conversion in all patients was a type I endoleak with aneurysm enlargement not amendable to percutaneous intervention. Mean age was 81 +/- 6.2 years (range, 61-90 years). Average time to conversion was 44.7 months (range, 7-80 months). Complete endograft preservation was attempted in eight patients and was successful in six (75%). The two patients that failed this approach, as well as four additional patients who were not candidates for this approach, underwent partial endograft excision and replacement with an interposition graft sutured to the remaining portion of the stent graft. Complete endograft removal was not required in any patients. There was one post-operative mortality (8.3%) and one significant post-operative morbidity (8.3%). Mean intensive care unit and hospital stays were 2.8 +/- 3.9 days (range, 1-15 days) and 8.4 +/- 5.8 days (range, 3-26 days), respectively.Open surgical repair of failed EVAR can be accomplished with preservation of all or a significant portion of the endograft in most patients. This may limit the magnitude of the repair procedure and may reduce morbidity and mortality.

View details for DOI 10.1016/j.jvs.2009.05.024

View details for Web of Science ID 000270404500002

View details for PubMedID 19786235

Abstract

To examine the 4-year outcomes from Carotid Revascularization using Endarterectomy or Stenting Systems (CaRESS) in light of the current reimbursement guidelines for carotid artery stenting (CAS) from the Centers for Medicare and Medicaid Services (CMS).CaRESS was designed as a prospective, nonrandomized comparative cohort study of a broad-risk population of symptomatic and asymptomatic patients with carotid stenosis. In all, 397 patients (247 men; mean age 71 years, range 43-89) were enrolled and underwent carotid endarterectomy (CEA; n = 254) or protected CAS (n = 143). More than 90% of patients had >75% stenosis; two thirds were asymptomatic. The primary endpoints included (1) all-cause mortality, (2) any stroke, and (3) myocardial infarction (MI), as well as the composite endpoints of (4) death and any nonfatal stroke and (5) death, nonfatal stroke, and MI. The secondary endpoints were restenosis, repeat angiography, and carotid revascularization. All patients were classified with respect to surgical risk, symptom status, and stenosis grade based on criteria published by the CMS. In addition, separate analyses were performed comparing genders and octogenarians to those <80 years old.No significant differences in the primary outcome measures were found between the CEA and CAS groups in the 4-year analysis. The incidences of any stroke at 4 years were 9.6% for CEA and 8.6% for CAS (p = 0.444); when combined with death, the composite death/nonfatal stroke rates were 26.5% for CEA versus 21.8% for CAS (p = 0.361). The composite endpoint of death, nonfatal stroke, and MI at 4 years was 27.0% in CEA versus 21.7% in CAS (p = 0.273) patients. The secondary endpoints of restenosis (p = 0.014) and repeat angiography (p = 0.052) were higher in the CAS arm. There were no differences in any of the subgroups stratified according the CMS guidelines or in the gender comparison. Four-year incidences of death/nonfatal stroke and death/nonfatal stroke/MI were higher in the CEA arm among patients <80 years of age (p = 0.049 and p = 0.030, respectively). There were no significant differences between these incidences in the octogenarian subgroup.The risk of death or nonfatal stroke 4 years following CAS with distal protection is equivalent to CEA in a broad category of patients with carotid stenosis. There were no significant differences in stroke or mortality rates between high-risk and non-high-risk patients and no differences in outcomes between symptomatic and asymptomatic patients. After 4 years, CAS had a 2-fold higher restenosis rate compared to CEA. The risk of death/stroke or death/stroke/MI appears to be higher following CEA than CAS among patients <80 years of age, yet there is no statistically significant relationship between death, stroke, or MI among octogenarians.

View details for Web of Science ID 000269463900001

View details for PubMedID 19702339

Abstract

Chronic mesenteric ischemia is a rare disorder that has traditionally been treated with open surgical revascularization (OR). Endovascular revascularization (ER) has recently gained popularity as an alternative modality of treatment; however, OR is still predominantly used. This study aimed at comparing the outcomes of these two treatment modalities. The literature was searched using the MEDLINE database through the PubMed search engine for relevant articles that compared the outcomes after OR and ER for chronic mesenteric ischemia. Review of the selected articles revealed that patients had lower postoperative mortality and morbidity, and shorter intensive care unit and hospital stay after ER. However, early and long-term symptomatic relief and significantly lower restenosis rate were characteristic of OR. Although no level 1 evidence governs the treatment of chronic mesenteric ischemia, the durability and efficacy of OR is such that this modality should remain the procedure of choice for patients who are fit or whose fitness could be improved before surgery. For unfit patients, or those with short life expectancy, ER is preferable owing to its minimally invasive nature and reduced postoperative mortality and morbidity. Randomized controlled studies are needed to compare the long-term durability and efficacy of ER to those of OR.

View details for Web of Science ID 000271955000010

View details for PubMedID 19455085

Abstract

To determine the effect of curvature on the magnitude and direction of displacement forces acting on aortic endografts in 3-dimensional (3D) computational models.A 3D computer model was constructed based on magnetic resonance angiography data from a patient with an infrarenal aortic aneurysm. Computational fluid dynamics tools were used to simulate realistic flow and pressure conditions of the patient. An aortic endograft was deployed in the model, and the displacement forces acting on the endograft were calculated and expressed in Newtons (N). Additional models were created to determine the effects of reducing endograft curvature, neck angulation, and iliac angulation on displacement forces.The aortic endograft had a curved configuration as a result of the patient's anatomy, with curvature in the anterolateral direction. Total displacement force acting on the endograft was 5.0 N, with 28% of the force in a downward (caudal) direction and 72% of the force in a sideways (anterolateral) direction. Elimination of endograft curvature (planar graft configuration) reduced total displacement force to 0.8 N, with the largest component of force (70%) acting in the sideways direction. Straightening the aortic neck in the curved endograft configuration reduced the total force acting on the endograft to 4.2 N, with a reduction of the sideways component to 55% of the total force. Straightening the iliac limbs of the endograft reduced the total force acting on the endograft to 2.1 N but increased the sideways component to 91% of the total force.The largest component of the force acting on the aortic endograft is in the sideways direction, with respect to the blood flow, rather than in the downward (caudal) direction as is commonly assumed. Increased curvature of the aortic endograft increases the magnitude of the sideways displacement force. The degree of angulation of the proximal and distal ends of the endograft influence the magnitude and direction of displacement force. These factors may have a significant influence on the propensity of endografts to migrate in vivo.

View details for Web of Science ID 000268117500004

View details for PubMedID 19642787

Abstract

To assess 3-dimensional (3D) pulsatile displacement forces (DF) acting on thoracic endografts using 3D computational techniques.A novel computational method to quantitate the pulsatile 3D flow and pressure fields and aortic wall dynamics in patient-specific anatomical models based on cardiac-gated computed tomography (CT) scans was used to construct simulations of the proximal and mid-descending thoracic aorta. Endografts of varying lengths and diameters were implanted in these patient-specific models. The magnitude and direction of the DF vector were calculated and expressed in Newtons (N). This DF included the effects of both the pressure and shearing stresses of blood.The magnitude of DF increased with endografts of increasing diameter and length. A 36-mm endograft in the mid-descending aorta had a mean DF of 21.7 N with a peak systolic DF of 27.8 N and an end-diastolic DF of 16.7 N. Conversely, a 30-mm endograft in the proximal descending aorta had a mean DF of 14.9 N, with peak systolic and end-diastolic DFs of 18.9 and 11.5, respectively. The orientation of the DF acting on the endograft varied depending on aortic angulation and tortuosity; in general, the vector was perpendicular to the greater curvature of the endograft rather than along the downstream longitudinal centerline axis of the aorta as is commonly believed. The DF vector pointed primarily in the cranial direction for the proximal descending endograft and in the sideways direction for the mid-descending endograft simulation. Furthermore, it was shown that elevated pressure plays an important role in the magnitude and direction of DF; an increase in mean blood pressure resulted in an approximately linearly proportional increase in DF.The orientation of the DF varies depending on curvature and location of the endograft, but in all instances, it is in the cranial rather than caudal direction on axial imaging. This is counter to the intuitive notion that displacement forces act in the downward direction of blood flow. Therefore, we postulate that migration of thoracic endografts may be different from abdominal endografts since it may involve upward rather than downward movement of the graft. Computational methods can enhance the understanding of the magnitude and orientation of the loads experienced in vivo by thoracic aortic endografts and therefore improve their design and performance.

View details for Web of Science ID 000268117500015

View details for PubMedID 19642798

Abstract

This study investigated the importance of iliac fixation to secure endograft fixation.Computed tomography (CT) scans of patients who underwent endovascular aneurysm repair with an endoprosthesis of great columnar strength (Talent stent graft) were analysed retrospectively. Patients were enrolled consecutively between June 2000 and January 2007 and prospectively followed up with serial CT imaging. The superior mesenteric artery was used as a reference point to determine endograft migration (centerline endograft displacement of >or=10mm). Proximal and distal fixation lengths were defined as the length of the endograft that was in full apposition to the aortic neck or common iliac arteries, respectively.Proximal endograft migration occurred in 32 of 154 patients (21%) at a follow-up duration of 32+/-14 months; 13 migrations required treatment (8%). Migration was more frequent in patients treated with aorto-uniiliac devices than bifurcation devices (p<0.008). The migrator and non-migrator groups had similar demographic and abdominal aortic aneurysm (AAA) characteristics. The migrator group had significantly shorter proximal (30+/-12 mm vs. 41+/-13 mm, P<0.001) and distal endograft fixation lengths (31+/-18 mm vs. 47+/-15 mm, P<0.001). By multivariate regression analysis, proximal and distal endograft fixations were significant predictors for endograft migration at follow-up (P<0.001).Iliac endograft fixation, along with proximal fixation, is a significant predictor for endograft migration.

View details for DOI 10.1016/j.ejvs.2009.03.001

View details for Web of Science ID 000267585100008

View details for PubMedID 19345632

Abstract

Ruptured abdominal aortic aneurysm (RAAA) is the most common and devastating complication affecting a patient with abdominal aortic aneurysm (AAA). Despite advances in surgery and critical care, the mortality rate associated with RAAA remains largely unchanged. Emergency open repair is the gold standard conventional treatment of RAAA but is associated with a high mortality rate. The physiologic challenges associated with general anaesthetic induction such as loss of the sympathetic vasoconstrictor tone with consequent hypotension, and the anatomic challenges associated with external aortic cross-clamping such as calcification, friability, or poor visualisation of the aneurysm neck, have led to the adoption of endovascular techniques in the surgical treatment of RAAA. Promising results of endovascular repair of ruptured abdominal aortic aneurysm (REVAR) have been reported. In addition, the provision of endovascular aortic control by inflating a compliant aortic occlusion balloon (AOB) proximal to the ruptured aneurysm, as an internal aortic clamp, has been successfully used in haemodynamically unstable patients undergoing either REVAR or emergency open repair of RAAA. An AOB is inserted under local anaesthesia and can be introduced through either the transbrachial or the transfemoral routes, each with its own advantages and disadvantages. This review aimed at providing an up-to-date overview of the current knowledge concerning endovascular proximal aortic control using an AOB with emphasis on the rationale, position, benefits, and drawbacks of its use.

View details for Web of Science ID 000270830000014

View details for PubMedID 19282811

Abstract

We report the first utilization of time-resolved three-dimensional phase contrast magnetic resonance imaging, termed 4D flow, to image a type I endoleak after endovascular aneurysm repair. The combination of 4D flow and a traditional magnetic resonance angiogram can aid in the accurate detection and characterization of endoleaks by combining the three-dimensional resolution of cross-sectional imaging with the temporally resolved velocity data of Doppler ultrasound.

View details for DOI 10.1016/j.jvs.2009.01.010

View details for Web of Science ID 000266681000031

View details for PubMedID 19223146

Abstract

Ruptured abdominal aortic aneurysm (AAA) is one of the most fatal surgical emergencies, with an overall mortality rate of 90%. Most AAAs rupture into the retroperitoneal cavity, which results in the classical triad of pain, hypotension, and a pulsatile mass. However, this triad is seen in only 25-50% of patients, and many patients with ruptured AAA are misdiagnosed. It is likely that different sites of rupture of AAA determine a variety of common and uncommon clinical presentations, the recognition of which can save many lives. This article reviews the different sites of rupture of infrarenal AAA and explores the evidence behind the various clinical presentations seen in patients with ruptured AAA.

View details for DOI 10.1136/pgmj.2008.074666

View details for Web of Science ID 000266974900009

View details for PubMedID 19520879

Abstract

We developed a novel method using anatomic markers along the thoracic aorta to accurately quantify longitudinal and circumferential cyclic strain in nondiseased thoracic aortas during the cardiac cycle and to compute age-related changes of the human thoracic aorta.Changes in thoracic aorta cyclic strains were quantified using cardiac-gated computed tomography image data of 14 patients (aged 35 to 80 years) with no visible aortic pathology (aneurysms or dissection). We measured the diameter and circumferential cyclic strain in the arch and descending thoracic aorta (DTA), the longitudinal cyclic strain along the DTA, and changes in arch length and motion of the ascending aorta relative to the DTA. Diameters were computed distal to the left coronary artery, proximal and distal to the brachiocephalic trunk, and distal to the left common carotid, left subclavian, and the first and seventh intercostal arteries. Cyclic strains were computed using the Green-Lagrange strain tensor. Arch length was defined along the vessel centerline from the left coronary artery to the first intercostal artery. The length of the DTA was defined along the vessel centerline from the first to seventh intercostal artery. Longitudinal cyclic strain was quantified as the difference between the systolic and diastolic DTA lengths divided by the diastolic DTA length. Comparisons were made between seven younger (age, 41 +/- 7 years; 5 men) and seven older (age, 68 +/- 6 years; 5 men) patients.The average increase of diameters of the thoracic aorta was 14% with age from the younger to the older (mean age, 41 vs 68 years) group. The average circumferential cyclic strain of the thoracic aorta decreased by 55% with age from the younger to the older group. The longitudinal cyclic strain decreased with age by 50% from the younger to older group (2.0% +/- 0.4% vs 1.0% +/- 1%, P = .03). The arch length increased by 14% with age from the younger to the older group (134 +/- 17 mm vs 152 +/- 10 mm, P = .03).The thoracic aorta enlarges circumferentially and axially and deforms significantly less in the circumferential and longitudinal directions with increasing age. To our knowledge, this is the first quantitative description of in vivo longitudinal cyclic strain and length changes for the human thoracic aorta, creating a foundation for standards in reporting data related to in vivo deformation and may have significant implications in endoaortic device design, testing, and stability.

View details for DOI 10.1016/j.jvs.2008.11.056

View details for Web of Science ID 000264757700041

View details for PubMedID 19341890

Abstract

Endovascular devices have been designed by trial and error, with bench and animal testing followed by human clinical trials to determine whether the devices are safe and effective. Despite remarkable advances over the past 15 years, there are persistent concerns regarding the long-term durability of endovascular devices. This may be due to deficiencies in device design, which has lagged behind other industries in adopting computational methods that are now routinely used to design, develop, and test new aircraft and automobiles. Similar computational design and failure mode simulations that evaluate performance under stress conditions have not been widely applied in the development of endovascular devices. Advances in medical imaging and computational modeling now allow simulation of physiological conditions in patient-specific 3-dimensional vascular models, which can provide a framework to design and test the next generation of endovascular devices. This modeling will allow the prospective design of devices that can withstand the force variations in the cardiovascular system that occur during bending, coughing, and varying degrees of exercise, as well as the extremes encountered during sudden impact in contact sports. Utilization of computational design methodology that takes into consideration the physiology of the cardiovascular system will improve future endovascular devices so that they are safer and more effective and durable.

View details for DOI 10.1583/08-2640.1

View details for PubMedID 19317584

View details for DOI 10.1161/CIRCULATIONAHA.108.191176

View details for Web of Science ID 000261948700026

View details for PubMedID 19106408

Abstract

Acute mesenteric ischaemia is a catastrophic abdominal emergency with an extremely high mortality rate. This article discusses the aetiology, diagnosis and treatment of acute mesenteric ischaemia with emphasis on avoidance of common errors that contribute to the poor outcome inherent to this condition.

View details for Web of Science ID 000262021500019

View details for PubMedID 19186606

Abstract

Acute aortic dissection is one of the most fatal acute cardiovascular disorders that has challenged physicians and surgeons for decades. This article provides an up-to-date overview of the aetiology, pathophysiology, diagnosis and treatment of this condition.

View details for Web of Science ID 000260959900017

View details for PubMedID 19069262

Abstract

To determine the safety and performance of a new inferior vena cava (IVC) filter in an ovine model and evaluate the retrievability at 5 weeks.The Crux Vena Cava Filter (VCF) is composed of 2 nitinol spiral supports with a polymeric filter suspended between them. Retrieval tails on each end facilitate retrieval. Twelve filters were placed in the infrarenal IVCs of 12 sheep. The vessels were imaged pre and post deployment to assess acute device performance. At 5 weeks, the vessels were re-imaged to evaluate continued device performance and vessel integrity. Nine of 12 filters were retrieved, and the animals were returned to their housing. The other 3 animals were sacrificed, and the filters and vessels were processed for gross and histological examination. At 9 weeks, 4 weeks after filter retrieval, vessel integrity of the remaining 9 animals was again assessed under fluoroscopy. The animals were sacrificed, and the IVCs were explanted for study.All 12 filters were implanted without complications at the intended deployment site and remained fixed over the implantation period. At 5 weeks, the filters intended for recovery were successfully retrieved, with a mean capture time of 9.6+/-13.7 minutes. There were no complications during the 4-week follow-up after filter retrieval. Post-retrieval imaging at 5 and 9 weeks showed no visible signs of vessel wall damage. Histological study of 3 explanted vessels and filters revealed slight neointima encapsulation of the filter elements and minimal incorporation. Gross examination of the post-retrieval vessel walls after the 4-week healing period showed minimal superficial vessel damage; histology showed minimal residual signs of hemorrhage, with little to no inflammatory reaction.The Crux VCF was deployed and safely retrieved without incident at 5 weeks in an animal model. There was no significant damage seen to the IVCs 1 month after filter retrieval.

View details for Web of Science ID 000257093100006

View details for PubMedID 18540703

Abstract

To determine if lateral movement of an aortic endograft 1 year following endovascular abdominal aortic aneurysm (AAA) repair is an indicator of endograft instability and can serve as a predictor of late adverse events.The records of 60 high-risk AAA patients (52 men, 8 women; mean age 74 years) who were treated with infrarenal (n = 38) or suprarenal (n = 22) endografts and had serial computed tomograms (CT) over > or =12 months were analyzed. Postimplantation and 1-year CT scans were compared, and changes in endograft position within the aneurysm sac [lateral movement (LM) versus no lateral movement (NM)] were measured using a vertebral body reference point. Longitudinal endograft movement was measured with respect to the superior mesenteric artery along the aortic centerline axis. Long-term adverse event rates (endoleaks, secondary procedures, conversion, rupture, and death) were assessed.One year after endograft implantation, LM > or =5 mm was present in 16 (27%) patients; 44 (73%) endografts demonstrated no lateral movement. LM patients had larger aneurysms (6.5+/-1.5 versus 5.6+/-0.9 cm, p = 0.02) and a longer endograft-to-hypogastric artery length (p = 0.01) than NM patients. There were no significant differences between patients treated with infrarenal and suprarenal endografts. At 1 year, longitudinal migration > or =10 mm occurred in 5 (31%) of the LM patients versus 2 (5%) in the NM cohort (p<0.0001). There were no significant differences in adverse event rates between LM and NM at 1 year. However, during long-term follow-up (mean 54+/-26 months, range 12-102), 8 (50%) LM patients developed a type I endoleak versus 8 (18%) NM patients (p = 0.02), and 12 (75%) LM patients required a secondary procedure versus 9 (20%) NM patients (p = 0.0002). One (6%) LM patient experienced aneurysm rupture and 2 (13%) other LM patients underwent conversion to open repair.Lateral endograft movement within the aneurysm sac at 1 year is associated with increased risk of late adverse events and was at least as good a predictor of these complications as was longitudinal migration.

View details for Web of Science ID 000257093100012

View details for PubMedID 18540708

Abstract

Changes in arterial wall composition and function underlie all forms of vascular disease. The fundamental structural and functional unit of the aortic wall is the medial lamellar unit (MLU). While the basic composition and organization of the MLU is known, three-dimensional (3D) microstructural details are tenuous, due (in part) to lack of three-dimensional data at micro- and nano-scales. We applied novel electron and confocal microscopy techniques to obtain 3D volumetric information of aortic medial microstructure at micro- and nano-scales with all constituents present. For the rat abdominal aorta, we show that medial elastin has three primary forms: with approximately 71% of total elastin as thick, continuous lamellar sheets, 27% as thin, protruding interlamellar elastin fibers (IEFs), and 2% as thick radial struts. Elastin pores are not simply holes in lamellar sheets, but are indented and gusseted openings in lamellae. Smooth muscle cells (SMCs) weave throughout the interlamellar elastin framework, with cytoplasmic extensions abutting IEFs, resulting in approximately 20 degrees radial tilt (relative to the lumen surface) of elliptical SMC nuclei. Collagen fibers are organized as large, parallel bundles tightly enveloping SMC nuclei. Quantification of the orientation of collagen bundles, SMC nuclei, and IEFs reveal that all three primary medial constituents have predominantly circumferential orientation, correlating with reported circumferentially dominant values of physiological stress, collagen fiber recruitment, and tissue stiffness. This high resolution three-dimensional view of the aortic media reveals MLU microstructure details that suggest a highly complex and integrated mural organization that correlates with aortic mechanical properties.

View details for DOI 10.1016/j.matbio.2007.10.008

View details for Web of Science ID 000254993000003

View details for PubMedID 18248974

Abstract

It is commonly assumed that the aortic wall deforms uniformly and has uniform wall thickness about the circumference. The purpose of this study was to evaluate the aortic wall motion and thickness in the infrarenal aortic neck of patients with abdominal aortic aneurysms who were undergoing endovascular repair (EVAR) and to compare the dynamic measurements of intravascular ultrasonography with the static measurements of computed tomographic angiography (CTA).A total of 25 patients were evaluated before surgery with CTA and three-dimensional reconstructions on a Vitrea workstation, followed by intraoperative assessment of the proximal aortic neck with intravascular ultrasonography (IVUS) before EVAR. Infrarenal aortic neck dimensions on CTA were obtained at 1-mm intervals, but for the purposes of this study all dimensions on CTA were obtained 1 cm below the lowest renal artery. IVUS analysis of the proximal aortic neck was obtained with a 10-second recorded data loop of aortic wall motion. A Digital Imaging and Communications in Medicine viewer was used to view the recorded loop of aortic movement, and each image was captured and then evaluated with a SCION PCI Frame Grabber to determine aortic dimensions and wall thickness. IVUS diameters (250 measurements of each aorta) were recorded through a full continuous cardiac cycle from the epicenter of the lumen (maintaining the left renal vein in its normal anatomic configuration) in an anteroposterior (AP) direction in the area of greatest wall movement and 90 degrees perpendicular to this direction (lateral movement).There was significant variation in infrarenal aortic wall movement about the circumference, with 1.7 +/- 0.6 mm (range, 0.6-2.7 mm) displacement in the AP direction and 0.9 +/- 0.5 mm (range, 0.3-1.5 mm) displacement in the lateral direction (P < .001). Aortic wall thickness was greater in the region of increased AP wall motion than in the area of lesser lateral wall motion (2.3 +/- 0.6 mm vs 1.2 +/- 0.3 mm; P < .001). There was no difference between the IVUS and CTA aortic neck measurements (25.5 vs 25.6 mm; not significant) during the midpoint of the cardiac cycle of IVUS. However, at peak systole, IVUS recorded a greater diameter than CTA (26.4 vs 25.6 mm; P < .001), and at end-diastole, IVUS recorded a smaller diameter than CTA (24.7 vs 25.6 mm; P = .01).The infrarenal neck of aortic aneurysms deforms anisotropically during the cardiac cycle. The greatest displacement is in the AP direction and corresponds with a significantly greater wall thickness in this area. The magnitude of cyclic change in aortic diameter can be as high as 11%. Further evaluation of proximal aortic neck wall motion after EVAR is warranted to determine the interaction of various stent designs and the aortic wall.

View details for DOI 10.1016/j.jvs.2007.06.030

View details for Web of Science ID 000250675700009

View details for PubMedID 17980275

Abstract

To determine whether variations in aortic wall motion exist in mammalian species other than humans and to consider the potential implications of such variations.M-mode ultrasound was used to measure abdominal aortic wall motion in 4 animal species [mice (n=10), rats (n=8), rabbits (n=7), and pigs (n=5)], and humans (n=6). Anterior wall displacement, posterior wall displacement, and diastolic diameter were measured. The ratio of displacement to diameter and cyclic strain were calculated.Body mass varied from 24.1+/-2.4 g (mouse) to 61.8+/-13.4 kg (human); aortic diameter varied from 0.53+/-0.07 mm (mouse) to 1.2+/-1 mm (human). Anterior wall displacement was 2.5 to 4.0 times greater than posterior among the species studied. The ratios of wall displacement to diastolic diameter were similar for the anterior (range 9.40%-11.80%) and posterior (range 2.49%-3.91%) walls among species. The ratio of anterior to posterior displacement (range 2.47-4.03) and aortic wall circumferential cyclic strain (range 12.1%-15.7%) were also similar. An allometric scaling exponent was experimentally derived relating anterior wall (0.377+/-0.032, R2=0.94) and posterior wall (0.378+/-0.037, R2=0.93) displacement to body mass.Abdominal aortic wall dynamics are similar in animals and humans regardless of aortic size, wih more anterior than posterior wall motion. Wall displacement increases linearly with diameter, but allometrically with body mass. These data suggest increased dynamic strain of the anterior wall. Increased strain, corresponding to increased elastin fatigue, may help explain why human abdominal aortic aneurysms initially develop anteriorly. Aortic wall motion should be considered when developing endovascular devices, since asymmetric motion may affect device migration, fixation, and sealing.

View details for Web of Science ID 000248794300021

View details for PubMedID 17696635

Abstract

To evaluate the role of iliac fixation in preventing migration of suprarenal and infrarenal aortic endografts.Quantitative image analysis was performed in 92 patients with infrarenal aortic aneurysms (76 men and 16 women) treated with suprarenal (n = 36) or infrarenal (n = 56) aortic endografts from 2000 to 2004. The longitudinal centerline distance from the superior mesenteric artery to the top of the stent graft was measured on preoperative, postimplantation, and 1-year three-dimensional computed tomographic scans, with movement more than 5 mm considered to be significant. Aortic diameters were measured perpendicular to the centerline axis. Proximal and distal fixation lengths were defined as the lengths of stent-graft apposition to the aortic neck and the common iliac arteries, respectively.There were no significant differences in age, comorbidities, or preoperative aneurysm size (suprarenal, 6.0 cm; infrarenal, 5.7 cm) between the suprarenal and infrarenal groups. However, the suprarenal group had less favorable aortic necks with a shorter length (13 vs 25 mm; P < .0001), a larger diameter (27 vs 24 mm; P < .0001), and greater angulation (19 degrees vs 11 degrees ; P = .007) compared with the infrarenal group. The proximal aortic fixation length was greater in the suprarenal than in the infrarenal group (22 vs 16 mm; P < .0001), with the top of the device closer to the superior mesenteric artery (8 vs 21 mm; P < .0001) as a result of the 15-mm uncovered suprarenal stent. There was no difference in iliac fixation length between the suprarenal and infrarenal groups (26 vs 25 mm; P = .8). Longitudinal centerline stent graft movement at 1 year was similar in the suprarenal and infrarenal groups (4.3 +/- 4.4 mm vs 4.8 +/- 4.3 mm; P = .6). Patients with longitudinal centerline movement of more than 5 mm at 1 year or clinical evidence of migration at any time during the follow-up period comprised the respective migrator groups. Suprarenal migrators had a shorter iliac fixation length (17 vs 29 mm; P = .006) and a similar aortic fixation length (23 vs 22 mm; P > .999) compared with suprarenal nonmigrators. Infrarenal migrators had a shorter iliac fixation length (18 vs 30 mm; P < .0001) and a similar aortic fixation length (14 vs 17 mm; P = .1) compared with infrarenal nonmigrators. Nonmigrators had closer device proximity to the hypogastric arteries in both the suprarenal (7 vs 17 mm; P = .009) and infrarenal (8 vs 24 mm; P < .0001) groups. No migration occurred in either group in patients with good iliac fixation. Multivariate logistic regression analysis revealed that iliac fixation, as evidenced by iliac fixation length (P = .004) and the device to hypogastric artery distance (P = .002), was a significant independent predictor of migration, whereas suprarenal or infrarenal treatment was not a significant predictor of migration. During a clinical follow-up period of 45 +/- 22 months (range, 12-70 months), there have been no aneurysm ruptures, abdominal aortic aneurysm-related deaths, or surgical conversions in either group.Distal iliac fixation is important in preventing migration of both suprarenal and infrarenal aortic endografts that have longitudinal columnar support. Secure iliac fixation minimizes the risk of migration despite suboptimal proximal aortic neck anatomy. Extension of both iliac limbs to cover the entire common iliac artery to the iliac bifurcation seems to prevent endograft migration.

View details for DOI 10.1016/j.jvs.2006.09.061

View details for Web of Science ID 000243987200006

View details for PubMedID 17263997

Abstract

Colonic ischemia after aortic reconstruction is a devastating complication with high mortality rates. This study evaluates whether Colon Mucosal Oxygen Saturation (CMOS) correlates with colon ischemia during aortic surgery.Aortic reconstruction was performed in 25 patients, using a spectrophotometer probe that was inserted in each patient's rectum before the surgical procedure. Continuous CMOS, buccal mucosal oxygen saturation, systemic mean arterial pressure, heart rate, pulse oximetry, and pivotal intra-operative events were collected.Endovascular aneurysm repair (EVAR) was performed in 20 and open repair in 5 patients with a mean age of 75 +/- 10 (+/-SE) years. CMOS reliably decreased in EVAR from a baseline of 56% +/- 8% to 26 +/- 17% (P < 0.0001) during infrarenal aortic balloon occlusion and femoral arterial sheath placement. CMOS similarly decreased during open repair from 56% +/- 9% to 15 +/- 19% (P < 0.0001) when the infrarenal aorta and iliac arteries were clamped. When aortic circulation was restored in both EVAR and open surgery, CMOS returned to baseline values 56.5 +/- 10% (P = 0.81). Mean recovery time in CMOS after an aortic intervention was 6.4 +/- 3.3 min. Simultaneous buccal mucosal oxygen saturation was stable (82% +/- 6%) during aortic manipulation but would fall significantly during active bleeding. There were no device related CMOS measurement complications.Intra-operative CMOS is a sensitive measure of colon ischemia where intraoperative events correlated well with changes in mucosal oxygen saturation. Transient changes demonstrate no problem. However, persistently low CMOS suggests colon ischemia, thus providing an opportunity to revascularize the inferior mesenteric artery or hypogastric arteries to prevent colon infarction.

View details for DOI 10.1016/j.jss.2006.05.014

View details for Web of Science ID 000242202300004

View details for PubMedID 16978651

Abstract

The appropriate size threshold for endovascular repair of small abdominal aortic aneurysms (AAA) is unclear. We studied the outcome of endovascular aneurysm repair (EVAR) as a function of preoperative aneurysm diameter to determine the relationship between aneurysm size and long-term outcome of endovascular repair.We reviewed the results of 923 patients treated in a prospective, multicenter clinical trial of EVAR. Small aneurysms were defined according to two size thresholds of 5.5 cm and 5.0 cm. Two-way analysis was used to compare patients with small aneurysms (<5.5 cm, n = 441) to patients with large aneurysms (> or =5.5 cm, n = 482). An ordered three-way analysis was used to compare patients with small AAA (<5.0 cm, n = 145), medium AAA (5.0 to 5.9 cm, n = 461), and large AAA (> or =6.0 cm, n = 317). The primary outcome measures of rupture, AAA-related death, surgical conversion, secondary intervention, and survival were compared using Kaplan-Meier estimates at 5 years.Median aneurysm size was 5.5 cm. The two-way comparison showed that 5 years after EVAR, patients with small aneurysms (<5.5 cm) had a lower AAA-related death rate (1% vs 6%, P = .006), a higher survival rate (69% vs 57%, P = .0002), and a lower secondary intervention rate (25% vs 32%, P = .03) than patients with large aneurysms (> or =5.5 cm). Three-way analysis revealed that patients with small AAAs (<5.0 cm) were younger (P < .0001) and were more likely to have a family history of aneurysm (P < .05), prior coronary intervention (P = .003), and peripheral occlusive disease (P = .008) than patients with larger AAAs. Patients with smaller AAAs also had more favorable aortic neck anatomy (P < .004). Patients with large AAAs were older (P < .0001), had higher operative risk (P = .01), and were more likely to have chronic obstructive pulmonary disease (P = .005), obesity (P = .03), and congestive heart failure (P = .004). At 5 years, patients with small AAAs had better outcomes, with 100% freedom from rupture vs 97% for medium AAAs and 93% for large AAAs (P = .02), 99% freedom from AAA-related death vs 97% for medium AAAs and 92% for large AAAs (P = .02) and 98% freedom from conversion vs 92% for medium AAAs and 89% for large AAAs (P = .01). Survival was significantly improved in small (69%) and medium AAAs (68%) compared to large AAAs (51%, P < .0001). Multivariate Cox proportional hazards modeling revealed that aneurysm size was a significant independent predictor of rupture (P = .04; hazard ratio [HR], 2.195), AAA-related death (P = .03; HR, 2.007), surgical conversion (P = .007; HR, 1.827), and survival (P = .001; HR, 1.351). There were no significant differences in secondary intervention, endoleak, or migration rates between small, medium, and large AAAs.Preoperative aneurysm size is an important determinant of long-term outcome following endovascular repair. Patients with small AAAs (<5.0 cm) are more favorable candidates for EVAR and have the best long-term outcomes, with 99% freedom from AAA death at 5 years. Patients with large AAAs (> or =6.0 cm) have shorter life expectancy and have a higher risk of rupture, surgical conversion, and aneurysm-related death following EVAR compared to patients with smaller aneurysms. Nonetheless, 92% of patients with large AAAs are protected from AAA-related death at 5 years. Patients with AAAs of intermediate size (5 to 6 cm) represent most of the patients treated with EVAR and have a 97% freedom from AAA-related death at 5 years.

View details for DOI 10.1016/j.jvs.2006.06.048

View details for Web of Science ID 000241714300002

View details for PubMedID 17098519

Abstract

To test the hypothesis that a level of chemical and electrical stimulation exists that allows differentiation of progenitor cells into organized contracting myocytes.A custom-made bioreactor with the capability of delivering electrical pulses of varying field strengths, widths, and frequencies was constructed. Individual chambers of the bioreactor allowed continuous electrical stimulation of cultured cells under microscopic observation. On day 0, 1% dimethylsulfoxide (DMSO), known to differentiate cells into myocytes, was added to P19 progenitor cells. Additionally, for the next 22 days, electrical pulses of varying field strengths (0-3 V/cm), widths (2-40 ms), and frequencies (10-25 Hz) were continuously applied. On day 5, the medium containing DMSO was exchanged with regular medium, and the electrical stimulation was continued. From days 6-22, the cells were visually assessed for signs of viability, contractility, and organization.P19 cells remained viable with pulsed electrical fields <3 V/cm, pulse widths <40 ms, and pulse frequencies from 10 to 25 Hz. On day 12, the first spontaneous contractions were observed. For individual colonies, local synchronization and organization occurred; multiple colonies were synchronized with externally applied electrical fields.P19 progenitor cells progress to organized contracting myocytes after chemical and electrical stimulation. Incorporation of such cells into existing methods of producing endothelial cells, fibroblasts, and scaffolds may allow production of improved tissue-engineered vascular grafts.

View details for Web of Science ID 000238334300015

View details for PubMedID 16784327

Abstract

Secure proximal fixation of endografts to the infrarenal aortic neck is known to be important in the short- and long-term success of endovascular aneurysm repair. We sought to determine the relative importance of distal iliac fixation in preventing endograft migration and adverse clinical events after endovascular aneurysm repair.We reviewed the outcome of 173 patients treated from 1996 to 2003 at Stanford University Medical Center with an externally supported stent graft. Quantitative image analysis of the postimplantation computed tomography scan was performed to determine the proximal aortic and distal iliac fixation lengths and the proximity the distal end of the stent graft to the iliac bifurcation. Subsequent follow-up computed tomography scans were reviewed for evidence of stent graft migration. Patients were grouped according to good (>15 mm), intermediate, or bad (<10 mm) aortic fixation and good (iliac fixation length > or =25 mm and iliac limbs <10 mm from iliac bifurcation), intermediate, or bad (<25-mm fixation length) iliac fixation.Stent graft migration of 10 mm or more was seen in 17 patients (10%) during the 23 +/- 19-month follow-up period. Patients with no migration had a greater iliac fixation length (30 +/- 12 mm) than those with migration (22 +/- 8 mm; P = .01), and the distal ends of the iliac limbs were closer to the iliac bifurcation (15 +/- 12 mm) than in patients with migration (25 +/- 10 mm; P < .001). Patients with no migration also had a greater proximal aortic fixation length (23 +/- 12 mm) than migration patients (13 +/- 7 mm; P = .001). There were no migrations among patients with good iliac fixation whether aortic fixation was good, intermediate, or bad (0/63; 0%). Among patients with bad/intermediate iliac and good aortic fixation, there were 5 (9%) of 58 patients had migrations. Patients with both bad/intermediate iliac and bad/intermediate aortic fixation had the highest migration rate (12/52; 23%). Cox proportional hazards regression modeling revealed that the significant factors predicting migration were poor proximity of the distal end of the iliac limbs to the iliac bifurcation (odds ratio 17.2; P = .01) and aortic fixation length (odds ratio 2.0; p = 0.007 for each centimeter). Iliac extender modules were placed in 9 patients with bad iliac fixation and migration, with no further migration during a mean follow-up of 12 months. Patients with good iliac and aortic fixation and no endoleak on the initial postprocedure computed tomography scan (n = 43) had no migrations, secondary procedures, or adverse clinical events over a 2-year follow-up period.Iliac fixation, along with proximal aortic fixation, is an important factor in preventing the migration of stent grafts that have longitudinal columnar support. Patients with good iliac fixation did not experience migration even in the presence of suboptimal proximal aortic fixation. Close proximity of the distal end of the stent graft to the iliac bifurcation seems to provide stability against migration.

View details for DOI 10.1016/j.jvs.2006.01.031

View details for Web of Science ID 000238046700012

View details for PubMedID 16765227

Abstract

Currently available vascular grafts have been limited by variable patency rates, material availability, and immunological rejection. The creation of a tissue-engineered vascular graft (TEVG) from autologous stem cells would potentially overcome these limitations. As a first step in creating a completely autologous TEVG, our objective was to develop a novel system for culturing undifferentiated mouse embryonic stem cells (mESC) in a three-dimensional (3D) configuration and under physiological pulsatile flow and pressure conditions.A bioreactor was created to provide pulsatile conditions to a specially modified four-well Labtek Chamber-Slide culture system. Undifferentiated mESC were either suspended in a 3D Matrigel matrix or suspended only in cell-culture media within the culture system. Pulsatile conditions were applied to the suspended cells and visualized by video microscopy.Undifferentiated mESC were successfully embedded in a 3D Matrigel matrix and could withstand physiological pulsatile conditions. Video microscopy demonstrated that the mESC in the 3D matrix were constrained to the wells of the culture system, moved in unison with the applied flows, and were not washed downstream; this was in contrast to the mESC suspended in media alone.Undifferentiated mESC can be grown in 3D and under pulsatile conditions. We will use these results to study the effects of long-term pulsatile conditions on the differentiation of mESC into endothelial cells, smooth muscle cells, and fibroblast cells with the long-term goal of creating a completely autologous TEVG.

View details for DOI 10.1016/j.jss.2006.2.017

View details for Web of Science ID 000237337000005

View details for PubMedID 16542683

Abstract

Problems of displacement, poor healing, degradation of the polymers and corrosion of the metallic frame in endovascular devices still require in-depth investigations. As the tissues and the foreign materials are in close contact, it is of paramount importance to efficiently investigate the interfaces between them. Inclusion in polymethymethacrylate (PMMA) permits us to obtain thin slides and preserve the capacity to perform the appropriate stainings. An AneuRx prosthesis was harvested in bloc with the surrounding tissues at the autopsy of a patient 25 months post deployment in a 5.7 cm diameter AAA and sectioned in the direction of the blood flow in two halves. A cross-section of the encapsulated distal segment together with the surrounding aneuryshmal sac was embedded in polymethylmethacrylate (PMMA). Further to complete polymerization, slices of the specimen were cut on a precision banding saw under coolant. They were affixed onto methacrylate slides with a UV cured adhesive. Binding and polishing were done on a numeric grinder and slices 25 to 30 microm in thickness were stained with toluidine blue prior to observation in light microscopy. Additional slices were prepared for scanning electron microscopy and X-ray energy dispersive spectrometry for determination of the elemental composition of the Nitinol stent. The aortic wall did not demonstrate complete integrity along with its circumference. Some areas of rupture were noted. The content of the sac was heavily shrunk and was mostly acellular. The walls of the device were very well encapsulated. The PMMA embedding permitted the polyester wall, the Nitinol wire and the collagen to keep in close contact. Scanning electron microscopy involved backscattered electrons and confirmed the corrosion the Nitinol wire at the boundary with living tissues. Based upon the results obtained, we believe that PMMA embedding is the most appropriate method to process endovascular devices for histological and material investigation. Needless to say, that paraffin embedding would have not been feasible for such a big size specimen involving different materials.

View details for DOI 10.1080/10731190600684041

View details for Web of Science ID 000237717700006

View details for PubMedID 16809135

Abstract

Information that can be obtained by magnetic resonance imaging (MRI) of explanted endovascular devices must be validated as this method is non-destructive. Histology of such a device together with its encroached tissues can be elegantly performed after polymethymethacrylate (PMMA) embedding, but this approach requires destruction of the specimen. The issue is therefore to determine if the MRI is sufficient to fully validate an explanted device based upon the characterization of an explanted specimen. An AneuRx device deployed percutaneously 25 months earlier in a 75-year-old patient was removed en bloc at autopsy together with the surrounding aneurysmal sac and segments of the upstream and downstream arteries. Macroscopic pictures were taken and a slice of the cross-section was processed for histology after polymethylmethacrylate (PMMA) embedding. For the magnetic resonance imaging investigation, the device was inserted in a Biospec 4.7 T MRI system with a 20 mm diameter birdcage resonator used for both emission and reception. A Spin-Echo (SE) was used to acquire both T1 proton density (PD) and T2 weighted images. A gradient-echo (GE) sampling of a free induction decay (GESFID) was used to generate multiple GE images using a single excitation pulse so that four images at different TE were obtained in the same acquisition. The selected explanted device was outstandingly well-healed compared to most devices harvested from humans. No inflammatory process was observed in contact or at distance of the materials. In MRI T1 images display no specific contrast and were homogeneous in the different tissues. The contrast was improved on proton density weighed images. On the T2 weighed images, the different areas were well identified. The diffusion images displayed in the surrounding B region had the greatest diffusion coefficient and the greatest anisotropy. The MRI analysis of the explanted AneuRx device illustrates the possibilities of this technique to characterize the interaction of the endovascular graft with the surrounding tissues. MRI is a breakthrough to investigate explanted medical devices but it also can be advantageously used in vivo to obtain virtual biopsies, because real biopsies to determine the 3 Bs (biocompatibility, biofunctionality and bioresilience) cannot be carried out as they could obviously initiate infection and degradation of the foreign materials.

View details for DOI 10.1080/10731190600581825

View details for Web of Science ID 000235950000008

View details for PubMedID 16537177

Abstract

We sought to determine whether intermittent short-duration exposure to low wall shear stress could induce intimal thickening in arteries chronically exposed to high shear stress. An arteriovenous fistula (AVF) was created between the left common carotid artery and the corresponding external jugular vein in 20 Japanese white male rabbits. After 4 weeks, blood flow was increased 10-fold to 182 +/- 39 ml/min and shear stress was increased to 33.4 +/- 13 dyn/cm(2). The AVF was then occluded for 1 h by finger compression with an 85% reduction in carotid artery blood flow (27 +/- 7 ml/min) and a reduction in wall shear stress to 4.9 +/- 1.7 dyn/cm(2) (P < 0.0001). Release of finger compression restored flow to the AVF and high shear stress to the carotid artery. This procedure was repeated at weekly intervals with a cumulative total of 4 h of low shear stress exposure. Arteries exposed to intermittent low shear stress developed a layer of intimal thickening which consisted of 3-4 layers of smooth muscle cells lined with thin elastic fibers and medial hyperplasia. Control arteries exposed to 8 weeks of continuous high shear had no intimal thickening. Transient exposure to low shear stress upregulated TGF-beta1, MMP-2, -14, and TIMP-2 gene expression while MMP-9 expression was downregulated. We conclude that repeated, intermittent short-duration exposure to low shear stress in the setting of high flow and high shear stress can induce arterial intimal thickening. Short-duration alterations in hemodynamic forces can induce rapid vascular cell message expression, which may effect arterial remodeling. This experiment suggests that a threshold value of 5 dyn/cm(2) may be needed in order to initiate and sustain the intimal thickening response.

View details for DOI 10.1016/j.yexmp.2005.04.005

View details for Web of Science ID 000234620200004

View details for PubMedID 15961075

Abstract

Autologous brachiobasilic transposition arteriovenous fistulas (AVFs) are desirable but require long incisions and extensive surgical dissection. To minimize the extent of surgery, we developed a catheter-based technique that requires only keyhole incisions and local anesthesia.The technique involves exposure and division of the basilic vein at the elbow. A guidewire is introduced into the vein, and a 6F "push catheter" is advanced over the guidewire and attached to the vein with sutures. Gently pushing the catheter proximally inverts, or intussuscepts, the vein. Side branches that are felt as resistances when pushing the catheter forward are localized, clipped, and divided under direct vision. Throughout the procedure, the endothelium always remains intraluminal. The basilic vein is externalized at the axilla without dividing it proximally and is tunneled subcutaneously, where it is anastomosed to the brachial artery.Thirty-two patients underwent the procedure--31 as outpatients. The mean duration of operation was less than 90 minutes. All patients tolerated the procedure well, and 31 required only intravenous sedation and local anesthesia. At a mean follow-up of 8 months, the primary patency rate of AVFs in patients with basilic vein diameters of 4 mm or more on preoperative duplex ultrasonography was 80%, vs 50% for those with vein diameters less than 4 mm. Overall, 78% of patent AVFs were being successfully accessed and 22% were still maturing at last follow-up.Autologous brachiobasilic transposition AVFs can be created by using catheter-mediated techniques that facilitate the mobilization and tunneling of the basilic vein through small incisions. Medium-term data suggest that the inversion method results in acceptable maturation and functionality of AVFs created with this technique.

View details for DOI 10.1016/j.jvs.2005.07.013

View details for Web of Science ID 000233090000026

View details for PubMedID 16275452

Abstract

Delayed endograft metallic strut failures detected in vivo with multidetector row computed tomography (MDCT) are reported in two patients who underwent endovascular abdominal aortic aneurysm repair with AneuRx and Talent endografts. In both instances, nitinol fractures were associated with proximal migration and type I endoleak. In both cases, the metallic strut fractures were detected with transverse sections from 16-channel MDCT angiograms and confirmed by using volume rendering. These cases highlight the previously unreported ability of thin-section, high-resolution MDCT angiography to detect endograft strut fractures.

View details for DOI 10.1016/j.jvs.2005.07.009

View details for Web of Science ID 000233090000038

View details for PubMedID 16275461

Abstract

Angioplasty and stenting of short segment obstructions is highly effective in the treatment of aorto-iliac occlusive disease. However, long-segment, diffuse and calcific aorto-iliac atherosclerosis is most effectively treated with surgical bypass. While aorto-femoral bypass procedures are durable and effective, too often patients are elderly, high risk and poor candidates for open surgery. Endografting of the abdominal aorta and iliac arteries is aimed at improving the short and long-term results of endovascular treatment of extensive, end-stage aorto-iliac disease. Aorto-iliac endografts are widely used in the treatment of aneurysmal disease. Early experiences with endografts in the treatment of occlusive disease are promising. However, evidence that long-term patency of endografts will be substantially better than angioplasty and stenting is not yet available. Prospective clinical trials are needed to determine the role of endografts in the treatment strategy of aorto-iliac occlusive disease.

View details for Web of Science ID 000232879000004

View details for PubMedID 16160682

Abstract

To report successful endovascular repair of thoracic aortic aneurysms in 2 patients with human immunodeficiency virus (HIV).Thoracic and abdominal aortic aneurysms (AAA) were found in a 60-year-old woman 1 year after she was diagnosed with HIV. Because of pain and risk of rupture, the AAA was repaired with conventional open techniques in February 1997, while the thoracic aneurysm was excluded in a staged procedure using a homemade endograft delivered through a 10-mm conduit sewn to the aortic tube graft. Two months later, new aneurysms were found in the superficial femoral arteries bilaterally; both were excised and replaced with vein grafts. After 7 years, the patient is well and no longer takes antiretroviral medication. Surveillance imaging shows continued patency of the stent-graft without evidence of leak or migration. In a more contemporary case, a 46-year-old man was found to have 5 focal aneurysms in the aorta; the most proximal descending thoracic aneurysm increased 2 cm in 2 weeks. The two thoracic aneurysms were successfully excluded using 2 Excluder stent-grafts. At 7 months, he was doing well, and the aneurysm had shrunk 11 mm.Endovascular and open treatment of HIV-related aneurysms is possible, with excellent long-term results. Patients with long-life expectancy should be treated according to the same guidelines as patients without HIV.

View details for Web of Science ID 000229874600020

View details for PubMedID 15943519

Abstract

To examine the feasibility and clinical outcome of a novel, minimally invasive technique for harvesting the great saphenous vein (GSV) for use in peripheral arterial bypass surgery.Between May 2001 through March 2003, 27 patients (15 men; mean age 71+/-10 years) underwent extremity bypass procedures for limb salvage (88%) or disabling claudication (12%) using the inversion technique to harvest the GSV. The veins were turned "inside out" using a unique catheter and guidewire system. With the endothelial surface exposed, valve leaflets were excised, and adherent thrombus was washed away. Veins were inverted again to turn the endothelial surface back inside the lumen for use as a bypass conduit.Inversion vein harvesting and arterial bypass were completed in 24 (89%) of 27 patients; 2 patients were treated with synthetic grafts because of small GSVs. Another patient was found after vein harvesting to have inadequate arterial outflow despite a good quality conduit. The average vein length was 45+/-10 cm; a mean 4+/-1 incisions were made, including those for arterial exposure. Incisions made to divide vein tributaries averaged 2 cm in length. Duration of vein harvesting was 25 minutes (range 5-80). Wound complications were minor (2 hematomas, 2 cases of erythema, 2 seromas). Of 6 grafts that occluded after 30 days, 5 involved small-diameter vein grafts (< 3.5 mm). At a mean 12 months, primary and assisted primary graft patency rates were 88% (14/16) and 94% (15/ 16), respectively, for grafts with minimum diameters > or = 4 mm versus 38% (3/8) primary patency for veins < 4 mm (n = 8, p < 0.001). The limb salvage rate was 92% (22/24).Over-the-wire inversion saphenectomy is a simple and reliable minimally invasive technique for arterial bypass. Incisions are small and cosmetically superior to those of the traditional long incision method. One-year follow-up suggests that grafts harvested by inversion technique have excellent durability when the minimum vein diameter is > or = 4 mm, as determined by preoperative vein mapping.

View details for Web of Science ID 000229874600018

View details for PubMedID 15943517

Abstract

To determine the impact on late postoperative renal function of suprarenal and infrarenal fixation of endografts used to treat infrarenal abdominal aortic aneurysm (AAA).Retrospective analysis of 277 patients treated from 2000 to 2003 with three different endografts at two clinical centers. Five patients on dialysis for preoperative chronic renal failure were excluded. Group IF of 135 patients treated with an infrarenal device (Medtronic AneuRx) was compared with group SF of 137 patients treated with a suprarenal device (106 Cook Zenith and 31 Medtronic Talent). Renal function was evaluated by calculating preoperative and latest postoperative creatinine clearance (CrCl) using the Cockcroft formula. Patients who developed a >20% decrease in CrCl were considered to have significantly impaired renal function.There were no significant differences in patient age, sex, aneurysm size, preoperative risk factors, dose of intra- and postoperative contrast, or baseline CrCl (IF: 69.3 mL/min, SF: 71.7 mL/min, P = .4). Follow-up time of 12.2 months was the same in both groups. CrCl decreased significantly during the follow-up period in both groups (IF: 69.3 mL/min to 61.7 mL/min, P < .01; SF: 71.7 mL/min to 64.9 mL/min, P < .03). Postoperative CrCl (IF: 61.7 mL/min, SF: 64.9 mL/min, P = .3), and the rate of CrCl decrease during the follow-up period (IF: -10.9%, SF: -9.5%, P = .2) was not different between the two groups. The number of patients with a >20% decrease in CrCl was not different between the two groups (IF: n = 35 [25.9%], SF: n = 41 [29.9%], P = .46). However, the magnitude of decrease in CrCl in patients with renal impairment was greater in patients treated with suprarenal fixation endografts (SF: -39%) compared with those treated with infrarenal endografts (IF: -31%, P = .005). This greater degree of renal impairment was not due to identifiable differences in preoperative risk factors, age, or baseline CrCl. No patients in these series required dialysis.Regardless the type of endograft used, there is a 10% decrease in CrCl in the first year after endovascular aneurysm repair. Suprarenal fixation does not seem to increase the likelihood of postoperative renal impairment. Decline in renal function over time after endovascular aortic repair is probably due to multiple factors, and measures known to be effective in protecting kidneys should be considered for these patients. Long-term follow-up with measurement of CrCl, along with renal imaging and regular blood pressure measurements, should be performed to detect possible late renal dysfunction. Prospective studies comparing suprarenal versus infrarenal fixation are needed to confirm those results.

View details for Web of Science ID 000229622000002

View details for PubMedID 15944586

Abstract

To evaluate displacement and bending of the renal arteries during respiration.Seven men (mean age 59+/-7 years, range 54-71) were imaged with contrast-enhanced magnetic resonance angiography (MRA). Two phases of the MRA were acquired during separate normal inspiration and expiration breath-holds. Displacement of the kidneys and renal ostia and changes in renal branch angle were measured in both coronal and axial views. Arterial curvature and distances between inspiration and expiration renal artery centerlines were computed at 1-mm intervals for the first 2 cm of each branch.Significant kidney displacement was observed in both the coronal and axial views, with maximum displacement on the right side; the right kidney at expiration was 13.2+/-7 mm superior and 6.3+/-3.4 mm posterior of its position during inspiration. By comparison, the renal ostia were relatively fixed, displacing 10-fold less than the kidneys. This displacement differential resulted in significant renal branch angle changes between inspiration and expiration, with the branches being more perpendicular at expiration. Right and left branch angles were significantly different from each other in the axial view, with the right artery taking off more anteriorly. The renal artery centerlines were displaced approximately 2.5 mm at a distance of 1 cm from the ostia, with little displacement change in the second centimeter. The right renal artery was more curved than the left, with more respiratory-induced curvature change near the ostia.Positional change of the kidneys during respiration induces both bending and change in angulation of the renal arteries. This bending can have a complex 3-dimensional shape near the ostia. In the setting of renal artery stenting, this motion may adversely affect the artery and/or the stent, possibly contributing to restenosis.

View details for Web of Science ID 000229874600016

View details for PubMedID 15943515

Abstract

To compare the outcome of patients with small abdominal aortic aneurysms (AAA) treated in a prospective trial of endovascular aneurysm repair (EVAR) to patients randomized to the surveillance arm of the UK Small Aneurysm Trial.All patients with small AAA (< or = 5.5 cm diameter) treated with a stent graft (EVARsmall) in the multicenter AneuRx clinical trial from 1997 to 1999 were reviewed with follow up through 2003. A subgroup of patients (EVARmatch) who met the age (60-76 years) and aneurysm size (4.0-5.5 cm diameter) inclusion criteria of the UK Small Aneurysm Trial were compared to the published results of the surveillance patient cohort (UKsurveil) of the UK Small Aneurysm Trial (NEJM 346:1445, 2002). Endpoints of comparison were aneurysm rupture, fatal aneurysm rupture, operative mortality, aneurysm related death and overall mortality. The total patient years of follow-up for EVAR patients was 1369 years and for UK patients was 3048 years. Statistical comparisons of EVARmatch and UKsurveil patients were made for rates per 100 patient years of follow up (/100 years) to adjust for differences in follow-up time.The EVARsmall group of 478 patients comprised 40% of the total number of patients treated during the course of the AneuRx clinical trial. The EVARmatch group of 312 patients excluded 151 patients for age < 60 or > 76 years and 15 patients for AAA diameter < 4 cm. With the exception of age, there were no significant differences between EVARsmall and EVARmatch in pre-operative factors or post-operative outcomes. In comparison to the UKsurveil group of 527 patients, the EVARmatch group was slightly older (70 +/- 4 vs. 69 +/- 4 years, p = 0.009), had larger aneurysms (5.0 +/- 0.3 vs. 4.6 +/- 0.4 cm, p < 0.001), fewer women (7 vs. 18%, p < 0.001), and had a higher prevalence of diabetes and hypertension and a lower prevalence of smoking at baseline. Ruptures occurred in 1.6% of EVARmatch patients and 5.1% of UKsurveil patients; this difference was not significant when adjusted for the difference in length of follow up. Fatal aneurysm rupture rate, adjusted for follow up time, was four times higher in UKsurveil (0.8/100 patient years) than in EVARmatch (0.2/100 patient years, p < 0.001); this difference remained significant when adjusted for difference in gender mix. Elective operative mortality rate was significantly lower in EVARmatch (1.9%) than in UKsurveil (5.9%, p < 0.01). Aneurysm-related death rate was two times higher in UKsurveil (1.6/100 patient years) than in EVARmatch (0.8/100 patient years, p = 0.03). All-cause mortality rate was significantly higher in UKsurveil (8.3/100 patient years) than in EVARmatch (6.4/100 patient years, p = 0.02).It appears that endovascular repair of small abdominal aortic aneurysms (4.0-5.5 cm) significantly reduces the risk of fatal aneurysm rupture and aneurysm-related death and improves overall patient survival compared to an ultrasound surveillance strategy with selective open surgical repair.

View details for DOI 10.1016/j.ejvs.2005.03.003

View details for Web of Science ID 000228842700008

View details for PubMedID 15966088

Abstract

Migration of endovascular stent grafts has been related to the security of proximal device fixation to the aortic neck. This study evaluated the importance of iliac fixation in preventing longitudinal in vivo device displacement of a modular, externally supported stent graft.Experimental ovine infrarenal aneurysms (n = 8) were treated with a fully supported, modular, bifurcated stent graft (AneuRx, Medtronic, Santa Rosa, Calif). Minimum iliac fixation length (1 cm) was used in four animals and iliac extender modules were used to achieve maximum iliac fixation in four animals. Suture anastomosis of bifurcated polyester grafts to the infrarenal aorta served as controls (n = 8). Aortic grafts were displaced in vivo by applying downward traction to a guidewire that was passed over the iliac flow divider and brought out both femoral arteries. The displacement force needed to initiate stent-graft migration was recorded and compared with the force needed to disrupt the sutured anastomosis.There was no difference in animal weight (88.8 +/- 2.5 kg vs 87.5 +/- 2.9 kg), aortic neck diameter (12.7 +/- 0.9 mm vs 13.4 +/- 1.1 mm), aortic neck length (23.2 +/- 0.9 mm vs 21.8 +/- 2.4 mm), experimental aneurysm size (24.7 +/- 1.1 mm vs 24.2 +/- 2.0 mm), or iliac artery diameter (9.0 +/- 1.5 mm vs 9.3 +/- 0.5 mm) among the groups. Iliac fixation length was 31.0 +/- 0.3 mm in the maximum iliac fixation group and 11 +/- 0.25 mm in the minimum fixation group (P < .0001). Peak displacement force to initiate migration was 30.2 +/- 5.5 N (range, 25 to 38) in animals with maximum iliac fixation compared with 18.1 +/- 3.7 N (range, 13 to 21) in those with minimum fixation (P = .01). The force needed to disrupt the control surgical anastomosis was 40.6 +/- 7.5 N (range, 31 to 50) (P < .01).Maximizing iliac fixation length increases the longitudinal in vivo force needed to displace a fully supported stent graft by 67%. This suggests that increasing iliac fixation length may reduce the long-term risk of migration in patients undergoing endovascular aneurysm repair.

View details for DOI 10.1016/j.jvs.2004.12.050

View details for Web of Science ID 000228702200019

View details for PubMedID 15874932

Abstract

To report stent-graft repair of a traumatic aortic pseudoaneurysm in proximity to a celiacomesenteric trunk.An 18-year-old woman suffered a large gunshot wound to the right flank. At laparotomy, only a large, nonexpanding right retroperitoneal hematoma was found, which was thought to represent significant penetrating trauma to the kidney mass. The patient was monitored in the intensive care unit. One week later, computed tomography revealed a partially infarcted right kidney and a 2.3-cm supraceliac aortic pseudoaneurysm, with adjacent bullet fragments. An angiogram confirmed the pseudoaneurysm and showed it to be 7 mm from the celiacomesenteric trunk. Endovascular repair was undertaken with a 16 x 55-mm AneuRx stent-graft, which was successfully placed across the aortic pseudoaneurysm without covering the celiacomesenteric trunk. Imaging at 12 months revealed no endoleak and full pseudoaneurysm exclusion.This operative approach is appropriate for the individual patient who has suitable anatomy and a clinical course that requires immediate repair of an aortic injury to prevent further complications and delays in ancillary treatments.

View details for Web of Science ID 000226954100023

View details for PubMedID 15683266

Abstract

The past decade has seen the evolution of an exciting technology that has changed forever the treatment of aortic aneurysmal disease. From rather crude homemade stent-grafts constructed in the surgical suite to elegant commercially manufactured devices in a variety of configurations and sizes, the aortic endograft has experienced a meteoric rise in popularity to become a beneficial, minimally invasive therapy that can obviate the risk of rupture and death. There are now 3 approved endovascular devices on the market for infrarenal abdominal aortic aneurysm repair, and it is likely that additional and improved devices will become available in the future. This review revisits the developmental history of the aortic endograft, noting the ongoing refinements that have arisen from our experiences with the growing population of stent-graft patients. Although research continues to search for solutions to the problems of endoleak and migration, long-term results even with the earlier second and third-generation devices are better than has been achieved with open surgical repair.

View details for PubMedID 15760266

Abstract

The primary objective of the CaRESS Phase I trial is to determine the sample size needed to reliably test the hypothesis that carotid stenting systems with distal embolic protection (CAS) is equivalent to carotid endarterectomy (CEA) in the treatment of symptomatic and asymptomatic carotid artery disease in a broad-risk population. A total of 397 patients were treated at 14 clinical centers. The primary endpoint results of combined all-cause mortality and stroke at 30-days and 1-year are presented. The CaRESS Phase I study was able to closely resemble clinical practice and results suggest equivalence between treatment groups.

View details for PubMedID 16084444

Abstract

Endovascular repair has been used over a decade as a treatment of abdominal aortic aneurysm, and has become a widely accepted treatment method with a low rate of perioperative complications. Endoleak, perigraft blood flow outside endograft but within aneurysmsac, has been intensively studied during the last 10 years of endovascular aneurysm repair (EVR). The natural history of aneurysms with endoleak and the true clinical significance of various types of endoleaks remains unclear. Type I/III endoleak has been found to be associated with aneurysm rupture, while the risk of rupture of aneurysms with type II endoleak and endotension appears very small. In endotension, the aneurysm sac remains pressurized, even if there is no evidence of an endoleak. Currently,it is accepted that type I/III endoleaks should be corrected, preferably by endovascular means, due to the risk of rupture. If endovascular repair is not possible, then open conversion should be considered. The risk of conversion should be weighed against the risk of aneurysm rupture. Treatment of type II endoleaks and endotension is more controversial. In those with aneurysm enlargement,secondary interventions are often performed.

View details for DOI 10.1016/j.suc.2004.04.009

View details for Web of Science ID 000224296400009

View details for PubMedID 15364558

View details for DOI 10.1016/j.jvs.2004.07.016

View details for Web of Science ID 000227388200040

View details for PubMedID 15337899

View details for Web of Science ID 000223415300002

View details for PubMedID 15298517

Abstract

The primary objective of aneurysm repair is to prevent aneurysm rupture while avoiding aneurysm-related death. This manuscript reviews the primary and secondary outcome measures following endovascular aneurysm repair (EVAR) in relation to similar outcome measures for open surgical repair. Both EVAR and open repair are effective in preventing aneurysm rupture, although late ruptures can occur with either treatment method. The late risk of rupture following EVAR is less that 1% per year using current endovascular devices. Aneurysm-related death rate appears to be lower following EVAR compared to open surgery, primarily due to a lower perioperative mortality rate. Actuarial 5-year survival after both endovascular and open aneurysm repair is approximately 70%. Perioperative outcome measures favor EVAR over open repair for patients with suitable anatomy with reduced morbidity and more rapid patient recovery. Short and long-term outcomes following endovascular repair compare favorably to open repair. However, prospective studies are needed to better define the long-term outcomes using comparable endpoints.

View details for Web of Science ID 000224803000005

View details for PubMedID 15365514

Abstract

Artery wall motion and strain play important roles in vascular remodeling and may be important in the pathogenesis of vascular disease. In vivo observations of circumferentially nonuniform wall motion in the human aorta suggest that nonuniform strain may contribute to the localization of vascular pathology. A velocity-based method to investigate circumferential strain variations was previously developed and validated in vitro; the current study was undertaken to determine whether accurate displacement and strain fields can be calculated from velocity data acquired in vivo. Wall velocities in the porcine thoracic aorta were quantified with PC-MRI and an implanted coil and were then time-integrated to compute wall displacement trajectories and cyclic strain. Displacement trajectories were consistent with observed aortic wall motion and with the displacements of markers in the aortic wall. The mean difference between velocity-based and marker-based trajectory points was 0.1 mm, relative to an average pixel size of 0.4 mm. Propagation of error analyses based on the precision of the computed displacements were used to demonstrate that 10% strain results in a standard deviation of 3.6%. This study demonstrates that it is feasible to accurately quantify strain from low wall velocities in vivo and that the porcine thoracic aorta does not deform uniformly.

View details for DOI 10.1002/mrm.20137

View details for Web of Science ID 000223121400008

View details for PubMedID 15282810

Abstract

We reviewed the structural findings of explanted AneuRx stent grafts used to treat abdominal aortic aneurysms, and relate the findings to clinical outcome measures.We reviewed data for all bifurcated AneuRx stent grafts explanted at surgery or autopsy and returned to the manufacturer from the US clinical trial and worldwide experience of more than 33,000 implants from 1996 to 2003. Devices implanted for more than 1 month with structural analysis are included in this article. Explant results were analyzed in relation to cause of explantation and pre-explant evidence of endoleak, enlargement, or device migration.One hundred twenty explanted stent grafts, including 37 from the US clinical trial, were analyzed. Mean implant duration was 22 +/- 13 months (range, 1-61 months). Structural abnormalities included stent fatigue fractures, fabric abrasion holes, and suture breaks. The mean number of nitinol stent strut fractures per explanted device was 3 +/- 4, which represents less than 0.2% of the total number of stent struts in each device. The mean number of fabric holes per explanted device was 2 +/- 3, with a median hole size of 0.5 mm(2). Suture breaks were seen in most explanted devices, but composed less than 1.5% of the total number of sutures per device. "For cause" explants (n = 104) had a 10-month longer implant duration (P =.007) compared with "incidental" explants (n = 16). "For cause" explants had more fractures (3 +/- 5; P =.005) and fabric holes (2 +/- 3; P =.008) per device compared with "incidental" explants, but these differences were not significant (P =.3) when adjusted for duration of device implantation. Among clinical trial explants the number of fabric holes in grafts in patients with endoleak (2 +/- 3 per device) was no different from those without endoleak (3 +/- 4 per device; P = NS). The number of fatigue fractures or fabric holes was no different in grafts in clinical trial patients with pre-explant aneurysm enlargement compared with those without enlargement. Pre-explant stent-graft migration was associated with a greater number of stent strut fractures (5 +/- 7 per device; P =.04) and fabric holes (3 +/- 3 per bifurcation; P =.03) compared with explants without migration. Serial imaging studies revealed inadequate proximal, distal, or junctional device fixation as the probable cause of rupture or need for conversion to open surgery in 86% of "for cause" explants. Structural device abnormalities were usually remote from fixation sites, and no causal relationship between device findings and clinical outcome could be established.Nitinol stent fatigue fractures, fabric holes, and suture breaks found in explanted AneuRx stent grafts do not appear to be related to clinical outcome measures. Longer term studies are needed to confirm these observations.

View details for DOI 10.1016/j.jvs.2004.03.008

View details for Web of Science ID 000222522300001

View details for PubMedID 15218454

Abstract

To present the management of acute arterial ischemia following major abdominal and orthopedic surgery using a percutaneous thrombectomy device and a low dose of thrombolytic agent.A 38-year-old woman with T-8 paraplegia from a traumatic fall developed pelvic osteomyelitis, for which a left hemipelvectomy, hysterectomy, and partial vaginal resection were performed. Twelve hours after the procedure, the patient developed an ischemic left leg. Computed tomographic angiography demonstrated an occlusion of the left external iliac and common femoral arteries. A Turbo Trellis percutaneous thrombectomy device was used to lyse the left external iliac artery thrombosis using 1 mg of tissue plasminogen activator infused between the proximal and distal occluding balloons of the device. Total dispersion time was 5 minutes. There was complete thrombus removal without any significant bleeding complications. At 6 months, the artery remains widely patent.Combination therapy with mechanical thrombectomy devices and low dose thrombolytic agents can be used to treat acute arterial occlusions at a single setting. The increased speed of the Turbo Trellis may allow for smaller doses of thrombolytic agents and shorter treatment times.

View details for Web of Science ID 000222157100017

View details for PubMedID 15174917

Abstract

Late complications following endovascular aneurysm repair indicate the need for long-term surveillance. Clinical trials involving endoluminal stent grafts have typically used computed tomography angiography as the main imaging modality for surveillance. However, computed tomography angiography exposes the patient to higher levels of ionizing radiation, nephrotoxic agents, and increased cost compared to duplex ultrasound. Duplex ultrasound scanning has been widely used for surveillance of abdominal aortic aneurysms for many years. It is well established and the procedure of choice for noninvasive imaging of the aorta. It offers the advantages of easy access, decreased cost, no radiation exposure, and no nephrotoxicity. There is little controversy about duplex scanning for preoperative patient evaluation or surveillance of patients with small aneurysms. However, the use and reliability of duplex scanning in the evaluation and surveillance of patients following endovascular repair is controversial. This article will discuss the benefits, techniques, and limitation of duplex ultrasound in the long-term surveillance of endografts following endovascular abdominal aortic aneurysm repair.

View details for PubMedID 15185182

Abstract

The purpose of this study was to evaluate the effectiveness and demonstrate the advantages of a new technique for carotid angioplasty and stenting (CAS) with proximal cerebral protection through a direct transcervical approach, as compared with a percutaneous transfemoral approach.CAS procedures were carried out in 25 consecutive patients, 4 with the femoral approach and 21 through a 2-cm incision at the base of the neck, with the patient under local anesthesia. For transcervical occlusion and protective shunting (TOPS), a short 9F sheath was inserted directly into the common carotid artery and connected to a 6F sheath placed percutaneously in the ipsilateral internal jugular vein. After clamping the common carotid artery proximal to the 9F sheath, internal carotid artery blood flow reversal was confirmed or an occluding external carotid balloon was placed. A filter interposed between the arterial and venous sheaths collected embolic debris from transcarotid manipulations. The arterial puncture was directly repaired with suture. Neurologic status was assessed with the National Institutes of Health stroke scale by an independent neurology consultant before and after the procedure.One of the four percutaneous femoral approaches that failed because of tortuous anatomy was successfully treated with TOPS. Angiographic confirmation demonstrating resolution of asymptomatic (>80%; n = 12) stenosis or symptomatic (>60%; n = 12) stenosis was achieved in all patients with stents. A 0% technical failure rate and 0% combined 30-day stroke or mortality rate were achieved in all CAS attempted with TOPS. There were no hematomas in the cervical group, despite pretreatment with clopidogrel bisulfate and heparin, and one hematoma in the femoral group after failure of a Perclose arterial closure device. In one of the patients in the femoral group bilateral cholesterol emboli to the toes developed.TOPS solves problems of access, embolization into the cerebral and peripheral circulation, and specialized cerebral protection devices, and enables secure closure of the access vessel in patients given anticoagulation therapy. TOPS may provide a safer, more effective, economical means for performing CAS.

View details for DOI 10.1016/j.jvs.2004.01.045

View details for Web of Science ID 000221858500018

View details for PubMedID 15111851

Abstract

We investigated the effects of sequential and prolonged exposure to high and low wall shear stress on arterial remodeling using a rabbit arteriovenous fistula (AVF) model. Blood flow was increased by approximately 17-fold to 20-fold when the AVF was open, and returned to normal when the AVF was occluded. Repeated opening and closing of the AVF resulted in sequential exposure of the artery to high and low wall shear stress. High flow and high wall shear stress induced arterial dilatation, elongation, and tortuosity, without intimal thickening. The common carotid artery was elongated 37% after 4 weeks of high flow, and was shortened 10% after 6 weeks of normal flow. Subsequent cycles of high flow induced less elongation, with less shortening after return to normal flow. Enlargement of the distal segment was more dramatic than in the proximal segment, despite exposure to the same volume of flow and the same initial high wall shear stress after creation of the AVF. The distal carotid segment enlarged more than did the proximal segment during each exposure to high flow. In segments of carotid artery exposed to low wall shear stress (<5 dynes/cm(2)) intimal thickening developed. These changes were maximal in the distal carotid segment, just before the AVF. Each cycle of low wall shear stress induced intimal thickening accompanied by medial hyperplasia. Intimal thickening was inhibited during periods of high flow when wall shear stress was high. Three cycles of flow alteration induced three layers of intimal thickening in the distal arterial segment, two layers of intimal thickening in the middle segment, and one layer of intimal thickening in the proximal segment. Long-term exposure to low wall shear stress induced severe intimal thickening and medial hyperplasia in different segments. Thus the response of the carotid artery afferent to an AVF varies along the length of the artery, with maximum enlargement, elongation, and tortuosity in the distal segment, just proximal to the AVF. Similarly, intimal thickening in response to low wall shear stress is maximal in the distal carotid artery. It appears that intimal thickening is related to local levels of low wall shear stress, and occurs when wall shear stress chronically falls to less than 5 dynes/cm(2).

View details for DOI 10.1016/j.jvs.2003.10.058

View details for Web of Science ID 000227387100017

View details for PubMedID 14981455

Abstract

This preliminary study examined the technical efficacy, safety, and cost of treating arterial occlusions with a single device that combines pharmacologic and mechanical thrombolysis.The technical success, bleeding complications, and costs for the first 26 consecutive patients in whom lower extremity ischemia was treated with the Trellis infusion catheter (TIC) were analyzed. Procedure time, thrombolytic infusion time, technical success, bleeding complications (major and intracranial hemorrhage), interventional suite time, and 30-day amputation-free survival were evaluated.15 of 26 patients (58%) who received treatment with the TIC had acute arterial occlusions, and 11 of 26 patients (42%) had nonacute arterial occlusions. Nineteen of 26 patients (73.1%) received treatment of an infrainguinal occlusion, and 7 of 26 patients (26.9%) received treatment of a suprainguinal occlusion. Lower extremity native arteries were treated in 18 of 26 patients (69%), and lower extremity bypass grafts in 8 of 26 patients (31%). The technical success rate with TIC treatment was 92%, and the 30-day amputation-free survival rate was 96%. There was no difference in technical success or amputation-free survival rate between acute versus nonacute arterial occlusions, native artery versus bypass grafts, and suprainguinal versus infrainguinal arterial occlusions. Procedure time was 2.1 +/- 0.9 hours, and infusion time was 0.3 +/- 0.2 hours. There were no bleeding complications; however, 3 of 26 patients (11.5%) required further intervention to treat distal embolization. The overall mean cost for patients with TIC treatment was $3216 +/- $1740.Early results of TIC treatment in patients with arterial occlusions suggest that it is as effective as traditional catheter-directed thrombolysis. Furthermore, there were no bleeding complications, likely the result of TIC requiring shorter procedure and infusion times.

View details for DOI 10.1016/j.jvs.2003.10.061

View details for Web of Science ID 000227387100010

View details for PubMedID 14981448

Abstract

This study was carried out to compare the functional outcomes after hypogastric artery bypass and coil embolization for management of common iliac artery aneurysms in the endovascular repair of aortoiliac aneurysms (EVAR).Between 1996 and 2002, 265 patients underwent elective or emergent EVAR. Data were retrospectively reviewed for 21 (8%) patients with iliac artery aneurysms 25 mm or larger that involved the iliac bifurcation. Patients underwent hypogastric artery bypass (n = 9) or coil embolization (n = 12). Interviews about past and current levels of activity were conducted. A disability score (DS) was quantitatively graded on a discrete scale ranging from 0 to 10, corresponding to "virtually bed-bound" to exercise tolerance "greater than a mile." Worsening or improvement of symptoms was expressed as a difference in DS between two time points (-, worsening; +, improvement).There was no difference in age (72.6 +/- 7.3 years vs 73.1 +/- 6.4 years), sex (male-female ratio, 8:1 vs 11:1), abdominal aortic aneurysm size (60.1 +/- 5.9 mm vs 59.3 +/- 7.0 mm), or number of preoperative comorbid conditions (1.9 +/- 0.8 vs 2.1 +/- 0.8) between hypogastric bypass and coil embolization groups, respectively. Mean follow-up was shorter after hypogastric bypass (14.8 vs 20.5 months; P <.05). There was no difference in the mean overall baseline DS between the bypass and the embolization groups (8.0 vs 7.8). Six (50%) of the 12 patients with coil embolization reported symptoms of buttock claudication ipsilateral to the occluded hypogastric artery. No symptoms of buttock claudication were reported after hypogastric bypass (P <.05). There was a decrease in the DS after both procedures; however, coil embolization was associated with a significantly worse DS compared with hypogastric artery bypass (4.5 vs 7.3; P <.001). In 4 (67%) of 6 patients with claudication after coil embolization symptoms improved, with a DS of 5.4 at last follow-up. This was significantly worse than in patients undergoing hypogastric artery bypass, with a DS of 7.8 at last follow-up (P <.001). There was no difference between the groups in duration of procedure, blood loss, length of hospital stay, morbidity, or mortality (0%).Hypogastric artery bypass to preserve pelvic circulation is safe, and significantly decreases the risk for buttock claudication. Preservation of pelvic circulation results in significant improvement in the ambulatory status of patients with common iliac artery aneurysms, compared with coil embolization.

View details for DOI 10.1016/j.jvs.2003.07.012

View details for Web of Science ID 000188535000036

View details for PubMedID 14743144

Abstract

To determine how many patients with abdominal aortic aneurysms (AAA) meet the anatomical selection criteria for AneuRx stent-graft repair in community hospitals of Northern California.The records were reviewed of 220 AAA patients (171 men, 49 women) who were considered for endovascular repair by the treating vascular surgeon at 28 community hospitals in Northern California between January and October 2001. Contrast computed tomographic angiography (CTA) and selective arteriography were performed at each institution and reviewed by a centralized, independent image-reading center. Selection criteria determined by the manufacturer and published in the indications for use were applied to each set of imaging studies. The number of patients who met inclusion criteria were recorded, as were the anatomical characteristics of each aneurysm.The mean aneurysm size in the 220 patients was 55.3 +/- 0.7 mm. Among these patients, 122 (55%) were judged to be candidates for endovascular repair and 98 (45%) were considered ineligible. The primary anatomical reason for ineligibility was a short infrarenal neck in 43 (44%) patients, followed by a large proximal neck diameter (25, 25%), iliac aneurysms (10, 10%), extremely tortuous or calcified neck (7, 7%), iliac occlusion (6, 6%), and small distal aortic bifurcation and accessory renal arteries (5, 5%). Four (4%) patients were classified as non-candidates due to poor quality imaging. There was no difference in aneurysm diameter (54.0 +/- 0.8 versus 57.1 +/- 1.2 mm, p=NS) or age (72.2 +/- 1.2 versus 74.6 +/- 2.2 years, p=NS) between candidates and non-candidates. However, proportionally more men (60%) than women (39%) were eligible for endovascular repair with the AneuRx stent-graft (p<0.05). All 122 patients who were considered candidates for endovascular repair were treated, with successful stent-graft placement achieved in 121 (99%).Fifty-five percent of patients considered for endovascular AAA repair in community hospitals in Northern California met the anatomical selection criteria for the AneuRx stent-graft. Men appeared to be twice as likely to meet the eligibility requirements as women. Unfavorable infrarenal neck anatomy was the primary exclusion criterion for endovascular repair in this community setting.

View details for Web of Science ID 000188851400004

View details for PubMedID 14748631

Abstract

The purpose of this study was to determine the incidence and significance of aneurysm enlargement, with or without treatment, in relation to the primary end points of rupture, surgical conversion, aneurysm-related death, and survival following endovascular repair.Aneurysm (AAA) size changes and clinical outcome of all patients treated from 1997 through 1998 during the Phase II AneuRx multicenter clinical trial of endovascular AAA repair were reviewed. Aneurysm dimensions and the presence or absence of endoleak were determined by an independent core laboratory, with enlargement or shrinkage defined as a diameter change of 5 mm or more compared with baseline.Among 383 patients (89% men, 11% women, age 73 +/- 9 years), with a mean device implant time of 36 +/- 11 months (median = 39 months), aneurysm diameter decreased from 5.7 +/- 1.0 at baseline to 5.2 +/- 1.0 at 3 years (P =.0001). A total of 46 patients (12%) experienced AAA enlargement, 199 patients (52%) had no change in AAA diameter, and 138 patients (36%) had a decrease in AAA diameter of 5 mm or more. Significant risk factors for enlargement included age (enlargement patients were 4 years older on average than patients with aneurysms that decreased in size; P =.002) and the presence of an endoleak (P <.001). Among patients with endoleak at any time, 17% had aneurysm enlargement, whereas only 2% of patients without endoleak had aneurysm enlargement (P <.001). Patients with enlargement were more likely to undergo secondary endovascular procedures and surgical conversions (P <.001). Twenty patients (43%) with enlargement underwent treatment, and 26 patients were untreated. There were two deaths following elective surgical conversion and one death in a patient with untreated enlargement and a type I endoleak. Three aneurysms ruptured: one with enlargement, one with no change, and one with a decrease in aneurysm size; all three aneurysms were larger than 6.5 cm. Kaplan-Meier analysis showed that freedom from rupture at 3 years was 98% with enlargement, 99% with no change, and 99% with decrease in AAA size (log-rank test, not significant). Freedom from AAA death at 3 years was 93% in patients with enlargement, 99% in no increase, and 99% in decrease (P =.005). Survival at 3 years was 86% with increase, 82% with no change, and 93% with decrease (P =.02).Aneurysm enlargement following endovascular repair was not associated with an increased risk of aneurysm rupture or decrease in patient survival during a 3-year observation period. Aneurysm size rather than enlargement may be a more meaningful predictor of rupture. Close follow-up and a high re-intervention rate (43%) may account for the low risk of rupture in patients with enlargement. The long-term significance of aneurysm enlargement following endovascular repair remains to be determined.

View details for DOI 10.1016/j.jvs.2003.08.002

View details for Web of Science ID 000187840600026

View details for PubMedID 14718827

Abstract

We reviewed the incidence of stent-graft migration after endovascular aneurysm repair in a prospective multicenter trial and identified factors that may predispose to such migration.All patients who received treatment during the course of the multicenter AneuRx clinical trial were reviewed for evidence of stent-graft migration over 5 years, from 1996 to 2001. Post-deployment distance from the renal arteries to the proximal end of the stent graft and the proximal fixation length (length of the infrarenal neck covered by the stent graft) were determined in patients for whom pre-procedure and post-procedure computed tomography scans were measured in an independent core laboratory.Stent-graft migration was reported in 94 of 1119 patients, with mean time after device implantation of 30 +/- 11 months. Freedom from migration was 98.6% at 1 year, 93.4% at 2 years, and 81.2% at 3 years (Kaplan-Meier method). Subset (n = 387) analysis revealed that initial device deployment was lower in 47 patients with migration, as evidenced by a greater renal artery to stent-graft distance (1.1 +/- 0.7 cm), compared with 340 patients without migration (0.8 +/- 0.6 cm; P =.006) on post-implantation computed tomography scan. Proximal fixation length was shorter in patients with migration (1.6 +/- 1.4 cm) compared with patients without migration (2.3 +/- 1.4 cm; P =.005). There was significant variation in migration rate among clinical sites (P <.001), ranging from 0% to 30% (median, 8%), with a greater than twofold difference in migration rate between the lowest quartile (6%) and the highest quartile (15%) clinical sites. Univariate and multivariate analysis revealed that renal artery to stent-graft distance (P =.001) and proximal fixation length (P =.005) were significant predictors of migration, and that each millimeter increase in distance below the renal arteries increased risk for subsequent migration by 5.8% and each millimeter increase in proximal fixation length decreased risk for migration by 2.5%. Pre-implantation aortic neck length, neck diameter, degree of device oversizing, correct versus incorrect oversizing, device type (stiff vs flexible), placement of proximal extender cuffs at the original procedure, and post-procedure endoleak were not significant predictors of migration. Migration was treated with placement of extender modules in 23 patients and surgical conversion in 7 patients; 64 patients (68%) with migration have required no treatment.Stent-graft migration among patients treated in the AneuRx clinical trial appears to be largely related to low initial deployment of the device, below the renal arteries, and short proximal fixation length. Significant variation in migration rate among clinical sites highlights the importance of the technical aspects of stent-graft deployment. Advances in intraoperative imaging and deployment techniques that have been made since completion of the clinical trial facilitate precision of device placement below the renal arteries and should increase proximal fixation length. Whether this, together with increased iliac fixation length, will result in lower risk for migration remains to be determined in long-term follow-up studies.

View details for DOI 10.1016/S0741-5214(03)00946-7

View details for Web of Science ID 000186955400028

View details for PubMedID 14681625

Abstract

Endothelial cell activation and proliferation are the essential steps in flow-induced arterial remodeling. We investigated endothelial cell turnover in the early stages of high-flow in the rabbit common carotid arteries using an arteriovenous fistula (AVF) model by kinetic investigation of cell proliferation and cell molecular analysis. BrdU was administrated to label endothelial cells (ECs) in DNA synthetic phase (S-phase) of the cell mitotic cycle. Pulse labeling revealed that ECs entered S-phase at 1.5 days of AVF (0.93 +/- 0.19%). Endothelial cell labeling index (EC-LI) peaked at 2 days of AVF (8.90 +/- 0.87%) with a high index of endothelial cell mitosis (EC-MI, 1.67 +/- 0.47%). Endothelial cell density increased remarkably at 3 days of AVF with a significant decrease in EC-LI (54%) and EC-MI (60%). Study of kinetics of EC proliferation revealed that endothelial cells took 16-24 h to finish one cycle of cell mitosis. Tracking investigation of pulse BrdU-labeled endothelial cells at 1.5 days showed that more than 66% of endothelial cells were BrdU-labeled 1.5 days after labeling. VEGF, integrin alphanubeta3, PECAM-1, and VE-cadherin were upregulated significantly preceding endothelial cell proliferation and kept at high levels during endothelial cell proliferation. These data suggest that endothelial cell proliferation is the initial step in flow-induced arterial remodeling. Hemodynamic forces may drive endothelial cell downstream migration. Expression of VEGF and cell junction molecules contribute to flow-induced arterial remodeling.

View details for DOI 10.1016/S0014-4800(03)00032-7

View details for Web of Science ID 000184052500001

View details for PubMedID 12834620

Abstract

To report successful combined percutaneous mechanical thrombectomy and pharmacological lysis for axillosubclavian vein thrombosis, with rapid clot removal at a single setting using low-dose thrombolysis.Two consecutive patients presented with arm swelling; the diagnosis of axillosubclavian vein thrombosis was confirmed with duplex ultrasound. Both patients were treated percutaneously with the Solera mechanical thrombectomy device, after which 5 mg of tissue plasminogen activator were delivered within approximately 10 minutes via the Trellis infusion catheter to remove any residual thrombus. Completion venography and serial duplex ultrasound scans in follow-up demonstrated widely patent axillosubclavian veins with no residual thrombus in both cases.Standard treatment of axillosubclavian vein thrombosis may require 12 to 36 hours, with multiple trips to the angiography suite. The novel technique combining mechanical thrombectomy and pharmacological lysis can be performed safely and successfully at a single setting with a small dose of the lytic drug.

View details for Web of Science ID 000186217600008

View details for PubMedID 14533970

View details for PubMedID 12832978

Abstract

Small infrarenal abdominal aortic aneurysms have a more favorable clinical and morphologic outcome compared with medium and large abdominal aortic aneurysms following endovascular aneurysm repair(EVAR).A prospective clinical series of 206 patients undergoing elective EVAR between 1996 and 2001.A tertiary care academic health center.Patients were grouped according to aneurysm size: small (<50 mm), medium (50-60 mm), and large (>60 mm).Primary EVAR and secondary procedures to secure fixation of the stent graft and surgical conversions.Aneurysm diameter, endoleaks, and long-term morphologic changes were analyzed postoperatively with 3-dimensional reconstructions of computed tomographic angiograms.Groups were similar in age, comorbidities, and follow-up (mean +/- SD, 32.1 +/- 11.8 months). There were 30 small aneurysms, 92 medium aneurysms, and 84 large aneurysms, with a mean size of 45.1 +/- 3.7 mm, 53.8 +/- 3.1 mm, and 66.1 +/- 6.8 mm, respectively (P<.01). There was no significant difference in proximal neck or iliac artery diameter among the 3 groups. The proximal aortic neck length (28.1 +/- 11.6 mm [small]; 23.9 +/- 11.3 mm [medium]; and 22.1 +/- 11.6 mm [large]; P<.05) was significantly shorter in large aneurysms. Furthermore, there was a significant increase (6% [small]; 15% [medium]; and 21% [large]; P<.05) in angulated necks in large aneurysms. Following treatment, aneurysm diameter remained stable in most patients (83% [small]; 82% [medium]; and 83% [large]), with a mean decrease of 2.0 +/- 6.5 mm, 2.1 +/- 6.1 mm, and 3.7 +/- 7.7 mm in each group, respectively (P =.45). There was no difference in the incidence of endoleaks, aneurysm contraction, or aneurysm expansion based on preoperative aneurysm diameter. Secondary procedures were performed in 5 (20%) of 25, 9 (5.2%) of 170, and 5 (36%) of 11 aneurysms that contracted, remained stable, or expanded, respectively, following EVAR (P<.05).There is a 15% increase in neck angulation and a 27% decrease in neck length in large compared with small infrarenal abdominal aortic aneurysms, with no difference in outcome. Aneurysms that are stable following EVAR have a significantly lower incidence of requiring secondary procedures.

View details for Web of Science ID 000183366300022

View details for PubMedID 12799337

Abstract

A total of 1193 patients with infrarenal abdominal aortic aneurysms were treated with the AneuRx Stent Graft System at 19 US investigational centers from 1996 to 1999. This report summarizes clinical data collected and analyzed as of August 28, 2002. There have been 10 late (>30 days) aneurysm ruptures, 8 late (>30 days) aneurysm-related deaths, and 38 late (>30 days) surgical conversions, including 8 for rupture. Kaplan-Meier analyses of the primary outcome measures at 4 years indicate the following: a freedom from rupture rate of 98.4%; a freedom from surgical conversion rate of 90.4%; a freedom from aneurysm-related death rate of 96.9%; and a probability of survival rate, based on all-cause mortality, of 62.4%. Secondary outcome measures at 4 years include stent graft patency in 96.4%, endoleak in 13.9%, aneurysm enlargement in 11.5% and stent graft migration in 9.5% of patients. These results provide evidence that the AneuRx Stent Graft System continues to be a safe and effective treatment option for appropriately selected patients with infrarenal abdominal aneurysms.

View details for DOI 10.1067/mva.2003.311

View details for Web of Science ID 000182054400034

View details for PubMedID 12664000

Abstract

The goals of this laboratory model were to evaluate the performance of the surgical team and endolaparoscopic techniques in the porcine model of infrarenal abdominal aortic repair.Twenty-four pigs underwent full endolaparoscopic aorto-aortic graft implantation with voice-activated computerized robotics. The first group of 10 pigs (acute) was sacrificed while under anesthesia at 0.5 hours (5 animals) and 2 hours (5 animals). The second group of 14 pigs (survival) were recovered from anesthesia and maintained for 7 hours (5 pigs) and 7 days (9 pigs) prior to sacrifice. Survival animals were observed for evidence of hind limb dysfunction. All grafts were visually inspected at autopsy.All animals survived the operation. All grafts were successfully implanted, and all were patent with intact anastomoses at autopsy. Mean aortic clamp time for each group was as follows: acute, 92.9 +/- 28.04 minutes; survival, 59.6 +/- 13.8 minutes; P=0.0008. Total operative time for each group was as follows: acute, 179 +/- 39.6 minutes; survival, 164.6 +/- 48 minutes; P=0.44 ns. Estimated blood loss for each group was as follows: acute, 214 -/+ 437.8 mL; survival 169.2 +/- 271 mL; P=0.76 ns. from respiratory arrest; 1 animal suffered motor sensory dysfunction of the hind limbs (spinal cord ischemia); significant bleeding occurred in 6 of 24 pigs; 8 of the 9 seven-day survivors required minimal pain medication and had normal hind limb function.The reduction in aortic clamp time, total operative time, and blood loss as the study progressed indicate the feasibility of this surgical protocol and the maturation of the learning process, which is paramount in prevention of 2 main sources of morbidity: bleeding and spinal cord ischemia. The reduction in aortic clamp time between the acute and survival groups was dramatic and statistically significant. An intensive formal training program combining dry and live surgical laboratories is deemed essential for the development of endoscopic skill sets necessary for this challenging procedure.

View details for PubMedID 12856843

Abstract

To compare early and late functional outcomes, as well as survival and recovery, following endovascular or open repair of abdominal aortic aneurysm (AAA).Between 1996 and 2000, 294 patients underwent AAA repair (141 open and 153 endovascular); 57 patients from each group had 12-month follow-up for functional outcome assessment. Recovery was measured as hospital length of stay, skilled nursing requirement, and hospital readmission within 1 year to determine cumulative hospital utilization. Early (<6 months) functional outcomes were measured by activity level and convalescence days following surgery. Late (>6 months) functional outcomes were measured as ambulation, independent living, and employment status pre- and postoperatively.Operative mortality for open repair was 5 (3.5%) compared to 1 (0.6%) after an endovascular procedure (p<0.05). The endovascular group had a shorter hospital stay (2.8+/-2.8 versus 8.3+/-4.5 days) and fewer skilled nursing requirements (0% versus 26%; p<0.001). Cumulative hospital utilization over 12 months was 3.8 days for endovascular patients and 13.8 days for open repair (p<0.001). Recovery time was 99.3+/-84.1 days (range 14-365) in conventionally treated patients and 32.1+/-43.5 days (range 7-180) in the stent-graft group (p<0.001). At 6 months, 43 (75%) open and 54 (95%) endovascular patients had full recovery (p<0.01). Activity levels decreased in 13 (23%) open and 3 (5%) endovascular patients after surgery (p<0.01). There were no differences in ambulation, independent living, or employment status before and after treatment.Periprocedural survival following aneurysm repair is improved with endovascular grafting compared to open surgery, and recovery is more rapid, with a 78% reduction in total hospital days. Early functional outcomes are markedly improved with endovascular repair, while there is no difference in late functional outcomes between the procedures.

View details for Web of Science ID 000183272900002

View details for PubMedID 12751922

Abstract

Endovascular grafting of abdominal aortic aneurysms should be offered only to those patients with suitable anatomy. This is especially true at the level of the proximal aortic neck in order to secure long-term proximal fixation. Aortoiliac anatomy is easy to understand conceptually, however, it is difficult to define and measure quantitatively. In this article, we discuss the use of three dimensional computed tomographic angiography to determine aneurysm morphology and select patients for endovascular repair. Specifically, we apply our methods to define and measure angulation of the aorta and iliac arteries. The anatomic definition of the angulation of the proximal aortic neck is emphasized.

View details for Web of Science ID 000181692400010

View details for PubMedID 12658882

Abstract

The purpose of this study was to determine whether intrasac spectral Doppler flow velocities can predict whether or not a type II endoleak will spontaneously seal and to relate intrasac flow to preoperative branch vessel anatomy.Between October 1996 and June 2002, 265 patients with abdominal aortic aneurysms underwent endovascular repair. Patients with less than 24 months of follow-up and type I endoleaks were excluded. Type II endoleaks were confirmed with duplex scan and computed tomographic angiography. Two groups were identified: 14 patients with sealed endoleaks (<6 months) without intervention and 16 patients with persistent endoleaks greater than 6 months and without resolution. Spectral Doppler flow velocities were recorded from endoleaks within the aneurysm sac.The two groups were similar in age, demographics, and aneurysm morphology. The mean follow-up times were 29.9 +/- 7.9 months for sealed endoleaks and 30.2 +/- 8.6 months for persistent endoleaks (P = not significant). Spectral Doppler velocities were significantly lower in patients with sealed endoleaks compared with persistent endoleaks (75.5 +/- 78.8 cm/s versus 138.2 +/- 36.2 cm/s; P <.01). Patients with sealed endoleaks and low (<100 cm/s) intrasac Doppler velocities had significantly fewer patent inferior mesenteric arteries (43% versus 81%; P <.01), a smaller inferior mesenteric artery (5.6 +/- 1.8 mm versus 7.2 +/- 1.3 mm; P <.01), and fewer paired lumbar arteries (1.3 +/- 0.8 versus 2.4 +/- 0.6; P <.0001) compared with those with persistent endoleaks and high (>100 cm/s) intrasac flow velocities. Three patients with sealed endoleaks had Doppler velocities of 200 cm/s or greater. However, the diameter of the inferior mesenteric artery in these patients was 4 mm or less with no visualized lumbar arteries before surgery. Aneurysm diameter(-4.6 +/- 5.6 mm) and volume (-0.9 +/- 45.2 mL) decreased in patients with sealed endoleaks. Aneurysm diameter (1.8 +/- 4.9 mm) and volume (18.5 +/- 33.9 mL) increased slightly in patients with persistent endoleaks (P <.05). No ruptures or conversions occurred in any patient. Secondary interventions to treat type II endoleaks were unsuccessful in six of 16 patients (38%) with persistent endoleaks.Intrasac Doppler velocities can be used to predict whether a type II endoleak will spontaneously seal. High-velocity type II endoleaks are related to preoperative large branch vessel diameter and number and are resistant to endovascular treatment.

View details for DOI 10.1067/mva.2003.55

View details for Web of Science ID 000180465200002

View details for PubMedID 12514572

Abstract

Endothelial cells are stable and quiet in normal animals. They arrange regularly and have a smooth lumen surface and thin endothelial wall. According to Thoma's principle (1893) and Kamiya and Togawa's principle (1980) on the relationship of the vascular diameter to flow alteration, blood flow is in equilibrium to the diameter and in a physiological state. That is to say, there is no fast flow or slow flow. To understand the nature of the endothelial cells, we should investigate endothelial cells under flow alteration to break the equilibrium state. Endothelial cells under increased flow were studied in arteries with an arteriovenous fistula or in the capillaries of myocardium with volume-overloaded hearts or of the skeletal muscle by electrical stimulation. Those under decreased flow were studied by the closure of the fistula or by ceasing the stimulation. Endothelial cells in the coarctation of the arteries were also observed. Endothelial cells were activated by increased flow in the arteries and capillaries, while they were inactivated by decreased flow. Endothelial activation is characterized as lumen protrusions, increase of cytoplasmic organelles, abluminal protrusions, basement membrane degradation, internal elastic lamina degradation in the arteries, and sproutings in the capillaries. These are ultrastructurally comparable to angiogenesis. Endothelial inactivation is characterized by the decrease of endothelial cell number with apoptosis, which is ultrastructurally comparable to angioregression. We assume that endothelial cells respond to increased flow by angiogenesis and to decreased flow by angioregression.

View details for DOI 10.1002/jemt.10237

View details for Web of Science ID 000180088600002

View details for PubMedID 12500255

Abstract

To compare systemic complications between standard surgery and endovascular repair of abdominal aortic aneurysms (AAA) for both primary and late secondary procedures.At a single center between July 1993 and May 2000, 297 patients (255 men; mean age 73.4 +/- 8.1 years, range 50-93) were treated with open surgical repair; beginning in 1996, 200 (166 men; mean age 73.6 +/- 8.0 years, range 45-96) patients were treated with the AneuRx stent-graft. In a comparison of the cohorts, which were similar in terms of age, gender, and aneurysm diameter, the main outcomes were early major systemic morbidity following the primary procedure to treat the aneurysm and late (>30 days) organ system morbidity for any secondary procedures.Mean length of follow-up for open patients was 20.1 +/- 17.1 months (range 1-150) compared to 12.4 +/- 9.6 months (range 1-60) after endovascular repair (p<0.05). There were 36 (12.1%) systemic complications after the primary open surgery and 15 (7.5%) after endovascular repair (p=NS). There were 43 (14.5%) combined primary and secondary morbidities in the open surgery group versus 15 (7.5%) for patients undergoing endovascular repair (p<0.01). The need for invasive procedures to treat these primary and secondary systemic complications was 4 times greater in the open group (17, 5.7%) than in endograft patients (3, 1.5%) (p<0.05). After secondary procedures (32 in the open group and 30 in the endovascular patients) for graft-related complications, there were 7 (21.9%) adverse events in the open group versus none (0%) for endograft patients (p<0.01). Hospital lengths of stay following both primary and secondary procedures were lower for the endograft patients (p<0.01 and p<0.001, respectively).Endovascular stent-graft repair compared to open surgery has reduced the early and late morbidity by half. Complications that require invasive or secondary surgical procedures and hospitalization are reduced with endovascular repair.

View details for Web of Science ID 000181102400001

View details for PubMedID 12546569

Abstract

Elevated awake resting heart rate (HR) has been shown to be a major risk factor for cardiovascular disease. Since coronary ischaemic events appear to peak during transition from sleep to awake HR, we sought to determine whether the degree of diurnal HR fluctuation (dHRV) is an independent predictor of coronary and peripheral atherogenesis. In this study, we varied both baseline HR and dHRV using sino-atrial node ablation (SNA) in a primate model of diet-induced atherogenesis and determined the degree of plaque formation relative to both HR parameters.HR was recorded continuously for 6 months by an implantable intraaortic sensor/transmitter in 17 active unrestricted male cynomolgus monkeys. In nine monkeys, SNA was employed to create a wide spectrum of dHRV, and the power amplitude of dHRV was determined for the daily HRV cycle with power spectral analysis. After a 6-month diet induction period, percent coronary and carotid stenosis, intimal thickness and area were quantitated in each animal.Total serum cholesterol and mean HR were no different between high ( n= 10) and low ( n= 7) dHRV groups (866 mg% vs. 740 mg%, P> 0.2 and 130 +/- 22 and 115 +/- 13, P> 0.1, respectively). Percent carotid stenosis was markedly greater in both high HR and dHRV animals ([HR], 54 +/- 19 vs. 35 +/- 10, P< 0.04) and ([dHRV], 54 +/- 17 vs. 32 +/- 10, P< 0.01). Significant increases in all measures of coronary atherogenesis were found in high dHRV animals when compared with those with low dHRV (percent stenosis: 48% +/- 22 vs. 23% +/- 16, P< 0.02), (lesion area: 1.2 +/- 0.8 vs. 0.3 +/- 0.3, P< 0.02), and (intimal thickness: 0.3 +/- 0.1 vs. 0.1 +/- 0.1, P< 0.01), respectively. While there was a trend towards greater coronary atherogenesis in animals with high HR, this did not reach statistical significance.Elevated HR and dHRV are both associated with enhanced experimental atherosclerotic plaque formation. However, a greater degree of carotid and coronary atherogenesis is observed in animals with high dHRV. These findings suggest that elevated dHRV is a stronger predictor for susceptibility to atherogenesis than elevated HR alone. Such a relationship may be attributed to the potential role of dHRV in modulating the frequency of adverse near wall haemodynamic forces, which have been shown to induce atherosclerotic plaques. Lowering of dHRV in humans by exercise or pharmacological agents may have a beneficial role in retarding atherosclerotic plaque induction, progression and complication.

View details for DOI 10.1097/01.hjr.0000049240.55385.1e

View details for Web of Science ID 000180187300006

View details for PubMedID 12478202

Abstract

The purpose of this study was to quantify the degree of aortoiliac tortuosity and determine the relationship between aortoiliac angulation and the need for a secondary procedure following endovascular repair.Among 206 patients treated with the AneuRx stent graft, 3-year follow up data were available in 71 patients. Twenty eight patients without duplex and CT angiograms (CT angiography) on follow-up were excluded. The anatomy of the preoperative proximal aortic neck was evaluated using 3D-CT angiography reconstructed images in: a) Group I: 15 patients who required secondary procedures and b) Group II: 18 patients without any endovascular leak during follow up. The groups did not differ in age (72.9+/-6.1 versus 73.3+/-9.1) or aneurysm diameter (60.1+/-9.1 versus 60.5+/-10.1). In order to determine the aortoiliac tortuosity, we measured: a) the suprarenal aorta-infrarenal aortic neck angle: angle of the aorta at the level of the renal arteries, b) infrarenal aortic neck-aneurysm angle: angle of the aorta at the start of aneurysm, c) right iliac angle, d) left iliac angle, e) aortic neck length, f) aortic neck diameter.Computer-based measurements on 3D-CT angiography reconstructed images were: a) suprarenal aorta-infrarenal aortic neck angle: group I: (22.6+/-16.2), group II: (11.9+/-6.9), p<0.05; b) infrarenal aortic neck-aneurysm angle: group I: 17.6+/-12.4, group II: 18.8+/-9.4, p=NS; c) right iliac angle: group I: 22.9+/-12.6, group II: 20.4+/-9.5, p=NS; d) left iliac angle: group I: 22.4+/-10.5, group II: 19.1+/-12.2, p=NS; e) aortic neck length: group I: 18.9+/-5.3 mm, group II: 20.4+/-5.3 mm, p=NS; f) aortic neck diameter: group I: 24.1+/-1.0 mm, group II: 23.3+/-1.6, p=NS.Aortoiliac angulation can be defined and quantified. In patients requiring secondary procedures, there is an increased angulation at the proximal aortic neck angle.

View details for Web of Science ID 000181635900008

View details for PubMedID 12518115

Abstract

The response of endothelial cells to altered flow conditions has been studied extensively. However, the indirect effects of shear stress on medial smooth muscle cells (SMCs) have been less well characterized and a murine model of high shear stress has not been available.The hemodynamic changes that occur in a mouse aorta proximal to an aortocaval fistula (ACF) were characterized by measuring blood flow, aortic diameter, and calculating wall shear stress. This model was next used to evaluate cellular activation by assessing beta-galactosidase expression in fos-lacZ transgenic mice. Aortic specimens were examined by a chemiluminescent beta-galactosidase assay, cross-sectional histology, and Hautchen prep en face histology.Immediately after ACF construction, aortic diameter remained unchanged and wall shear stress increased 2.6-fold (49.57 +/- 5.89 to 134.93 +/- 15.69 dyn/cm(2), P < 0.05). Flow-induced aortic enlargement occurred gradually (0.61 +/- 0.03 to 1.18 +/- 0.05 mm at 21 days, P < 0.5) such that by 21 days after ACF, wall shear stress had returned to baseline (56.97 +/- 8.62 dyn/cm(2), P = ns compared to control). Aortas from fos-lacZ mice demonstrated increased beta-gal activity at 6 h and up to 7 days after ACF (1.81 +/- 0.22 rlu/microg in controls vs 41.41 +/- 16.28 rlu/microg at 6 h and 15.17 +/- 1.1 rlu/microg at 7 days, P < 0.5) On histologic evaluation, there was a significant increase in medial SMC staining that was most prominent in cells near the intima (2 +/- 0.3% positive cells in controls vs 67 +/- 10% at 6 h and 11 +/- 7.6 at 7 days, P < 0.5). Endothelial cells, evaluated by en face methods, did not demonstrate significant amounts of beta-gal positivity at the times studied.These in vivo findings using a new high shear stress model suggest that early and sustained activation of medial SMCs is a critical component of flow-induced enlargement. Further evaluation of these events may provide important insights into the mechanisms of pathologic arterial remodeling.

View details for DOI 10.1006/jsre.2002.6530

View details for Web of Science ID 000179528000016

View details for PubMedID 12443723

Abstract

This study investigated the effects of high flow and shear stress on the expression of matrix metalloproteinases (MMPs) and tissue inhibitor of metalloproteinase-2 (TIMP-2) during flow-induced arterial enlargement using a model of arteriovenous fistula (AVF) creation on the carotid artery with the corresponding jugular vein in Japanese white male rabbits. Flow increased 8-fold 7 days after AVF. Endothelial cells (EC) and smooth muscle cells (SMC) proliferated with internal elastic lamina (IEL) degradation in response to high flow and shear stress. Expression of MMP-2 mRNA peaked at 2 days (1700-fold) and maintained high level expression. MMP-9 mRNA gave a 10.8-fold increase within 2 days and decreased later. Their proteins were detected in EC and SMC. Membrane type-1-MMP (MT1-MMP) mRNA increased 121-fold at 3 days and maintained high expression. TGF-beta1 was increased after AVF. Two-peak up-regulation of Egr-1 mRNA was recognized at 1 and 5 days of AVF. These results suggest that high flow and shear stress can mediate EC and SMC to express MMP-2 and MMP-9, which degrade cell basement membranes and IEL to induce arterial enlargement. The disproportional increase in MT1-MMP and TIMP-2 might contribute to MMP-2 activation. Egr-1 and TGF-beta1 might play important roles in this process.

View details for DOI 10.1006/exmp.2002.2457

View details for Web of Science ID 000178016700009

View details for PubMedID 12231217

Abstract

In vivo quantification of vessel wall cyclic strain has important applications in physiology and disease research and the design of intravascular devices. We describe a method to calculate vessel wall strain from cine PC-MRI velocity data. Forward-backward time integration is used to calculate displacement fields from the velocities, and cyclic Green-Lagrange strain is computed in segments defined by the displacements. The method was validated using a combination of in vitro cine PC-MRI and marker tracking studies. Phantom experiments demonstrated that wall displacements and strain could be calculated accurately from PC-MRI velocity data, with a mean displacement difference of 0.20 +/- 0.16 mm (pixel size 0.39 mm) and a mean strain difference of 0.01 (strain extent 0.20). A propagation of error analysis defined the relationship between the standard deviations in displacements and strain based on original segment length and strain magnitude. Based on the measured displacement standard deviation, strain standard deviations were calculated to be 0.015 (validation segment length) and 0.045 (typical segment length). To verify the feasibility of using this method in vivo, cyclic strain was calculated in the thoracic aorta of a normal human subject. Results demonstrated nonuniform deformation and circumferential variation in cyclic strain, with a peak average strain of 0.08 +/- 0.11.

View details for DOI 10.1114/1.1513566

View details for Web of Science ID 000179121200005

View details for PubMedID 12449764

Abstract

The purpose of this study was to assess the time course of tropoelastin gene expression in the poststenotic dilatation segment of rabbit aorta with experimental coarctation.Midthoracic aortic coarctation was created in rabbits to produce a PSD. The time points of the study after coarctation were 1, 3, and 7 days and 2, 4, and 8 weeks (n = 3 each). Additional animals (n = 6) were subjected to hypercholesterolemia for analysis of tropoelastin expression in intimal lesions. Northern and Western blot analyses were used to quantitate tropoelastin messenger RNA (mRNA) and protein, and immunohistochemistry was used to analyze tropoelastin distribution.Thoracic aortic coarctation produced a moderate stenosis, which resulted in PSD. mRNA levels in the PSD segment decreased at days 1 and 3, followed by an increase at 2 and 4 weeks (P <.05 versus controls). This biphasic change in tropoelastin mRNA was associated with increase in tropoelastin protein levels at 2 and 4 weeks (P <.05 versus controls). PSD diameter reached a maximum at 4 weeks and did not increase significantly thereafter. The number of medial elastic laminae in PSD was reduced slightly, but media thickness was unchanged. Intimal lesions were much smaller in the PSD segment than in the proximal segment in animals with hypertension superimposed with hypercholesterolemia. Moreover, tropoelastin protein distributed not only in the intima but also in the media of the PSD.Tropoelastin gene expression is regulated in a biphasic pattern and precedes PSD formation. The differential distribution of tropoelastin in the media suggests a role for tropoelastin in the poststenotic adaptation response, which may provide increased elasticity to the PSD wall.

View details for DOI 10.1067/mva.2002.125017

View details for Web of Science ID 000178099600041

View details for PubMedID 12218987

Abstract

The purpose of this study was to define changes in aneurysm volume after endovascular repair of abdominal aortic aneurysm.A total of 154 consecutive patients who underwent endovascular repair of abdominal aortic aneurysm with the Medtronic AneuRx stent graft at Stanford University Hospital were evaluated. During a mean follow-up period of 15.8 +/- 11.3 months, serial computerized measurements of aneurysm volume and orthogonal maximal diameter were performed on helical computed tomographic scan data sets and maximal transverse diameter was measured manually from transverse computed tomographic images. Aortoiliac length (renal to hypogastric artery origin) was measured along the median luminal centerline and along the straight line.Aneurysm volume increased immediately after endovascular repair (from 180.2 +/- 69.9 mL to 187.9 +/- 71.6 mL; P <.001), but orthogonal and transverse diameter and aortoiliac length did not change significantly. During the follow-up period, mean volume decreased to 171.9 +/- 70.2 mL (P <.05) and straight-line and centerline aortoiliac length remained unchanged from preoperative values. Overall, volume decreased at a rate of 1.7 +/- 5.9 mL/mo (P <.001). During periods without endoleak, the rate of decrease was 3.2 +/- 5.5 mL/mo (P <.001), and during periods with endoleak, aneurysm volume increased at a rate of 2.0 +/- 5.3 mL/mo (P <.005), without a difference between types of endoleak. Predictive values for the presence of endoleak were similar for transverse and orthogonal diameter and volume. Logistic regression analysis showed volume to be most closely associated with the presence of endoleak.Aneurysm volume increases immediately after endovascular repair. After repair, aneurysm volume gradually decreases and aortoiliac length remains unchanged. Changes in volume parallel changes in maximal aneurysm diameter, and their association with the presence of an endoleak does not appear to be appreciably stronger.

View details for DOI 10.1067/mva.2002.126085

View details for Web of Science ID 000177489000016

View details for PubMedID 12170211

Abstract

The purpose of this study was to utilize an objective endpoint analysis of aneurysm treatment, which is based on the primary objective of aneurysm repair, and to apply it to a consecutive series of patients undergoing open and endovascular repair.Aneurysm-related death was defined as any death that occurred within 30 days of primary aneurysm treatment (open or endovascular), within 30 days of a secondary aneurysm or graft-related treatment, or any death related to the aneurysm or graft at any time following treatment. We reviewed 417 consecutive patients undergoing elective infrarenal aortic aneurysm repair: 243 patients with open repair and 174 patients with endovascular repair.There was no difference between the groups (open vs endovascular) with regard to mean age +/- standard deviation (73 +/- 8 years vs 74 +/- 8 years) or aneurysm size (64 +/- 2 mm vs 58 +/- 10 mm) (P = not significant [NS]). The 30-day mortality for the primary procedure after open repair was 3.7% (9/243) and after endovascular repair was 0.6% (1/174, P <.05). The 30-day mortality for secondary procedures after open repair was 14% (6/41) compared to 0% after endovascular repair (P <.05). The aneurysm-related death rate was 4.1% (10/243) after open surgery and 0.6% (1/174) after endovascular repair (P <.05). Mean follow-up was 5 months longer following open repair (P <.05). Secondary procedures were performed in 41 patients following open surgery and 27 patients following endovascular repair (P = NS). Secondary procedures following open repair were performed for anastomotic aneurysms (n = 18), graft infection (n = 6), aortoenteric fistula (n = 5), anastomotic hemorrhage (n = 4), lower extremity amputation (n = 4), graft thrombosis (n = 3), and distal revascularization (n = 1). Secondary procedures following endovascular repair consisted of proximal extender cuffs (n = 11), distal extender cuffs (n = 11), limb thrombosis (n = 3), and surgical conversion (n = 2). The magnitude of secondary procedures following open repair was greater with longer operative time 292 +/- 89 minutes vs 129 +/- 33 minutes (P <.0001), longer length of stay 13 +/- 10 days vs 2 +/- 2 days (P <.0001) and greater blood loss 3382 +/- 4278 mL vs 851 +/- 114 mL (P <.0001).The aneurysm-related death rate combines early and late deaths and should be used as the primary outcome measure to objectively compare the results of open and endovascular repair in the treatment of infrarenal abdominal aortic aneurysms. In our experience, endovascular aneurysm repair reduced the overall aneurysm-related death rate when compared to open repair. Secondary procedures are required after both open and endovascular repair. However, the magnitude, morbidity, and mortality of secondary procedures are reduced significantly with endovascular repair.

View details for DOI 10.1067/mva.2002.126314

View details for Web of Science ID 000177489000015

View details for PubMedID 12170210

Abstract

The purpose of this study was to determine the outcome of endovascular aneurysm repair in a defined geographic region during the first 2 years after Food and Drug Administration approval of a new endovascular device.Clinical results of all attempted endovascular aneurysm repairs from 1999 to 2001 with the AneuRx stent graft in the northern California/Nevada region were reviewed. All cases performed in 23 hospitals by 21 endovascular treatment teams were included on an intent-to-treat basis. Community physician training, proctoring, and assistance in case selection was provided by the manufacturer, with outcome monitored by external physician observers and clinical vascular specialists. Results in 22 community hospitals were compared with concurrent results in the regional university hospital training center and with results from the controlled, multicenter AneuRx clinical trial.Endovascular aneurysm repair was attempted in 257 patients by 20 endovascular teams working in 22 community hospitals. The mean number of cases per team was 13 +/- 2 (range, 1 to 36). Patient age was 74.1 +/- 6.5 years (89% men and 11% women), and 29% of patients were not candidates for open surgical repair because of multiple medical comorbidities. Mean aneurysm diameter was 5.7 +/- 0.8 cm. The endoluminal stent graft was successfully deployed in 254 patients (98.8%). In two patients, iliac access could not be obtained, and in one case, the iliac limb was misdeployed and the patient underwent successful open surgical repair. The surgical conversion rate was two of 257 patients (0.8%). The 30-day mortality rate was 1.2%, with one patient dying of stroke, one of multisystem organ failure, and one of cerebral hemorrhage. No device-related deaths occurred. Secondary procedures were performed in 8% of patients. Primary graft patency rate was 98%, and secondary graft patency rate was 100%. Concurrent university training center experience with 100 patients with similar characteristics and aneurysm size was not statistically different (deployment success rate, 100%; 30-day mortality rate, 0%; surgical conversion rate, 0%; secondary procedure rate, 8%). No aneurysm ruptures and no late surgical conversions have been seen in either the community or university experience, with follow-up periods extending to 2 years.Early results of endovascular aneurysm repair introduced into community practice are favorable. Initial community experience, with clinical support from the manufacturer, does not appear to differ significantly from concurrent results in the university training center or from results reported from the multicenter controlled clinical trial with the same device.

View details for DOI 10.1067/mva.2002.125795

View details for Web of Science ID 000177489000004

View details for PubMedID 12170201

Abstract

Cell proliferation and apoptosis are both involved in arterial wall remodeling. Increase in blood flow induces arterial enlargement. The molecular basis of flow-induced remodeling in large elastic arteries is largely unknown.An aortocaval fistula (ACF) model in rats was used to induce enlargement in the abdominal aorta. Aortic gene expression of transforming growth factors beta (TGF-beta) and apoptosis-related factors was assessed at 1 and 3 days and 1, 2, 4, and 8 weeks. Expression levels were determined using a ribonuclease protection assay and western blotting. Cell proliferation and apoptosis were analyzed using BrdU incorporation and TUNEL techniques.Blood flow increased 5-fold immediately after ACF (P<0.05). Lumen diameter of the aorta was 30% and 75% larger at 2 and 8 weeks respectively than those of controls (P<0.05). mRNA levels of TGF-beta1 and TGF-beta3 increased after ACF, peaked at 3 days (P<0.05) and returned to normal level at 1 week and thereafter. Western blotting showed enhanced expression of TGF-beta1 at 3 days and TGF-beta3 at 1 and 3 days and 1 week (P<0.05). mRNA levels of Bcl-xS initially decreased at 1 day, 3 days and 1 week, followed a return to baseline level at 2 weeks. Cell proliferation was observed at all time points after ACF (P<0.001 vs. controls) with proliferation in endothelial cells more significant than smooth muscle cells. Apoptosis was not significant.Gene expression of TGF-beta1 and beta3 precedes arterial enlargement. Expression of apoptosis related factors is little regulated in the early stage of the flow-induced arterial remodeling.

View details for PubMedID 12150715

Abstract

Duplex ultrasound scan (DUS) criteria for grading >50% carotid artery stenosis is typically divided into broad categories such as 50-79% stenosis, 80-99% stenosis, and occlusion. The purpose of this study is to validate DUS criteria for stratifying 50 to 100% carotid stenosis into 10% intervals using digital substraction cerebral angiography (DSCA) as the standard of comparison. Between 1996 and 2001, 163 patients were evaluated with duplex ultrasound and angiography. A total of 326 carotid arteries were studied using DUS in an accredited ICAVL vascular laboratory. Threshold velocity criteria for determining the degree of carotid stenosis was defined according to seven categories: <50%, 50-59%, 60-69%, 70-79%, 80-89%, 90-99%, and occlusion. Treatment decisions were based on the angiographic findings. In cases where the degree of stenosis as defined by duplex velocity criteria did not correlate with angiographically defined stenosis, each record was reviewed to determine whether the angiographic findings altered the surgeon's treatment decision. The sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) for DUS-defined degree of stenosis as compared to angiographically defined stenosis were determined. There was a high correlation (R = 0.96) between duplex scan and angiography in 93% (302/326) of the cases. Clinical management was altered in only 3% (10/326) of the cases because of the results of angiography. The DUS velocity criteria to grade the severity of carotid disease in 10% intervals is reliable and accurate. Clinical management of patients with carotid stenosis can be based solely on carotid DUS in 97% of patients considered for treatment of carotid artery disease.

View details for DOI 10.1007/s10016-001-0175-8

View details for Web of Science ID 000177802500003

View details for PubMedID 12118345

Abstract

To determine whether increasing experience with endovascular abdominal aortic aneurysm (AAA) repair in a single institution will result in improved outcome.A retrospective review was undertaken of 150 consecutive cases of endovascular AAA repairs performed using the AneuRx device between October 1996 and April 2000 in a university-based medical center. The population was divided into early and late groups of 75 patients each. Endpoints included technical success; complications; early (< or =30-day) morbidity, mortality and rupture; endoleak at discharge and at 1 month; early secondary intervention; proximal neck and iliac tortuosity; extender cuff placement; femoral reconstructions beyond primary repair; total fluoroscopy time; and contrast load.Baseline patient and aneurysm characteristics were similar between the 2 groups. Technical success was 98.7%; 2 cases were converted intraprocedurally owing to difficult iliac access (early group) and a severely angulated proximal neck (late group). There was a tendency toward more frequent use of intraoperative proximal extender cuffs in the early group (12% versus 4% in the late group, p=0.13). Femoral reconstructions were more frequent in the early group (36% versus 19%, p<0.025). While total contrast volume was similar (111 +/- 56 versus 105 +/- 45 mL, p=NS), total fluoroscopy time was significantly reduced (p<0.05) between the early and late groups.With attention to detail and careful patient selection, successful endovascular AAA repair can be achieved with very few conversions and low perioperative mortality even during the center's early experience. Evidence indicates, however, that a learning curve definitely exists, as shown by fewer access site problems, more accurate device deployments, and decreased fluoroscopy times as proficiency is attained.

View details for Web of Science ID 000176993800003

View details for PubMedID 12096939

Abstract

In planning operations for patients with cardiovascular disease, vascular surgeons rely on their training, past experiences with patients with similar conditions, and diagnostic imaging data. However, variability in patient anatomy and physiology makes it difficult to quantitatively predict the surgical outcome for a specific patient a priori. We have developed a simulation-based medical planning system that utilizes three-dimensional finite-element analysis methods and patient-specific anatomic and physiologic information to predict changes in blood flow resulting from surgical bypass procedures. In order to apply these computational methods, they must be validated against direct experimental measurements. In this study, we compared in vivo flow measurements obtained using magnetic resonance imaging techniques to calculated flow values predicted using our analysis methods in thoraco-thoraco aortic bypass procedures in eight pigs. Predicted average flow rates and flow rate waveforms were compared for two locations. The predicted and measured waveforms had similar shapes and amplitudes, while flow distribution predictions were within 10.6% of the experimental data. The average absolute difference in the bypass-to-inlet blood flow ratio was 5.4 +/- 2.8%. For the aorta-to-inlet blood flow ratio, the average absolute difference was 6.0 +/- 3.3%.

View details for DOI 10.1114/1.1496086

View details for Web of Science ID 000177640900001

View details for PubMedID 12220075

Abstract

To compare the outcomes of open versus endovascular repair of abdominal aortic aneurysm (AAA) in a cohort of patients who fulfill morphological criteria for endovascular repair.A retrospective review of 229 consecutive AAA patients treated over a 3-year period identified 149 patients who were candidates for endovascular repair based on preoperative computed tomography and angiography. Of the 149 patients, 79 (68 men; mean age 74 +/- 8 years) underwent endovascular repair with the AneuRx stent-graft; the remaining 70 (56 men; mean age 72 +/- 8 years) had open repair. Short-term outcome measures were 30-day mortality and procedure-related morbidity, length of stay in the intensive care unit and hospital, intraoperative blood loss, interval to oral diet, and time to ambulation. Long-term outcome measures included death and secondary procedures.There was no difference in the 30-day mortality between endovascular repair (2, 2.5%) and open repair (2, 2.9%), even though endovascular patients had more comorbidities (p<0.05). Overall length of stay was reduced for endovascular patients (3.9 +/- 2.4 days versus 7.7 +/- 3.1 days for surgical patients, p<0.0001). Fewer endograft patients had complications (24% versus 40% for open repair, p<0.05), and the severity of these complications was less, as evidenced by the shorter hospital stays for endovascular patients with complications compared to conventionally treated patients with complications (6.7 +/- 2.4 days versus 22.5 +/- 35.2 days, p<0.05). There were no aneurysm ruptures or late surgical conversions in either group.Patients with AAA who were endograft candidates but who were treated with open repair experienced more morbidity and had more complications than patients treated with stent-grafts. Despite increased comorbidities in the endograft patients, there was no increase in mortality compared to open repair. Both treatments required secondary procedures and appeared to be equally effective in preventing aneurysm rupture up to 3 years.

View details for Web of Science ID 000176993800001

View details for PubMedID 12096937

View details for DOI 10.1067/mva.2002.123991

View details for Web of Science ID 000175919100048

View details for PubMedID 12021728

View details for DOI 10.1067/mva.2002.123763

View details for Web of Science ID 000175919100047

View details for PubMedID 12021727

Abstract

Endoleaks and endotension are critically important complications of some endovascular aortic aneurysm repairs (EVARs). For the resolution of controversial issues and the determination of areas of uncertainty relating to these complications, a conference of 27 interested leaders was held on November 20, 2000.These 27 participants (21 vascular surgeons, five interventional radiologists, one cardiologist) had previously answered 40 key questions on endoleaks and endotension. At the conference, these 40 questions and participant answers were discussed and in some cases modified to determine points of agreement (consensus), near consensus (prevailing opinion), or disagreement.Conference discussion added two modified questions for a total of 42 key questions for the participants. Interestingly, consensus was reached on the answers to 24 of 42 or 57% of the questions, and near consensus was reached on 14 of 42 or 33% of the questions. Only with the answers to four of 42 or 10% of the questions was there persistent controversy or disagreement.The current endoleak classification system with some important modifications is adequate. Types I and II endoleak occur after 0 to 10% and 10% to 25% of EVARs, respectively. Many (30% to 100%) type II endoleaks will seal and have no detrimental effect, which never or rarely occurs with type I endoleaks. Not all endoleaks can be visualized with any technique, and increased pressure (endotension) can be transmitted through clot. Aneurysm pulsatility after EVAR correlates poorly with endoleaks and endotension. An enlarging aneurysm after EVAR mandates surgical or interventional treatment. These and other conclusions will help to resolve controversy and aid in the management of these vexing complications and should also point the way to future research in this field.

View details for DOI 10.1067/mva.2002.123095

View details for Web of Science ID 000175919100044

View details for PubMedID 12021724

Abstract

To assess elastin biosynthesis in the aortic wall in response to acute elevation of blood pressure, we studied the aortic gene expression of tropoelastin in a rabbit midthoracic aortic coarctation model. The time points of the study were 1, 3, and 7 days and 2, 4, and 8 weeks after coarctation. Additional animals were subjected to hypercholesterolemia for analysis of tropoelastin expression in the intimal lesion. mRNA for tropoelastin was quantitated by Northern blot analysis and its distribution was revealed by in situ hybridization. The 65-kDa tropoelastin was analyzed by Western blotting and immunohistochemistry. Tropoelastin mRNA proximal to the coarctation was increased at 2 weeks and returned to baseline by 8 weeks (P < 0.05 versus control). Changes in 65-kDa tropoelastin corresponded to those of mRNA. Tropoelastin gene was expressed mainly in the intima and in the outer media at the proximal region to the stenoses, which was particularly remarkable in the intimal lesion. The results indicate that tropoelastin gene expression was enhanced in the early remodeling response to elevated blood pressure. The distribution of newly synthesized tropoelastin in the outer media suggests a reenforcement role of tropoelastin, which preserves mechanical resiliency in response to changes in tensile stress.

View details for DOI 10.1006/exmp.2002.2423

View details for Web of Science ID 000175555400002

View details for PubMedID 11890720

Abstract

Arterial intimal thickening is consisted of predominately smooth muscle cells (SMC). The source of these SMCs and mechanisms response for their changes have not been well cleared. Using a model of rabbit common carotid artery (CCA) shear induced intimal thickening, we sought to identify and describe the source of SMCs in intima. The enlarged CCA 28 days after arteriovenous fistula (AVF) creation was subjected to subnormal wall shear stress (WSS) for 1, 3, and 7 days by closure of the AVF. To determine SMC proliferation, BrdU pulse labeling of SMCs was performed. BrdU-labeled SMCs were tracked over time to further confirm SMC migration. In response to subnormal WSS intimal thickening developed progressively. BrdU-labeled SMCs localized in the subendothelial area. When the BrdU-labeled medial SMCs were tracked 1 day after AVF closure, progenies of these BrdU-incorporated SMCs increased by 4.8-fold with 75% of them in the intima. They were 12-fold increased with 83% in the intima 7 days after. En face examination showed an accumulation of SMCs in internal elastic lamina gap after AVF closure, which later migrated into subendothelial area. In situ hybridization revealed increased TGF-beta1 mRNA expression in intimal SMCs. This study demonstrates that the medial SMCs are the predominant cells in subnormal WSS-induced intimal thickening. Early expression of TGF-beta1 may play an important role in the process of intimal thickening.

View details for DOI 10.1006/exmp.2002.2426

View details for Web of Science ID 000175555400006

View details for PubMedID 11890724

Abstract

Late onset graft or attachment site-related endoleaks may be hazardous, and early identification of patients at risk is important. We describe a patient who underwent implantation of a bifurcated stent graft 5.5 cm below the renal arteries because of a technical error with three extender cuffs implanted proximally to bridge the gap. During the 1st year, aneurysm diameter decreased from 68 to 52 mm. After 1 year, the patient had an acute endoleak develop, which originated between two of the extender cuffs and which was accompanied by severe abdominal pain and reexpansion of the aneurysm. This endoleak was treated with insertion of an additional bifurcated stent graft within the extender cuff segment. The patient has been subsequently followed for 6 months and has had no endoleak or symptoms, and aortic diameter has decreased once again to 55 mm.

View details for DOI 10.1067/mva.2002.119950

View details for Web of Science ID 000174468000027

View details for PubMedID 11877711

Abstract

To present a unique demonstration of postoperative perigraft contrast masquerading as an endoleak following endovascular abdominal aortic aneurysm (AAA) repair.A 66-year-old man underwent endovascular stent-graft repair of a 4.6-cm infrarenal AAA. The procedure was uncomplicated, and intraoperative completion angiography demonstrated good proximal and distal fixation of the stent-graft without an endoleak. A spiral computed tomographic (CT) angiogram obtained on postoperative day 2 revealed a large amount of extrastent contrast along the posterior aspect of the aneurysm sac. This defect had the appearance of an endoleak, but it was also present on the non-contrast images. A color-flow duplex examination performed on the same day showed a widely patent stent-graft with no evidence of extrastent flow.Contrast trapped in the aneurysm sac during endovascular aneurysm repair may be misinterpreted as an endoleak on postprocedural CT scans. "Pseudoendoleaks" can be distinguished from true endoleaks by examination of prebolus, noncontrast CT images, as well as by duplex ultrasound scanning.

View details for Web of Science ID 000174732000019

View details for PubMedID 11958315

Abstract

Intimal hyperplastic thickening (IHT) is a frequent cause of prosthetic bypass graft failure. Induction and progression of IHT is thought to involve a number of mechanisms related to variation in the flow field, injury and the prosthetic nature of the conduit. This study was designed to examine the relative contribution of wall shear stress and injury to the induction of IHT at defined regions of experimental end-to-side prosthetic anastomoses.The distribution of IHT was determined at the distal end-to-side anastomosis of seven canine Iliofemoral PTFE grafts after 12 weeks of implantation. An upscaled transparent model was constructed using the in vivo anastomotic geometry, and wall shear stress was determined at 24 axial locations from laser Doppler anemometry measurements of the near wall velocity under conditions of pulsatile flow similar to that present in vivo. The distribution of IHT at the end-to-side PTFE graft was determined using computer assisted morphometry. IHT involving the native artery ranged from 0.0+/-0.1 mm to 0.05+/-0.03 mm. A greater amount of IHT was found on the graft hood (PTFE) and ranged from 0.09+/-0.06 to 0.24+/-0.06 mm. Nonlinear multivariable logistic analysis was used to model IHT as a function of the reciprocal of wall shear stress, distance from the suture line, and vascular conduit type (i.e. PTFE versus host artery). Vascular conduit type and distance from the suture line independently contributed to IHT. An inverse correlation between wall shear stress and IHT was found only for those regions located on the juxta-anastomotic PTFE graft.The data are consistent with a model of intimal thickening in which the intimal hyperplastic pannus migrating from the suture line was enhanced by reduced levels of wall shear stress at the PTFE graft/host artery interface. Such hemodynamic modulation of injury induced IHT was absent at the neighboring artery wall.

View details for DOI 10.1115/1.1428554

View details for Web of Science ID 000175343500006

View details for PubMedID 11871604

Abstract

To evaluate the impact of a change in the manufacturing of the AneuRx stent-graft on the long-term results of endovascular abdominal aortic aneurysm (AAA) repair.The first 70 AAA patients treated with the AneuRx stent-graft between October 1996 and December 1998 were reviewed. The early stiff bifurcated design (STIFF) was used in 23 patients (mean age 71.7 +/- 9.3 years, range 45-87) and the current flexible bifurcated design (FLEX) in 47 mean age 75.0 +/- 7.3 years, range 61-96). Data on patient demographics, aneurysm morphology, technical success, complications, secondary procedures, and outcomes were compared using Kaplan-Meier estimates to evaluate patient survival and freedom from surgical conversion, rupture, and secondary interventions at 6, 12, and 24 months.The 2 groups were equally matched with regard to age, preoperative comorbidities, proximal neck dimensions, and aneurysm diameter. Mean follow-up times were 22.42 +/- 11.72 months (range 1-46) for the STIFF cohort and 18.08 +/- 6.14 months (range 1-30) for the FLEX (p = 0.057). Eleven (48%) of 23 STIFF patients required secondary interventions versus 6 (13%) of 47 FLEX patients (p < 0.05). There were no ruptures. At the 24-month interval, survival estimates were 86% for STIFF and 76% for FLEX (p = NS); freedom from surgical conversion was 100% for STIFF and 97% for FLEX (p = NS) and freedom from secondary interventions was 18% for STIFF and 90% for FLEX (p < 0.05) at 24 months.The AneuRx stent-graft was effective in achieving the primary objective of preventing aneurysm rupture in all patients. However, increasing the flexibility of the bifurcated module significantly improved the primary success rate by reducing the need for subsequent secondary interventions.

View details for Web of Science ID 000173089900009

View details for PubMedID 11797973

Abstract

The purpose of this study was to examine the effect of aortoiliac tortuosity, as assessed by observers and 3-dimensional (3D) computer-based methods, on the conduct and outcome of endovascular repair of abdominal aortic aneurysms.Infrarenal aortoiliac tortuosity was measured in 75 patients (mean follow-up, 14.8 +/- 10.4 months) who underwent endovascular repair of abdominal aortic aneurysms by using the following four methods: (1) grading by 2 experienced observers; (2) tortuosity index measured as the inverse radius of curvature (cm(-1)) at 1-mm intervals along the median luminal centerline (MLC) on 3D reconstructions of computed tomography (CT) angiograms and was calculated as the sum of values greater than 0.3 cm(-1); (3) MLC-straight line length ratio from renal to hypogastric arteries; (4) manual measurement of angles at points of angulation on anteroposterior and lateral projections of 3D CT reconstructions. In evaluating association between these measures, correlation between human observers was accepted as the gold standard.For rating of overall aortoiliac tortuosity, interobserver correlation (r = 0.67) was comparable with correlation of observers with tortuosity index (r = 0.67 and 0.56), whereas correlations of each observer with MLC-straight line ratio (r = 0.50 and 0.56) and cumulative angulation (r = 0.44 and 0.44) were significant but weaker. For determining the relative tortuosity of right and left aortoiliac access, agreement between observers and tortuosity index (54% and 58%; P < .05; kappa, 0.33 and 0.38) was not as good as between observers (68%; P < .001; kappa, 0.53). This difference was primarily related to evaluation of the aorta, where interobserver correlation (r = 0.71) was better than that between each observer and tortuosity index (r = 0.47 and 0.55), whereas correlations in the iliac arteries were comparable (r = 0.64 and 0.67) (all coefficients P < .01). Increased tortuosity was associated with a more complex endovascular repair, as reflected by longer fluoroscopy time (P = .05), use of more contrast material (P = .03), use of extender modules (P = .04), and more frequent use of arterial reconstruction (P = .01), but was not associated with a higher overall complication rate. Increased tortuosity, when it occurred in the aortic neck, was associated with predischarge endoleak (P = .03) but not with late endoleak, intervention, or aneurysm-related adverse events.Aortoiliac tortuosity is associated with increased complexity of endovascular aneurysm repair and with predischarge endoleak but does not appear to affect intermediate-term results. Computer-based 3D measurement of aortoiliac tortuosity is feasible and clinically meaningful. Its ultimate role in relation to human assessment must be further defined in future studies.

View details for Web of Science ID 000172020400005

View details for PubMedID 11668310

View details for DOI 10.1067/mva.2001.116966

View details for Web of Science ID 000172020400026

View details for PubMedID 11668331

Abstract

To determine the accuracy of helical computed tomography (CT), projectional angiography derived from CT angiography, and intravascular ultrasonographic withdrawal (IUW) length measurements for predicting appropriate aortoiliac stent-graft length.Helical CT data from 33 patients were analyzed before and after endovascular repair of abdominal aortic aneurysm (Aneuryx graft, n = 31; Excluder graft, n = 2). The aortoiliac length of the median luminal centerline (MLC) and the shortest path (SP) that remained at least one common iliac arterial radius away from the vessel wall were calculated. Conventional angiographic measurements were simulated from CT data as the length of the three-dimensional MLC projected onto four standard viewing planes. These predeployment lengths and IUW length, available in 24 patients, were compared with the aortoiliac arterial length after stent-graft deployment.The mean error values of SP, MLC, the maximum projected MLC, and IUW were -2.1 mm +/- 4.6 (SD) (P =.013), 9.8 mm +/- 6.8 (P <.001), -5.2 mm +/- 7.8 (P <.001), and -14.1 mm +/- 9.3 (P <.001), respectively. The preprocedural prediction of the postprocedural aortoiliac length with the SP was significantly more accurate than that with the MLC (P <.001), maximum projected MLC (P <.001), and IUW (P <.001).The shortest aortoiliac path length maintaining at least one radius distance from the vessel wall most accurately enabled stent-graft length prediction for 31 AneuRx and two Excluder stent-grafts.

View details for Web of Science ID 000169988700029

View details for PubMedID 11477256

Abstract

We investigated apoptosis of endothelial cells during the arterial narrowing process in response to reduction in flow. The decrease in flow was created in the carotid artery by closure of an arteriovenous fistula (AVF), which had been established for 28 days in rabbits. The endothelial cell apoptosis in the carotid artery was studied at 1, 3, 7, and 21 days of flow reduction after closure of the AVF by use of terminal deoxynucleotidyl transferase-mediated dUTP nick end-labeling (TUNEL) with laser scanning confocal microscopy and transmission and scanning electron microscopy. After AVF closure, arterial lumen diameter was reduced by 36%, and compared with endothelial cells before the closure, the number of endothelial cells was decreased by 45% at 21 days. Endothelial cell apoptosis was observed at 1 day, peaked at 3 days (381.3+/-87.1 cells per square millimeter), and decreased at 7 days. These cells had irregular protrusions under scanning electron microscopy and were characterized by fragmented nuclei under transmission electron microscopy. Apoptotic cells were mainly beneath the endothelium and were occasionally within smooth muscle cells and endothelial cells. The results suggest that apoptosis of endothelial cells may play a role in the arterial remodeling in response to a reduction in flow.

View details for Web of Science ID 000170005200009

View details for PubMedID 11451742

View details for Web of Science ID 000168383300027

View details for PubMedID 11319206

View details for Web of Science ID 000168549200001

View details for PubMedID 11357967

Abstract

Aortic aneurysms usually develop in the atherosclerosis prone infrarenal abdominal aorta. To assess the role of atherosclerosis in aortic enlargement, we studied the relation between plaque formation and aortic size in 30 pressure-fixed male cadaver aortas (age 40-95 years, mean age 67 years). Morphometric analysis of transverse sections of the mid-thoracic and the mid-abdominal aortas included measurement of intimal plaque area, lumen area, plaque and media thicknesses. The area encompassed by the internal elastic lamina area (IEL area) was taken to be an index of aortic size. IEL area increased with age at both the thoracic (r=0.77, P<0.01) and abdominal (r=0.54, P<0.01) aortic levels. The aorta also enlarged with increasing plaque area at the thoracic (r=0.73, P<0.01) and abdominal (r=0.79, P<0.01) levels. Regression analysis of IEL area on age, body weight, height and plaque area revealed that the primary predictor of thoracic aortic size was age, whereas the primary predictor of abdominal aortic size was plaque area. Plaque thickness in the abdominal aorta was greater than in the thoracic aorta (P<0.01). Increased plaque area was associated with a significant decrease in media thickness in the abdominal aorta (r=-0.75, P<0.01) but not in the thoracic aorta. Aortas with relatively enlarged abdominal segments, i.e. those with a thoracic to abdominal ratio of <1.2 (n=13), were compared to those with a normal ratio (> or =1.2, n=17). Relatively large abdominal aortas had twofold greater plaque area (P<0.001), reduced medial thickness (P<0.05), fewer medial elastic lamellae (P<0.01) and greater mural tensile stress (P<0.05) than relatively normal abdominal aortas. We conclude that plaque formation in the infrarenal abdominal aorta in humans is associated with aortic enlargement and decreased media thickness. These changes may be predisposing factors for the preferential development of subsequent aneurysmal dilation in the abdominal aorta.

View details for Web of Science ID 000167284900018

View details for PubMedID 11223437

Abstract

Despite successful surgical revascularization of ischemic limbs, a local and systemic reperfusion injury may occur after normal blood reperfusion. Recent experimental and clinical application of controlled limb reperfusion in Europe has demonstrated superior results, with lower morbidity and mortality. This new surgical technique includes modification of the reperfusate (calcium, pH, substrates, osmolarity, free radical scavenger) and the circumstances of initial reperfusion (time, temperature, pressure). This report describes the first application of controlled limb reperfusion after reperfusion injury. A 16-year-old boy underwent femoral access cardiopulmonary bypass for repeat cardiac repair with an ischemic time of 245 minutes. Postoperatively, severe ischemia/reperfusion syndrome developed with muscle contracture, immobility, and anesthesia of the right leg with a second ischemic time of about 6 hours. The systemic creatine phosphokinase level was 88,000 U/L; myoglobin was 27,000 ng/mL. He underwent controlled limb reperfusion by withdrawing blood from the aorta and mixing it with a crystalloid solution (calcium-reduced, hyperosmolar, hyperglycemic, alkalotic, glutamate- and aspartate-enriched, and containing a free radical scavenger) under controlled conditions (blood:crystalloid solution 6:1, for 30 minutes, reperfusion pressure < 50 mm Hg, and normothermia) before establishing normal blood reperfusion. Metabolic data from the central and femoral vein demonstrated a significant reduction of all previous elevated enzyme levels, avoidance of hyperkalemia, normalization of acidosis, and avoidance of systemic reperfusion injury with no multiorgan failure. Limb salvage was accomplished and functional recovery almost complete. To the authors' knowledge, this is the first application of controlled limb reperfusion reported in North America. With this surgical technique we were able to prevent metabolic local and systemic reperfusion changes after prolonged ischemia and also reduced previous reperfusion changes. This report confirms former experimental data, and further clinical studies are warranted.

View details for PubMedID 11668385

Abstract

The purpose of this study was to determine whether radiographically demonstrated proximal stent graft contour can be used as a marker for security of proximal neck fixation after endovascular aneurysm repair.Stent graft structure was examined in 100 consecutive patients with abdominal aortic aneurysms who were treated with the stent graft. Stent graft integrity, stent contour, angulation, compression, and position were assessed by use of plain abdominal radiography, and the results were correlated with contrast computed tomography (CT) scanning, clinical findings, and outcomes. Repeated imaging was carried out during follow-up of 3 to 38 (mean, 12) months.Stent graft repair was successful in all 100 patients. No stent fractures were identified. Concentric compression of the proximal portion of the stent graft was visible in 69% of patients and reflected deliberate oversizing of the stent graft at the time of implantation. In 5% of patients, a short eccentric compression deformity of the proximal stent was observed. This finding was associated with an increased risk of stent graft migration (P <.01) and with an increased risk for development of a late proximal (type I) endoleak (P <.01). Compared with CT scanning, abdominal radiography was less useful for assessment of short distances of migration (sensitivity 67%; specificity 79%). However, they provided better definition of the stent graft in relation to bony landmarks and better visualization of aortic calcification than CT with three-dimensional reconstruction.Plain abdominal radiographs are important in the postoperative evaluation of patients with aortic stent grafts. They allow for more precise evaluation of the structural elements of the stent graft than CT scanning and may disclose inadequate proximal fixation by demonstration of an eccentric compression deformity. They are less useful for assessment of migration.

View details for Web of Science ID 000167437400006

View details for PubMedID 11241116

Abstract

The objective was to review the current results of endovascular abdominal aortic aneurysm repair with the AneuRx stent graft and to determine the effectiveness of the device in achieving the primary objective of preventing aneurysm rupture.The outcome of all patients treated during the past 4 years in the U.S. AneuRx clinical trial was determined, and the worldwide clinical experience was reviewed.A total of 1192 patients were treated with the AneuRx stent graft during all phases of the U.S. Clinical Trial from June 1996 to November 1999, with follow-up extending to June 2000. Ten (0.8%) patients have had aneurysm rupture, with most ruptures (n = 6) occurring in 174 (3.4%) patients treated with an early stiff bifurcation stent graft design used in phase I and in the initial stages of phase II. Since the current, flexible, segmented bifurcation stent graft design was introduced, four (0.4%) ruptures have occurred among 1018 patients treated. Of these, one was during implantation, two were placed too far below the renal arteries, and one patient refused treatment of a type I endoleak. Kaplan-Meier analysis of all 1192 patients treated with the AneuRx stent graft including both stent graft designs revealed the patient survival rate to be 93% at 1 year, 88% at 2 years, and 86% at 3 years, freedom from conversion to open repair to be 98% at 1 year, 97% at 2 years, and 93% at 3 years, and freedom from secondary procedure to be 94% at 1 year, 92% at 2 years, and 88% at 3 years. Freedom from aneurysm rupture with the commercially available segmented bifurcation stent graft was 99.7% at 1 year, 99.5% at 2 years, and 99.5% at 3 years. The presence or absence of endoleak on contrast computed tomography scanning after stent graft placement was not found to be a significant predictor of long-term outcome measures. Worldwide experience with the AneuRx device now approaches 10,000 patients.Endovascular management of abdominal aortic aneurysms with the AneuRx stent graft has markedly reduced the risk of aneurysm rupture while eliminating the need for open aneurysm surgery in 98% of patients at 1 year and 93% of patients at 3 years. The device was effective in preventing aneurysm rupture in 99.5% of patients over a 3-year period. The overall patient survival rate was 93% at 1 year and 86% at 3 years.

View details for Web of Science ID 000167332500020

View details for PubMedID 11174825

View details for Web of Science ID 000166906000015

View details for PubMedID 11220725

Abstract

The purpose of this study was to assess atherosclerotic plaque deposition and aortic wall responses in the abdominal aorta in relation to the development of aneurysmal and occlusive disease in the infrarenal aorta.Morphologic differences at five standardized locations in the infrarenal aorta in 67 pressure perfusion-fixed male cadaver aortas (aged, 41-98 years; mean, 66 years) were studied and compared with the supraceliac segment. Quantitative computer-assisted morphometry of histologic sections included measurement of plaque area, lumen area, lumen diameter, media thickness, number of medial elastic lamellae, and the area encompassed by the internal elastic lamina that best represents the artery size of each segment. The ratio of the supraceliac segment to the midabdominal segment (normally greater than 1.3) was used to define three groups: Group I (normal): ratio greater than or equal to 1.30 (n = 31); Group II (intermediate): ratio greater than or equal to 1.20 but less than 1.30 (n = 20); and Group III: ratio less than 1.20 (n = 16), which represented dilated midabdominal aortas. There was no significant difference in age among the groups.Group I had minimal intimal plaque and little gross evidence of atherosclerosis. Group II had increased intimal plaque compared with Group I (P <.01) and gross evidence of atherosclerosis, which was maximally localized in the distal aorta; there was no aortic enlargement or thinning of the media underneath the plaque. Group III had more intimal plaque than Group I (P <.01) and Group II (P <.01) and was associated with localized aortic enlargement and media thinning compared with Group I (P <.05) and Group II (P <.01). Increasing intimal plaque in Group III correlated with an increase in lumen diameter (r = 0.61, P <.05), but this relationship was not significant in Group I and Group II. The aortic media in Group III had a reduced number of medial elastic lamellae, was reduced in thickness, and was more exposed to increased wall stress than the aortas in Groups I and II.These results suggest that there may be different local responses to atherosclerosis in the abdominal aorta in human beings. Plaque deposition associated with localized dilation, thinning of the media, and loss of medial elastic lamellae may predispose that segment of aorta to subsequent aneurysm formation. Plaque deposits without media thinning, without loss of elastic lamellae, and without artery wall dilation may predispose the aorta, in the event of continuing plaque accumulation, to the development of lumen stenosis.

View details for Web of Science ID 000166576900021

View details for PubMedID 11137928

Abstract

We conducted a novel quantitative three-dimensional analysis of computed tomography (CT) angiograms to establish the relationship between aortic geometry and age, sex, and body surface area in healthy subjects.Abdominal helical CT angiograms from 77 healthy potential renal donors (33 men/44 women; mean age, 44 years; age range, 19-67 years) were selected. In each dataset, orthonormal cross-sectional area and diameter measurements were obtained at 1-mm intervals along the automatically calculated central axis of the abdominal aorta. The aorta was subdivided into six consecutive anatomic segments (supraceliac, supramesenteric, suprarenal, inter-renal, proximal infrarenal, and distal infrarenal). The interrelated effects of anatomic segment, age, sex, and body surface area on cross-sectional dimensions were analyzed with linear mixed-effects and varying-coefficient statistical models.We found that significant effects of sex and of body surface area on aortic diameters were similar at all anatomic levels. The effect of age, however, was interrelated with anatomic position, and gradually decreasing slopes of significant diameter-versus-age relationships along the aorta, which ranged from 0.14 mm/y (P <.0001) proximally to 0.03 mm/y (P =.013) distally in the abdominal aorta, were shown.The abdominal aorta undergoes considerable geometric changes when a patient is between 19 and 67 years of age, leading to an increase of aortic taper with time. The hemodynamic consequences of this geometric evolution for the development of aortic disease still need to be established.

View details for Web of Science ID 000166576900022

View details for PubMedID 11137929

Abstract

The purpose of this study was to compare duplex ultrasound scanning and computed tomographic (CT) angiography for postoperative imaging and surveillance after endovascular repair of abdominal aortic aneurysm (AAA).One hundred consecutive patients with AAA underwent endovascular (Medtronic AneuRx, stent graft) aneurysm repair and were imaged with both CT angiography and duplex ultrasound scanning at regular intervals after the procedure. Each imaging modality was evaluated for technical adequacy and for documentation of aneurysm size, endoleak, and graft patency. In concurrent scan pairs, accuracy of duplex scanning was compared with CT.A total of 268 CT scans and 214 duplex scans were obtained at intervals of 1 to 30 months after endovascular aneurysm repair (mean follow-up interval, 9+/-7 months). All CT scans were technically adequate, and 198 (93%) of 214 duplex scans were technically adequate for the determination of aneurysm size, presence of endoleak, and graft patency. Concurrent (within 7 days of each other) scan pairs were obtained in 166 instances in 76 patients (1-6 per patient). The maximal transverse aneurysm sac diameter measured with both methods correlated closely (r = 0.93; P <.001) without a significant difference on paired analysis. In 92% of scans, measurements were within 5 mm of each other. Diagnosis of endoleak on both examinations correlated closely (P <.001), and compared with CT, duplex scanning had a sensitivity of 81%, a specificity of 95%, a positive predictive value of 94%, and a negative predictive value of 90%. Discordant results occurred in 8% of examinations, and in none of these was the endoleak close to the attachment sites or associated with aneurysm expansion. An endoleak was demonstrated on both tests in all eight patients who had an endoleak judged severe enough to warrant arteriography. Graft patency was documented in each instance, without discrepancy, with both modalities.High-quality duplex ultrasound scanning is comparable to CT angiography for the assessment of aneurysm size, endoleak, and graft patency after endovascular exclusion of AAA.

View details for Web of Science ID 000165847400021

View details for PubMedID 11107086

Abstract

We studied the mural distribution of collagen types I and III and tropoelastin in enhanced experimental atherogenesis induced in rabbits by hyperlipidemia superimposed by hypertension. Animals were fed a high-cholesterol diet for 5 weeks and also subjected to midthoracic aortic coarctation for 4 weeks. Serum cholesterol levels were increased and blood pressure was elevated proximal to the coarctation. Foam cell lesions developed in the aorta proximal to the coarctation. In situ hybridization and immunohistochemistry showed that gene expression of collagen types I and III and tropoelastin was upregulated, with a differential distribution across the arterial wall. New collagen type I was mainly distributed in the intima, the outer media, and the adventitia. New collagen type III was spread more uniformly across the wall, including the adventitia, whereas tropoelastin was mainly localized in intimal foam cell lesions. Morphometric data showed an increase in wall thickness. These results suggest that collagen types I and III play a role in remodeling of the aortic wall in response to hypertension. The remarkable involvement of the adventitia in this response indicates that the adventitia is an important component of the arterial wall. Tropoelastin is closely associated with foam cell lesion formation, suggesting a role for this component in atherogenesis as well.

View details for Web of Science ID 000165869900016

View details for PubMedID 11116054

Abstract

Hypertension is a well-known risk factor for coronary artery disease and carotid and lower extremity occlusive disease. Surgically induced hypertension in hypercholesterolemic animals results in increased aortic wall motion and increased plaque formation. We tested the hypothesis that reduction in aortic wall motion, despite continued hypertension, could reduce plaque formation. New Zealand White rabbits (n=26) underwent thoracic aortic banding to induce hypertension and were fed an atherogenic diet for 3 weeks. In 13 rabbits, a segment of aorta proximal to an aortic band was externally wrapped to reduce wall motion. All animals were fed an atherogenic diet for 3 weeks. Four groups were studied: 1, coarctation control (no wrap, n=7); 2, coarctation with loose wrap (n=6); 3, coarctation with firm wrap (n=7); and 4, control (noncoarcted, n=6). Wall motion, blood pressure, and pulse pressure were measured at standard reference sites proximal and distal to the coarctation by use of intravascular ultrasound. Quantitative morphometry was used to measure intimal plaque. Mean arterial pressure and cyclic aortic wall motion were equally increased proximal to the aortic coarctation in all 3 coarcted rabbit groups compared with the control group (P:<0.001). Wall motion in the segment of aorta under the loose and firm wraps was no different from the control value. The external wrap significantly reduced intimal thickening in the 4 groups by the following amounts: group 1, 0.30+/-0.03 mm(2); group 2, 0.06+/-0.02 mm(2); group 3, 0. 04+/-0.02 mm(2); and group 4, 0.01+/-0.01 mm(2) (P:<0.001). Localized inhibition of aortic wall motion in the lesion-prone hypertensive aorta resulted in significant reduction in intimal plaque formation. These data suggest that arterial wall cyclic motion may stimulate cellular proliferation and lipid uptake in experimental atherosclerosis.

View details for Web of Science ID 000089333600019

View details for PubMedID 10978259

Abstract

The purpose of this study was to determine the rate of eligibility among patients with abdominal aortic aneurysms (AAAs) considered for endovascular repair and to examine the effect of an endovascular program on the institutional pattern of AAA repair.All patients evaluated for endovascular AAA repair since the inception of an endovascular program were reviewed for determination of eligibility rates and eventual treatment. Open AAA repairs were categorized as simple (uncomplicated infrarenal), complex (juxtarenal, suprarenal, thoracoabdominal, infected), or ruptured, and their rates before and after initiation of an endovascular program were compared.Over 3 years, 324 patients were considered for endovascular AAA repair; 176 (54%) were candidates, 138 (43%) were not candidates, and 10 (3%) did not complete the evaluation. The rate of eligibility increased significantly from 45% (66/148 patients) during the first half of this period to 63% (110/176 patients) during the second half (P <. 001). Candidates were significantly younger (74.4 +/- 7.6 years) than noncandidates (78.3 +/- 6.7 years) (P <.01), and their aneurysm diameter tended to be smaller (57.6 +/- 9.2 mm compared with 60.8 +/- 12.3 mm; P =.06). The most common reason for ineligibility was an inadequate proximal aortic neck. Of 176 candidates, 78% underwent endovascular repair, and 6% underwent open repair. Of 138 noncandidates, 56% underwent surgical repair. Over a period of 6 years, 542 patients with AAAs (429 simple, 86 complex, 27 ruptured) underwent open repair. The total number and ratio of simple to complex open repairs for nonruptured aneurysms during the 3 years before the initiation of the endovascular program (213 simple, 44 complex) were not significantly different from the repairs over the subsequent 3-year period (216 simple, 42 complex). Similarly, no difference in the total number and the ratio of simple to complex open repairs was found between the first and the second 18-month periods since the initiation of the endovascular program.The rate of eligibility of patients with AAA for endovascular repair appears to be higher than previously reported. The presence of an active endovascular program has not decreased the number or shifted the distribution of open AAA repair.

View details for Web of Science ID 000089230100023

View details for PubMedID 10957658

View details for PubMedID 10931815

Abstract

Untreated abdominal aortic aneurysms (AAAs) enlarge at a mean rate of 3.9 mm/y with great individual variability. We sought to determine the effect of endovascular repair on the rate of change in aneurysm size.There were 110 patients who underwent endovascular AAA repair at Stanford University Medical Center and who were followed up for 1 to 30 months (mean, 10 months) with serial contrast-infused helical computed tomography (CT). Maximal aneurysm diameter was determined using two independent methods: (1) measured manually, from cross-sectional computed tomography (XSCT) angiograms and (2) calculated from quantitative three-dimensional computed tomography (3DCT) data as orthonormal diameter.Maximal cross-sectional aneurysm diameter measured by hand (XSCT) and calculated as orthonormal values (3DCT) correlated closely (r = 0.915; P <.001). The XSCT-measured diameter was larger by 2.3 +/- 3. 75 mm (P <.001), and the 95% CI for SE of the bias was 1.85 to 2.75 mm. Preoperative aneurysm diameter (XSCT 59.1 +/- 8.4 mm; 3DCT 58.1 +/- 9.3 mm) did not differ significantly from the initial postoperative diameter. Considering all patients, XSCT diameter decreased at a rate of 0.34 +/- 0.69 mm/mo, and 3DCT diameter decreased at a rate of 0.28 +/- 0.79 mm/mo. Aneurysms in patients without endoleaks had a higher rate of decrease, an XSCT diameter by 0.50 +/- 0.74 mm/mo, and 3DCT diameter by 0.46 +/- 0.84 mm/mo. In these patients, mean absolute decrease in diameter at 6 months was 3. 4 +/- 4.5 mm (XSCT) and 3.3 +/- 5.9 mm (3DCT) and at 12 months, 5.9 +/- 5.7 mm (XSCT) and 5.4 +/- 5.7 mm (3DCT). Aneurysms in patients with persistent endoleaks did not change in mean XSCT diameter, and 3DCT diameter increased by 0.12 +/- 0.52 mm/mo (not significant). Aneurysm diameter remained within 4 mm of original size in 68% (3DCT) to 71% (XSCT) of patients. In one patient, aneurysm diameter increased (XSCT and 3DCT) more than 5 mm. Four patients who had a new onset endoleak had a much higher expansion rate than those with a chronic endoleak (P <.05).The rate of decrease in aneurysm size (annualized 3.4-4.1 mm/y) after endovascular repair of AAA approximates the reported expansion rate in untreated aneurysms. However, individual aneurysm behavior is unpredictable, and the presence of an endoleak is unreliable in predicting changes in diameter. New onset endoleaks are associated with an enlargement rate greater than that of untreated aneurysms.

View details for Web of Science ID 000088172500021

View details for PubMedID 10876211

View details for PubMedID 10873013

Abstract

The purpose of this study was to determine the cause and frequency of aneurysm rupture after endovascular aneurysm repair.We reviewed each patient who sustained aneurysm rupture among all patients enrolled for endovascular aortic aneurysm repair in phases I, II, and III of the US AneuRx Multicenter Clinical Trial from June 1996 through October 1999.A total of 1067 patients were enrolled for endovascular aneurysm repair. The AneuRx stent graft was successfully implanted in 1046 patients (98%). Endovascular repair was unsuccessful in 21 patients (2%); 13 patients (1%) were converted to open aneurysm repair. Among these, two patients (0.2%) sustained aneurysm rupture due to procedure-related instrumentation and underwent open surgical conversion. Aneurysm rupture has occurred in seven patients (0.7%) 3 weeks to 24 months (mean, 16 months) after successful endovascular repair. Four patients survived open surgical repair, and three patients died within 30 days. Overall rupture-related mortality was 0.5% and included late deaths after rupture. Before rupture, two patients had endoleak and aneurysm enlargement, and five patients had no endoleak and no aneurysm enlargement. After aneurysm rupture all seven patients had evidence suggesting that there was poor fixation of the stent graft at the proximal distal, or iliac junction fixation sites. The two patients with endoleak declined recommended open surgical or endovascular repair, which could have prevented aneurysm rupture. In retrospect, the five patients without endoleak could potentially have avoided rupture with better patient selection, better stent graft positioning, or reinforcement of fixation points with stent graft extenders. The probability of no aneurysm rupture for all patients undergoing endovascular repair is 0.996 +/- 0.002 at 1 year and 0.974 +/- 0.011 at 2 years by life table analysis with the longest follow-up of 41 months.The early risk of aneurysm rupture after endovascular aneurysm repair is low. However, the possibility of rupture persists even in patients with no endoleak after the procedure. Therefore, all patients treated with endovascular aneurysm repair should continue to be monitored after the procedure. Patients with evidence suggesting insecure stent graft fixation should undergo further endovascular treatment or open surgical repair.

View details for Web of Science ID 000087109900015

View details for PubMedID 10805887

Abstract

To assess the effects on the biosynthesis of collagen types I and III associated with an acute increase in blood pressure, we established a mid-thoracic aortic coarctation in the rabbit and studied gene expression and protein accumulation of these collagen types proximal to the stenosis 1, 3 and 7 days and 2, 4 and 8 weeks after coarctation. The mRNA level of type I collagen pro-alpha2(I) was maximal at 3 days and returned to normal at 4 weeks. mRNA of pro-alpha2(I) was localized mainly in the outer media, adventitia and intima. Accumulation of type I collagen and its precursors was increased by 3 days, peaked at 4 weeks, and decreased toward normal by 8 weeks, corresponding to the distribution of pro-alpha2(I) mRNA. Gene expression for pro-alpha1(III) was similar to that of pro-alpha2(I) but was distributed throughout the media. We conclude that the mechanical stresses associated with an acutely induced alteration in pressure initiate rapid gene expression for collagen types I and III in the aortic wall. The response for collagen type I, predominantly in the outer media and adventitia, suggests that these regions play an immediate role in the resistance to excessive dilatation of the aorta. The diffuse response for collagen type III in the media suggests participation in a more extensive remodeling response associated with the reinforcement and reorganization of the musculo-elastic fascicles.

View details for Web of Science ID 000087620000003

View details for PubMedID 10859475

View details for Web of Science ID 000087080200036

View details for PubMedID 10823542

View details for Web of Science ID 000085296100001

View details for PubMedID 10664489

View details for Web of Science ID 000083335200049

View details for PubMedID 10551612

View details for Web of Science ID 000085006700004

View details for PubMedID 10893132

Abstract

Gaps in the internal elastic lamina (IEL) have been observed in arteries exposed to high blood flow. To characterize the nature and consequences of this change, blood flow was increased in the carotid arteries of 56 adult, male, Japanese white rabbits by creating an arteriovenous fistula between the common carotid artery and the external jugular vein. The common carotid artery proximal to the arteriovenous fistula was studied at intervals from 1 hour to 8 weeks after exposure to high flow. In the controls, the IEL showed only the usual, small, physiological holes, 2 to 10 microm in diameter. At 3 days, some of the holes in the IEL had become enlarged, but they could not be detected by scanning electron microscopy, despite manifest endothelial cell proliferation. At 4 days, gaps in the IEL appeared as small, luminal surface depressions, 15 to 50 microm wide. At 7 days, the gaps in the IEL had enlarged and formed circumferential, luminal depressions occupying 15+/-5% of the lumen surface. Endothelial cell proliferation persisted in the gaps while proliferative activity decreased where the IEL remained intact. At 4 weeks, as the artery became elongated and dilated, the gaps in the IEL widened as intercommunicating circumferential and longitudinal luminal depressions occupying 64+/-5% of the lumen surface. At 8 weeks, the rate of elongation and dilatation of the artery slowed and the widening of the gaps in the IEL diminished. Endothelial cells covered the gaps throughout. We conclude that flow-induced arterial dilatation is accompanied by an adaptive remodeling of the intima. The gaps in the IEL permit an increase in lumen surface area while endothelial cell proliferation assures a continuous cell lining throughout.

View details for Web of Science ID 000083152500003

View details for PubMedID 10521357

Abstract

To present novel techniques to prevent spinal ischemia during aneurysm creation and chronic bifurcated stent-graft implantation in an ovine model of abdominal aortic aneurysm (AAA).Experimental AAAs were created in 38 sheep. To prevent spinal ischemia, an internal aortic shunt was used during aneurysm creation. In the animals designated to receive bifurcated stent-grafts, a left external iliac-to-internal iliac bypass was performed to revascularize the caudal artery and prevent postdeployment spinal cord ischemia. Specimens were harvested at 1 week, 1, 3, and 6 months, and 1 year.Aneurysms were successfully created without paralysis in 35 animals. Two died due to aspiration pneumonia. Of the 33 animals implanted with endografts, 16 (94%) of 17 with straight devices and 15 (94%) of 16 with bifurcated stent-grafts survived with well-functioning, patent stent-grafts. Paralysis developed in 2 animals after endografting due to technical failures.The use of an internal shunt during aneurysm creation and internal iliac-to-external iliac transposition prior to bifurcated stent-graft deployment prevented spinal ischemia in an ovine AAA model. Chronically deployed stent-grafts were well tolerated.

View details for Web of Science ID 000083522700011

View details for PubMedID 10495157

View details for Web of Science ID 000080864800030

View details for PubMedID 10359949

Abstract

The beneficial effect of exercise in the retardation of the progression of cardiovascular disease is hypothesized to be caused, at least in part, by the elimination of adverse hemodynamic conditions, including flow recirculation and low wall shear stress. In vitro and in vivo investigations have provided qualitative and limited quantitative information on flow patterns in the abdominal aorta and on the effect of exercise on the elimination of adverse hemodynamic conditions. We used computational fluid mechanics methods to examine the effects of simulated exercise on hemodynamic conditions in an idealized model of the human abdominal aorta.A three-dimensional computer model of a healthy human abdominal aorta was created to simulate pulsatile aortic blood flow under conditions of rest and graded exercise. Flow velocity patterns and wall shear stress were computed in the lesion-prone infrarenal aorta, and the effects of exercise were determined.A recirculation zone was observed to form along the posterior wall of the aorta immediately distal to the renal vessels under resting conditions. Low time-averaged wall shear stress was present in this location, along the posterior wall opposite the superior mesenteric artery and along the anterior wall between the superior and inferior mesenteric arteries. Shear stress temporal oscillations, as measured with an oscillatory shear index, were elevated in these regions. Under simulated light exercise conditions, a region of low wall shear stress and high oscillatory shear index remained along the posterior wall immediately distal to the renal arteries. Under simulated moderate exercise conditions, all the regions of low wall shear stress and high oscillatory shear index were eliminated.This numeric investigation provided detailed quantitative data on the effect of exercise on hemodynamic conditions in the abdominal aorta. Our results indicated that moderate levels of lower limb exercise are necessary to eliminate the flow reversal and regions of low wall shear stress in the abdominal aorta that exist under resting conditions. The lack of flow reversal and increased wall shear stress during exercise suggest a mechanism by which exercise may promote arterial health, namely with the elimination of adverse hemodynamic conditions.

View details for Web of Science ID 000080864800023

View details for PubMedID 10359942

Abstract

The results of a prospective, nonrandomized, multicenter clinical trial that compared endovascular stent graft exclusion of abdominal aortic aneurysms with open surgical repair are presented. During an 18-month period, 250 patients with infrarenal aneurysms underwent treatment at 12 study sites-190 patients underwent endovascular repair using the Medtronic AneuRx stent graft (Sunnyvale, Calif), and 60 underwent open surgical repair. There was no significant difference in operative mortality rates between the groups. The patients who underwent stent grafting had significant reductions in blood loss, time to extubation, and days in the intensive care unit and in the hospital, with an earlier return to function. The major morbidity rate was reduced from 23% in the surgery group to 12% (P <. 05) in the stent graft group. There was no difference in the combined morbidity/mortality rates between the two groups. Primary technical success at the time of discharge for the patients with stent grafts was 77%, largely as a result of a 21% endoleak rate. At 1 month, the endoleak rate had decreased to 9%. There was no difference in the primary or secondary procedure success rates at 30 days between the surgery and stent graft groups. The primary graft patency rate at 6 months was 98% in the surgery group and 97% in the stent graft group. The aneurysm exclusion rate at 1 month and 6 months was 100% in patients who underwent surgery and 91% in patients who underwent stent grafting. Stent graft migration occurred in three patients and resulted in late endoleaks; each endoleak was corrected by means of endovascular placement of a stent graft extender cuff. There have been no aneurysm ruptures and no surgical conversions to open repair in the stent graft group. Stent graft repair compares favorably with open surgical repair, with a reduced morbidity rate, shortened hospital stays, and satisfactory short term outcomes.

View details for Web of Science ID 000078528900018

View details for PubMedID 9950987

View details for PubMedID 10477660

Abstract

The current paradigm for surgery planning for the treatment of cardiovascular disease relies exclusively on diagnostic imaging data to define the present state of the patient, empirical data to evaluate the efficacy of prior treatments for similar patients, and the judgement of the surgeon to decide on a preferred treatment. The individual variability and inherent complexity of human biological systems is such that diagnostic imaging and empirical data alone are insufficient to predict the outcome of a given treatment for an individual patient. We propose a new paradigm of predictive medicine in which the physician utilizes computational tools to construct and evaluate a combined anatomic/physiologic model to predict the outcome of alternative treatment plans for an individual patient. The predictive medicine paradigm is implemented in a software system developed for Simulation-Based Medical Planning. This system provides an integrated set of tools to test hypotheses regarding the effect of alternate treatment plans on blood flow in the cardiovascular system of an individual patient. It combines an Internet-based user interface developed using Java and VRML, image segmentation, geometric solid modeling, automatic finite element mesh generation, computational fluid dynamics, and scientific visualization techniques. This system is applied to the evaluation of alternate, patient-specific treatments for a case of lower extremity occlusive cardiovascular disease.

View details for PubMedID 10581521

Abstract

The infrarenal abdominal aorta is particularly prone to atherosclerotic plaque formation while the thoracic aorta is relatively resistant. Localized differences in hemodynamic conditions, including differences in velocity profiles, wall shear stress, and recirculation zones have been implicated in the differential localization of disease in the infrarenal aorta. A comprehensive computational framework was developed, utilizing a stabilized, time accurate, finite element method, to solve the equations governing blood flow in a model of a normal human abdominal aorta under simulated rest, pulsatile, flow conditions. Flow patterns and wall shear stress were computed. A recirculation zone was observed to form along the posterior wall of the infrarenal aorta. Low time-averaged wall shear stress and high shear stress temporal oscillations, as measured by an oscillatory shear index, were present in this location, along the posterior wall opposite the superior mesenteric artery and along the anterior wall between the superior and inferior mesenteric arteries. These regions were noted to coincide with a high probability-of-occurrence of sudanophilic lesions as reported by Cornhill et al. (Monogr. Atheroscler. 15:13-19, 1990). This numerical investigation provides detailed quantitative data on hemodynamic conditions in the abdominal aorta heretofore lacking in the study of the localization of atherosclerotic disease.

View details for Web of Science ID 000077056000007

View details for PubMedID 9846936

Abstract

Nationally, results of renal transplantation in infants are inferior to those in older children and adults. Within the infant group, best results are obtained with adult-sized kidneys (ASKs) rather than size-compatible pediatric kidneys. However, transplantation of ASKs into infants has an increased risk of acute tubular necrosis and graft loss from vascular thrombosis and primary nonfunction. The aim of this study was to define and understand the hemodynamic changes induced by ASK transplantation, so that outcomes of transplantation in infants can be improved.Nine hemodynamically stable and optimally hydrated infants were studied under a controlled sedation with cine phase-contrast magnetic resonance at three time periods: before transplantation, 8-12 days after transplantation, and 4-6 months after transplantation. Cross-sectional images of both the infant aorta and the adult transplant renal artery were obtained and blood flow was quantitated. Renal volumes were also obtained, and expected renal artery blood flow based on early posttransplant volume was calculated. In addition, renal artery blood flow was determined in 10 in situ native adult kidneys prior to donor nephrectomy. Supplemental nasogastric or gastrostomy tube feeding was carried out during the blood flow study period to optimize intravascular volume.Mean infant aortic blood flows were 331+/-148 ml/min before transplantation, 761+/-272 ml/ min at 8-12 days after transplantation (P=0.0006 with pretransplant flow), and 665+/-138 ml/min at 4-6 months after transplantation (P=0.0001 with pretransplant flow). Mean transplanted renal artery flows were 385+/-158 ml/min at 8-12 days and 296+/-113 ml/min at 4-6 months after transplantation. Transplanted renal artery flows were less than prenephrectomy in situ donor renal artery blood flow (618+/-130 ml/min; P=0.02 and P=0.0003) and expected normal renal artery blood flow (666+/-87 ml/min; P=0.003 and P=0.001) at both 8-12 days and 4-6 months after transplantation. A 26% reduction in renal volume (P=0.003) occurred between the two postoperative time periods, and this paralleled the decrease in posttransplant renal artery flow. One-year graft and patient survival in the nine infants was 100%. The mean serum creatinine levels at 3, 6, and 12 months were 0.43+/-0.10, 0.48+/-0.15, and 0.49+/-0.16 mg/dl.This study is the first to quantitatively document the blood flow changes occurring after ASK transplantation in infants. There was a greater than two-fold increase in aortic blood flow after ASK transplantation, and this increase was sustained for at least 4 months and appeared to be driven by the blood flow demand of the ASK. However, actual posttransplant renal artery blood flow was significantly less than normal renal artery flow. Our study suggests that aggressive intravascular volume maintenance may be necessary to achieve and maintain optimum aortic blood flow, so as not to further compromise posttransplant renal artery flow and to avoid low-flow states that could induce acute tubular necrosis, vascular thrombosis, or primary nonfunction.

View details for Web of Science ID 000076585400001

View details for PubMedID 9798687

Abstract

To assess the effect of chronic, repetitive increases and decreases in blood flow on an artery.Arteriovenous fistulae were created in Japanese male rabbits between the left common carotid artery and the corresponding external jugular vein. Animals were placed into either control groups or one of six cycle groups consisting of flow variations (0.5 cycles, 1.0 cycle, 1.5 cycles, 2.0 cycles, 2.5 cycles and 3.0 cycles). Each complete cycle consisted of 4 weeks of increased flow followed by 6 weeks of normalised flow by fistula ligation.Arteries exposed to increased flow for 4 weeks (0.5 cycles) had a significant increase in lumen diameter without intimal thickening. After 6 weeks of normalised flow (1.0 cycle), shear stress became subnormal (0.42 +/- 0.17 N/m2), intimal thickening developed. In subsequent cycles, intimal thickening continued to develop with each point of flow normalisation and reduction in shear stress. Histologic and ultrastructural analysis revealed endothelial cells preservation at all time points, with individual strata of smooth muscle cell proliferation in the intima corresponding to the cycle numbers.Progressive intimal thickening occurred in the previously flow-induced remodelled artery when shear stress was reduced to subnormal levels with preserved endothelium, but was inhibited by high flow periods.

View details for Web of Science ID 000076751000005

View details for PubMedID 9818007

View details for Web of Science ID 000075447000021

View details for PubMedID 9714626

Abstract

We administered a specific, nonselective matrix metalloproteinase (MMP) inhibitor (RS-113,456) to examine the effect of MMP inhibition on flow-mediated arterial enlargement in a rodent arteriovenous fistula (AVF) model.Four groups of male Sprague-Dawley rats were created: sham (sham operated; n = 10), control (2.0 mm left common femoral AVF alone; n = 16), vehicle (AVF plus 0.5 mL vehicle orally twice a day; n = 20), and treatment (AVF plus 25 mg/kg RS-113,456 in 0.5 mL vehicle orally twice a day; n = 16). Heart rate, mean arterial pressure, and body weight were recorded on postoperative days 0, 7, 14, and 21. On day 21, AVF patency was confirmed, the infrarenal aorta and common iliac arteries were exposed, blood flow velocity and external diameter were measured, and wall shear stress (WSS) was calculated. Analysis was performed by paired, two-tailed Student t test, one-way analysis of variance, and the Bonferroni/Dunn procedure for post hoc testing.Heat rate, mean arterial pressure, and weight did not vary at any time between groups. Aortic and left iliac diameter was larger in the AVF groups than in sham groups (P < .001), and control and vehicle groups were larger than treatment groups (P < .0001). Changes in aortic and left iliac flow were also significant (AVF was more than sham and control, and vehicle was more than treatment). No difference in aortic and left iliac artery velocity and WSS or right iliac diameter, velocity, flow, or WSS was observed between groups.MMP inhibition diminishes flow-mediated arterial enlargement in the rat AVF model.

View details for Web of Science ID 000075252200054

View details for PubMedID 9706156

Abstract

Arteries enlarge in response to increased blood flow, but the molecular signals controlling this enlargement are not well understood. Basic fibroblast growth factor (bFGF) is a potent mitogen for endothelial cells (EC) and smooth muscle cells (SMC) and promotes cellular proliferation and differentiation. In order to determine whether bFGF is expressed in response to increased blood flow in vivo, carotid-jugular arteriovenous fistulas (AVF) were created in Japanese white rabbits. The carotid artery proximal to the fistula was harvested after 1, 3, or 7 days and compared to nonoperated, control carotid arteries. Arterial blood flow increased five- to eightfold in all AVF animals and resulted in a significant increase in wall shear stress. The proximal carotid artery arterial diameter was no different from control after 1 and 3 days (2.3 +/- 0. 1 mm) but enlarged to 2.9 +/- 0.1 mm (P < 0.05) after 7 days. RT-PCR revealed early transcription of bFGF mRNA at 1 and 3 days with increased densitometric band ratio (bFGF/beta-actin) at 7 days. Immunohistochemical analysis revealed bFGF protein localization in EC of control arteries as well as AVF arteries at all time points. SMC and adventitia expression of bFGF was absent in controls, minimal at 1 day, and increased after 3 and 7 days in the experimental groups. Western blotting confirmed the presence of bFGF in samples and transmission immunoelectron microscopy confirmed its nuclear localization. Endothelial cells in vivo express bFGF under both normal and elevated flow conditions. Smooth muscle cells, however, do not express bFGF under normal flow conditions but begin to express bFGF after 1 day of high flow with increased expression after 3 and 7 days. Flow-induced arterial enlargement begins after SMC expression of bFGF. Therefore, bFGF may play a role in arterial enlargement and adaptive remodeling in response to increased flow.

View details for Web of Science ID 000075746200012

View details for PubMedID 9733604

Abstract

The authors describe their experience with the use of single-piece, tapered stent-grafts for the treatment of abdominal aortic or aortoiliac aneurysms.Single-piece, tapered stent-grafts were placed in 15 patients for the treatment of abdominal aortic aneurysms with small distal necks (n = 13), and aortoiliac aneurysms (n = 2). There were 13 men and two women who ranged in age from 59 to 83 years (mean, 71 years). Usual open surgery was considered high risk in all patients because of comorbid medical conditions. The stent-grafts were made of Z stents covered with polytetrafluoroethylene (PTFE). Additional stent-grafts needed to treat perigraft leaks were made of Z stents covered with woven polyester (n = 5), Wallstents covered with PTFE (n = 2), Z stents covered with PTFE (n = 1), and a PTFE-covered Palmaz stent (n = 1). After stent-graft placement, the contralateral iliac artery was occluded by a blocking device composed of either a PTFE-covered Palmaz (n = 1) or Z stent (n = 13), and a femoral-femoral bypass was created.After placement of the stent-grafts, immediate perigraft leaks were observed in eight patients (53%). These were at the proximal (n = 5) or the distal end (n = 3). All, except one, were treated successfully with additional stent-grafts. The one failure was in a patient who developed aortic rupture after balloon dilation, requiring open surgical repair. Second procedures were required in four patients (27%), including three leaks treated successfully with coil embolization and/or a back-up stent-graft, and one stent-graft migration and thrombosis treated by thrombolysis and placement of an additional stent-graft. One patient died of respiratory failure 23 days after placement of the stent-graft. The mean follow-up was 12 months (range, 4-26 months). On the last follow-up, the aneurysms in the 13 living patients remained thrombosed.Treatment of aortoiliac aneurysms with use of single-piece, tapered stent-grafts is feasible in selected patients. The morbidity and mortality rates compare favorably with those of the open surgical procedures in a high-risk population. Further improvements in the technique and longer follow-up data are needed before this procedure can be recommended for the treatment of all aortoiliac aneurysms.

View details for Web of Science ID 000071543100006

View details for PubMedID 9468394

Abstract

Surgical treatment of abdominal aortic aneurysm (AAA) is being challenged by newer, minimally invasive therapies. Such new treatment strategies will need to prove themselves against concurrent results of standard operative AAA repair, within defined medical risk and aneurysm morphological categories. We review the natural history of AAAs, the medical risk levels for elective AAA repair, aneurysm morphology and its impact on operative mortality, the issue of high-risk patient treatment, and the current standard of care for AAAs based on single-center, multicenter, and population-based statistics. In good-risk patients, aneurysms > 5 cm in diameter are best treated by replacement with a prosthetic graft. Operative mortality should be < 5% 1-year survival > 90%. Aortic endograft techniques must meet or exceed these standards if they are to supplant standard surgical repair.

View details for Web of Science ID A1997XU68300002

View details for PubMedID 9291048

Abstract

The flow field inside a model of a polytetrafluorethylene (PTFE) canine artery end-to-side bypass graft was studied under steady flow conditions using laser-Doppler anemometry. The anatomically realistic in vitro model was constructed to incorporate the major geometric features of the in vivo canine anastomosis geometry, most notably a larger graft than host artery diameter. The velocity measurements at Reynolds number 208, based on the host artery diameter, show the flow field to be three dimensional in nature. The wall shear stress distribution, computed from the near-wall velocity gradients, reveals a relatively low wall shear stress region on the wall opposite to the graft near the stagnation point approximately one artery diameter in axial length at the midplane. This low wall shear stress region extends to the sidewalls, suture lines, and along the PTFE graft where its axial length at the midplane is more than two artery diameters. The velocity distribution inside the graft model presented here provides a data set well suited for validation of numerical solutions on a model of this type.

View details for Web of Science ID A1997XB15100008

View details for PubMedID 9168395

Abstract

To review the anatomic factors crucial to successful endoluminal abdominal aortic aneurysm (AAA) repair and propose an ideal endograft design for AAA exclusion.The anatomic features of critical importance to endovascular AAA exclusion comprise remote arterial access, proximal and distal fixation sites, AAA morphology, and arterial wall pathology. When designing an aortic endograft, the major components to consider are stent selection, graft material, and the delivery system. The ideal endograft design must be sufficiently versatile to treat a broad range of patients. To meet this requirement, the endograft should display a high degree of dimensional adaptability. A modular bifurcated endograft design permits intraoperative customization to tailor the device to each patient's anatomy and pathology.The modular stent-graft concept addresses many of the important factors in the evolution toward an ideal aortic endograft. Extensive testing will be needed to determine if the bifurcated stent-graft described here is the optimal design for effective AAA exclusion.

View details for Web of Science ID A1997XD11100011

View details for PubMedID 9185007

Abstract

In-vivo velocity profiles were recorded with a 20 MHz 80-channel pulsed Doppler ultrasound velocimeter in canine end-to-side ilio-femoral anastomotic grafts. The geometries were obtained from casts of the anastomotic region, and flow rates were measured with electromagnetic flow probes. Three cases reported here include a "standard" geometry, which was similar to previously studied in vitro models, a stenosed geometry, and a case with below average flow rate. Observed flow features include separation at the hood and toe, movement of the floor stagnation point, and skewed profiles in the proximal outflow segment. Out-of-plane curvature and lateral displacement of the anastomosis inlet appear to have a strong effect on the flow fields. In addition, compliance affects the instantaneous flow rates within the proximal and distal branches.

View details for Web of Science ID A1997WN86800005

View details for PubMedID 9083846

View details for Web of Science ID A1996VW82800002

View details for PubMedID 8959492

Abstract

Superior mesenteric blood flow in the fasting and postprandial state in humans can be measured accurately by cine phase-contrast (CPC) magnetic resonance (MR) imaging. Postprandial flow changes associated with mesenteric arterial occlusive disease (MAOD) are unknown.We used CPC MR imaging to measure fasting and postprandial blood flow in the superior mesenteric artery (SMA) and vein (SMV) in 22 patients (mean age, 69 years) with aortic occlusive disease and MAOD and compared the results with similar measurements in 8 younger, asymptomatic volunteers (mean age, 34 years). All 22 patients had stenosis or occlusion of the splanchnic or pelvic arteries demonstrated by contrast aortography; 19 were asymptomatic and 3 had symptoms of chronic mesenteric ischemia. Mean fasting blood flow was higher in patients (4.5 mL.kg-1.min-1) than in volunteers (2.3 mL.kg-1.min-1; P < .01). However, postprandial hyperemia (mean percentage change in SMV blood flow) was less in the asymptomatic (70%; P < .001) and symptomatic patients (29%; P < .01) than in the volunteers. Postprandial SMV flow was similar to SMA flow in the patients but was significantly greater than SMA flow in the volunteers (P < .005).Postprandial mesenteric hyperemia is reduced in older patients with MAOD. The role of aging alone has not been determined. Fasting and postprandial flow changes in these patients may predict the onset of chronic mesenteric ischemia.

View details for PubMedID 8901747

Abstract

Many surgeons advocate uniform performance of operative completion arteriography after leg bypass surgery to ensure technical success and to optimize short- and intermediate-term graft patency. To determine the impact of this practice on the outcome of reversed-vein bypass surgery and associated patient charges, we reviewed our series of consecutive nonemergent leg bypass procedures. Ninety-three infrainguinal bypass procedures were performed in 80 patients (76 men and 4 women) from September 1991 to August 1994. The patients' average age was 67 years (range, 30 to 92 years). Follow-up (mean, 113.1 months; range, 1 to 36 months) was available on 91 grafts (97%). Indications for surgery included limb salvage in 75 cases, claudication in 12 cases, and popliteal aneurysm exclusion in 6 cases. All patients survived surgery. Primary graft patency rates as determined by life-table analysis were 87%, 81%, 78%, and 78% at 6 months and at 1, 2, and 3 years, respectively. Limb-salvage rates were 95%, 91%, 87% and 87% at the same intervals. Bypass procedures were divided into two groups. The 25 grafts in group 1 were evaluated with inspection, continuous-wave Doppler insonation, and routine completion arteriography. The 68 grafts in group 2 were evaluated by inspection and insonation alone. Fourteen grafts occluded after surgery (average, 5 months; range, 1 to 12 months), five in group 1 and nine in group 2. The likelihood of graft occlusion was similar in both groups (p = 0.42). The optimal method of confirming technical adequacy after bypass surgery in the clinically satisfactory graft remains uncertain. Charges for completion arteriography at our institution average $700, including 15 minutes of additional operative time. In our experience, these charges do not appear to be justified by improved short- or intermediate-term graft patency rates in reversed-vein grafts when completion arteriography is performed.

View details for Web of Science ID A1996UJ12600016

View details for PubMedID 8627900

Abstract

Hypertension is a known clinical risk factor for atherosclerosis. In experimental atherosclerosis, monocyte adhesion to the endothelial surface is enhanced and is considered to be an important early stage in plaque formation. We tested the hypothesis that hypertension enhances monocyte adhesion in experimental atherosclerosis.Twenty-two New Zealand White rabbits were fed an atherogenic diet for 3 weeks to induce plaque formation. Aortic coarctation was created in eight rabbits by wrapping a Dacron band around the midportion of the descending thoracic aorta (stenosis group), whereas six rabbits underwent banding without aortic constriction (no stenosis group). Eight rabbits served as nonoperated controls. Monocyte binding to the aortic endothelial surface was counted with epifluorescent microscopy on standard aortic segments proximal and distal to the band. Immunohistochemistry was performed for the following antibodies: VCAM-1, RAM11, CD11b, and factor VIII.Mean blood pressure was 89 +/- 3 mm Hg in the aorta proximal to the stenosis, compared with 64 +/- 4 mm Hg in the no stenosis group and 74 +/- 3 mm Hg in the control group (p < 0.01). The mean aortic blood pressure gradient across the stenosis was 16 +/- 2 mm Hg in the stenosis group, whereas the aortic blood pressure gradient was 0.2 +/- 0.6 mm Hg in the no stenosis group and -0.3 +/- 0.4 mm Hg in the control group (p < 0.001). Monocyte adhesion to the aortic endothelial surface proximal to the stenosis was increased twofold compared with adhesion to the aorta distal to the stenosis and compared with the proximal aorta in the control group (p < 0.02). The proximal-to-distal aortic ratio of monocyte binding was enhanced in the stenosis group (2.2) compared with the no stenosis (0.76) and control (0.83) groups (p < 0.01). The intima area of the aorta proximal to the stenosis was significantly increased compared with the proximal aortas in the no stenosis and control groups (p < 0.01). RAM11, CD11b, and endothelial VCAM-1 expression were enhanced in the hypertensive region proximal to the stenosis.In the hypertensive region in the aorta proximal to the stenosis, monocyte adhesion and endothelial VCAM-1 expression were increased, with intimal thickening and accumulation of macrophages. These findings suggest that hypertension may promote atherosclerotic plaque formation by enhancing monocyte adhesion.

View details for Web of Science ID A1996UJ12600010

View details for PubMedID 8627894

Abstract

Carotid endarterectomy has been firmly established as the gold standard of therapy for symptomatic and asymptomatic patients with severe carotid stenosis, provided surgical complication rates are within prescribed limits. The procedure-related risk of stroke/death should be < 3% in asymptomatic patients and < 6% in symptomatic patients. New investigational therapies such as balloon angioplasty and stenting for carotid stenosis should be evaluated against the same standard.

View details for Web of Science ID A1996TU63500006

View details for PubMedID 8798120

View details for PubMedID 15858751

View details for Web of Science ID A1995UQ43600025

View details for PubMedID 8850680

Abstract

Magnetic resonance (MR) angiography and spiral CT angiography are promising new imaging modalities for evaluating patients with lower extremity arterial occlusive disease. Both techniques are less invasive than conventional angiography, and MR angiography has the additional advantages of not requiring iodinated contrast media or ionizing radiation. The basic principles of MR angiography and spiral CT angiography are reviewed with an emphasis on three-dimensional display techniques. This is followed by a discussion of their clinical applicability toward the diagnosis and treatment planning of lower extremity arterial occlusive disease.

View details for Web of Science ID A1995RN07700007

View details for PubMedID 7638708

Abstract

The artery wall adapts to changes in wall tension and wall shear stress by means of enlargement and changes in both thickness and composition. The intima may participate in these changes, and these compensatory adaptive-reactive modifications continue in the presence of atherogenesis. Further understanding of the interaction of the evolving plaque with the artery wall and the associated effects of the physical forces associated with the circulation should provide new insights into the nature of plaque instability and into the outcome of direct interventions.

View details for Web of Science ID A1995RN07700002

View details for PubMedID 7638703

Abstract

An automated three-dimensional particle tracking technique has been developed to study particle motion in modeled flow fields. A high speed video recording system. Kodak Ektapro 1000, with two cameras arranged relatively orthogonally is used for this technique. The particle tracking data are compared to theoretical Poiseuille flow and to laser Doppler data from an axisymmetric stenosis model. The particle tracking data are in good agreement with both theoretical and laser Doppler data, and at least 79 percent of the particle paths were determined successfully. Fluid dynamic properties derived by this technique are: 3-D particle paths, velocity, and particle residence time.

View details for Web of Science ID A1995RK69400006

View details for PubMedID 7666658

Abstract

Clinically significant atherosclerosis in the human aorta is most common in the infrarenal segment. This study was initiated to test the hypothesis that flowfield properties are closely related to the localization of plaques in this segment of the arterial system. Wall shear stress was calculated from magnetic resonance velocity measurements of pulsatile flow in an anatomically accurate model of the human abdominal aorta. The wall shear stress values were compared with intimal thickening from 15 post-mortem aortas measured by quantitative morphometry of histological cross sections obtained at standard locations. Wall shear stress oscillated in direction throughout most of the infrarenal aorta, most prominently in the distal region. The time-averaged mean wall shear stress (-1.7 to 1.4 dyn/cm2) was lowest near the posterior wall in this region. These hemodynamic parameters coincided with the locations of maximal intimal thickening. Statistical correlation between oscillatory shear and intimal thickness yielded r = 0.79, P < 0.00001. Low mean shear stresses correlated nearly as well (r = -0.75, P < 0.00005). Comparison of our data with surface maps of Sudan Red staining and early lesions as reported by others revealed similar conclusions. In contrast, pulse and maximum shear stresses did not correlate with plaque localization as has been shown for other sites of selective involvement by atherosclerosis (r < 0.345). Simulated exercise conditions markedly changed the magnitude and pattern of wall shear stress in the distal abdominal aorta. These results demonstrate that in the infrarenal aorta, regions of low mean and oscillating wall shear stresses are predisposed to the development of plaque while regions of relatively high wall shear stress tend to be spared.

View details for Web of Science ID A1994PQ69500008

View details for PubMedID 7848371

Abstract

Arteries enlarge where intimal plaques form, tending to preserve lumen cross sectional area but causing an increase in mural tangential tension due to the increase in radius. To characterize the compensatory enlargement process at the carotid bifurcation and to evaluate the possible contribution of intima thickening to mural tensile support during the enlarging process, we assessed the relationships among intimal thickening, artery size and estimated tensile stress at 9 sequential axial levels in 42 human carotid bifurcations obtained during post-mortem examinations of 36 adults with no clinical or anatomical evidence of cerebrovascular disease. Right and left bifurcations were available for 6 patients. The arteries were fixed under conditions of controlled pressure distention and histologic sections were prepared at 0.5 cm axial intervals. We determined vessel radius (r), intima thickness (IT), media thickness (MT), intima area (IA), lumen area (LuA) and the area encompassed by the internal elastic lamina (IELA), i.e. the lumen area if there were no intimal thickening. Although IT, IA and r were greatest in the proximal sinus region, there was a highly significant linear relationship between IA and IELA at each axial level; correlation coefficients ranged from 0.64 to 0.97 with P < 0.001 at each level. Stenosis (IA/IELA x 100) ranged from 10.8 +/- 8.0% at the common carotid level immediately proximal to the bifurcation angle to 22.3 +/- 17.9% at the level immediately distal to the angle, but LuA remained nearly constant at each level regardless of IA.(ABSTRACT TRUNCATED AT 250 WORDS)

View details for Web of Science ID A1994NT18300003

View details for PubMedID 7980691

Abstract

The spatial distribution of intimal thickening was determined for each of 42 carotid bifurcations removed at autopsy from patients with no clinical or anatomic evidence of cerebrovascular disease. Both right and left specimens were available for six of the individuals. Each bifurcation was removed intact and included a 1.5-2.9-cm length of the common carotid artery and a 1.5-2.5-cm length of the internal carotid artery. The specimens were restored to in situ length, fixed under conditions of controlled-pressure perfusion at 100 mmHg, filled with a radio-opaque mixture, radiographed and sectioned at 0.5-cm intervals. Computer assisted contour tracing of projected images of histologic sections was used to determine intimal thickness, intimal cross sectional area and lumen area within each of eight equal 45 degrees polar sectors with 0 degree indexed at the flow divider, 90 degrees at the outside wall, 180 degrees opposite the flow divider and 270 degrees at the inner side wall. Intima occupied 0.9-42% of the area encompassed by the internal elastic lamina, i.e. the potential lumen area if no intimal thickening were present, but there was no lumen narrowing on lateral X-ray projections. Intimal thickening was eccentric at each level of section but the circumferential location of maximum intimal thickness (MIT) shifted in a continuous helix from level to level. At the common carotid artery level 1.0 cm proximal to the bifurcation, MIT tended to be at the flow-divider side at 15 +/- 59 degrees. Immediately proximal to the flow divider, MIT was at the lateral side wall. In the mid-sinus region of the internal carotid artery MIT was opposite the flow divider at 179 +/- 64 degrees. At the distal internal carotid just beyond the sinus, MIT was at the inner side wall. The distal internal carotid was minimally involved or free of intimal thickening. Comparison of right and left bifurcations revealed that the helical spatial distribution of MIT was in mirror-image symmetry for the two sides. The findings correspond closely with previous demonstrations of a helical flow pattern in the region of the bifurcation. Although locations of MIT just proximal and just distal to the bifurcation are similar and tend to be at the 'far wall', individual differences in the shifts of MIT with axial location should be taken into account when sites of interrogation by non-invasive clinical methods are selected for detection of intimal thickening.

View details for Web of Science ID A1994NT18300002

View details for PubMedID 7980690

Abstract

Human aortic atherosclerosis is predominantly localized to the infrarenal aorta where flow is bidirectional and wall shear stress oscillates. Similar flow patterns have been related to carotid atherosclerosis. The thoracic aorta is usually spared, where flow and shear stress are unidirectional. We hypothesized that because heart rate and systemic blood pressure modulate flow velocity and shear stress oscillation, both these hemodynamic forces may enhance aortoiliac atherogenesis.Eighteen male cynomolgus monkeys were fed an atherogenic diet for 6 months (mean serum cholesterol = 535 +/- 35 mg/dl). Heart rate was determined with 24-hour electrocardiographic telemetry at monthly intervals and blood pressure was measured by direct arterial cannulation. The product of mean heart rate and mean blood pressure was used to define hemodynamic stress for each animal. Atherosclerotic lesion formation at three standard thoracic aortic sites was quantitatively compared with lesion formation at five standard infrarenal aortoiliac locations with computer-assisted morphometry.There was significantly more plaque in the aortoiliac segment than in the thoracic aorta (12.4% +/- 9.0% vs. 6.4% +/- 4.5% area stenosis, p = 0.02). No correlation was found between the degree of serum lipid elevations and lesion formation in either aortic location. Mean heart rate was 113 +/- 18 beats/min (87 to 163 beats/min) and mean blood pressure was 85 +/- 19 mm/Hg (62 to 130 mm Hg). Heart rate and blood pressure alone were not significantly related to lesion formation. A significant correlation was, however, found between hemodynamic stress and maximum lesion thickness (r = 0.47, p < 0.05) in the aortoiliac region but not in the thoracic aorta (r = 0.19, p > 0.10).This study demonstrates that heart rate and blood pressure exert a mutually potentiating effect on aortoiliac atherosclerosis but not on thoracic aortic atherosclerosis. Regional differences in aortic atherosclerosis may therefore be attributable to the interaction between these hemodynamic forces and the local flow patterns specific to each aortic location. Additional investigation of these hemodynamic factors in relation to human aortic atherosclerosis is warranted.

View details for Web of Science ID A1994NA32900005

View details for PubMedID 8126855

Abstract

To investigate the role of a compliant wall to the near wall hemodynamic flowfield, two models of the carotid bifurcation were constructed. Both were of identical internal geometries, however, one was made of compliant material which produced approximately the same degree of wall motion as that occurring in vivo while the other one was rigid. The inner geometries were formed from the same mold so that the configurations are directly comparable. Each model was placed in a pulsatile flow system that produced a physiologic flow waveform. Velocity was measured with a single component Laser system and wall shear rate was estimated from near wall data. Wall motion in the compliant model was measured by a wall motion transducer and the maximum diameter change varied between 4-7 percent in the model with the greatest change at the axis intersection. The mean shear stress in the compliant model was observed to be smaller by about 30 percent at most locations. The variation in peak shear stress was greater and occasionally reached as much as 100 percent with the compliant model consistently having smaller positive and negative peaks. The separation point was seen to move further upstream in the compliant cast. The modified flowfield in the presence of a compliant wall can then be important in the hemodynamic theory of atherogenesis.

View details for Web of Science ID A1994MZ75000013

View details for PubMedID 8189720

Abstract

Fluid dynamics research over the past twenty years has contributed immensely to our knowledge of atherosclerosis. The ability to detect localized atherosclerotic plaques using noninvasive ultrasonic methods was advanced significantly by investigations into the nature and occurrence of velocity disturbances created by arterial stenoses, and diagnosis of carotid bifurcation disease using a combination of ultrasonic imaging and Doppler measurement of blood velocity is now quite routine. Since atherosclerotic plaques tend to be localized at sites of branching and artery curvature and since these locations would be expected to harbor complex flow patterns, investigators postulated that fluid dynamics might play an initiating role in atherogenesis. Several fluid dynamic variables were proposed as initiating factors. Investigations were undertaken during the 1980s in which fluid dynamic model experiments with physiologic geometries and flow conditions were employed to simulate arterial flows and in which morphometric mapping of intimal thickness was performed in human arteries. Correlations between fluid dynamic variables and intimal thickness revealed that atherosclerotic plaques tended to occur at sites of low and oscillating wall shear stress; and these observations were reinforced by studies in a monkey model of atherosclerosis. Concomitantly, it was realized that arteries adapt their diameters so as to maintain wall shear stress in a narrow range of values around 15 dynes/cm2, findings which were based both on observations of normal arteries and on animal studies in which flow rates were manipulated and arterial diameter adaptation was measured.(ABSTRACT TRUNCATED AT 250 WORDS)

View details for PubMedID 8302046

Abstract

Cynomolgus monkeys were fed an atherogenic diet for 6 months following surgically produced high-grade (n = 10) or mild (n = 16) mid-thoracic aortic coarctation. A diet-control (DC) group (n = 13) was fed the diet without coarctation. High-grade coarctation (HGC) resulted in 74.1% +/- 8.3% stenosis by aortography prior to sacrifice and was associated with systolic brachial blood pressures of 143.3 +/- 26.0 mmHg and gradients across the stenoses of 36.8 +/- 23.6 mmHg. Mild coarctation (MC) resulted in stenoses of 50.9% +/- 12.9%, brachial systolic pressures of 119.4 +/- 25.7 and gradients of 12.5 +/- 15.2 mm Hg (P < 0.01, P = 0.03 and P < 0.005, respectively, compared with HGC). When total plaque cross-sectional area exceeded 0.8 mm2, the entire arterial circumference was usually involved. HGC resulted in complete sparing or minimal plaque formation in sections distal to the stenoses compared with proximal sections (P < 0.001). There were no significant differences between MC and DC animals in plaque location or size. Matrix content increased with plaque area regardless of degree of stenosis or sampling level (P < 0.01), but lesions with more than 75% matrix content were more numerous in distal than in proximal sections despite their smaller size. The number of plaques with greater than 75% matrix content was increased proximal to HGC (P < 0.04). Thus, distal location and plaque size were independent determinants of plaque matrix content and matrix content was increased proximal to HGC regardless of plaque size. Attempts to evaluate effects of various regimens and interventions on plaque composition need to take location and plaque size, as well as blood pressure differences, into account.

View details for Web of Science ID A1993LX65600004

View details for PubMedID 8257451

Abstract

CT imaging of traumatic aortic rupture has been both advocated and disparaged in the current literature as a reliable diagnostic modality. In a retrospective review of blunt chest trauma patients at our institution evaluated by both thoracic CT and arteriography, we found a 17% false negative rate and a 39% false positive rate. Although we feel CT is not sufficiently sensitive at present to evaluate traumatic rupture of the aorta directly, it is an invaluable adjunctive imaging modality for stable blunt chest trauma patients with equivocal chest radiographs or arteriograms.

View details for PubMedID 8518129

Abstract

Flow behavior in models of end-to-side vascular graft anastomoses was studied under steady and pulsatile flow conditions. Models were constructed to simulate geometries employed in experimental studies on intimal thickening in a canine model. Reynolds numbers, division of flow in the outflow tracts and the pulsatile waveform employed were taken from measurements obtained in the canine model. Flows in the scaled-up, transparent models were visualized with white, neutrally buoyant particles which were photographed under laser illumination and also recorded on video tape under bright incandescent light. Strong, three-dimensional helical patterns which formed in the anastomotic junction were prominent features of the flow fields. Regions of low wall shear, oscillatory wall shear and long particle residence time were identified from the flow visualization experiments. Comparisons with the limited qualitative data available on intimal thickening in vascular graft anastomoses suggest a relation between localization of vascular intimal thickening and those surfaces experiencing low shear and long particle residence time.

View details for Web of Science ID A1993KQ01400015

View details for PubMedID 8445887

Abstract

Arteries adjust to alterations in wall shear stress or tensile stress by changes in diameter, wall thickness, structure and composition. The intima participates in these adaptive reactions, particularly when changes in mechanical stresses are imposed after physiologic stress levels have been established during growth. Decreased wall shear stress due to decreased flow, flow separation or complex flow patterns, or increases in tensile stress due to increases in pressure or radius stimulate non-atherosclerotic intimal proliferation. Intimal fibrocellular hypertrophy (IFH), in the form of compact fibrocellular layers resembling the media, stabilizes when the lumen diameter is reduced sufficiently or wall thickness is increased sufficiently to restore baseline wall shear or tensile stress. Reactive-adaptive intimal proliferation is not necessarily self-limiting and may continue in the form of intimal hyperplasia (IH) which is relatively matrix-free and poorly organized. If mural and intimal changes do not result in restoration of baseline wall shear and tensile stress, IH may proceed to further narrowing and stenosis. Identification of the cellular and molecular mechanisms which underly the responses which link flow to diameter, diameter and pressure to mural restructuring, and mural restructuring to intimal thickening should provide new insights into the nature of vessel adaptations in the absence or presence of atherogenesis.

View details for PubMedID 8323881

Abstract

We have characterized plaque localization, the extent of compensatory artery enlargement, and the effect of heart rate in experimental atherosclerosis at the carotid bifurcation of the cynomolgus monkey. We altered heart rate by sino-atrial node ablation (SNA) and then fed the animals an atherogenic diet for 6 months. Heart rate was measured at four time points by 24-hour telemetry. Of nine animals with SNA, heart rate was reduced significantly in six (from 148 +/- 11 to 103 +/- 20 beats/min, p < 0.001) and was unchanged in three. Sham-operated monkeys had no significant change in heart rate. On the basis of comparison with the preoperative mean for all 17 animals (136 +/- 22 beats/min), animals were separated into a low-heart-rate (LHR) group (111 +/- 16 beats/min, n = 12) and a high-heart-rate (HHR) group (150 +/- 16 beats/min, n = 5). Blood pressure, serum cholesterol level, and body weight did not differ for the two groups. As in the human, plaques formed predominantly in the proximal portion of the internal carotid artery at the lateral wall opposite the flow divider. Plaque cross-sectional area increased progressively from the relatively uninvolved, adjacent common carotid artery to the mid-sinus region of the internal carotid artery and decreased from the mid-sinus region to the internal carotid artery beyond the sinus. Plaque distribution was the same for the LHR and HHR groups, but lesion area and percent stenosis were greater for the HHR group than for the LHR animals (2.01 +/- 1.19 compared with 0.76 +/- 0.42 mm2 for lesion area [p < 0.02] and 30.7 +/- 4.4% compared with 15.2 +/- 7.3% for stenosis [p < 0.002]).(ABSTRACT TRUNCATED AT 250 WORDS)

View details for Web of Science ID A1992JX30200002

View details for PubMedID 1420083

Abstract

Autologous saphenous veins are considered the best arterial substitute for lower extremity revascularization in infected fields. The search continues for a vascular conduit in instances when an autologous biologic grafting is not feasible. Herein we report our experience with eight patients in whom cryopreserved saphenous vein allogenic homografts were used in 10 lower extremity arterial reconstructions for limb salvage with coexisting infection. Six patients with eight prosthetic grafts including four femoropopliteal, two femorotibial, a femorofemoral, and a femoroperoneal graft required complete or partial graft excision as a result of overt infection. The two remaining patients included one with an infected femoral pseudoaneurysm and another with extensive chemical burns. All cryopreserved saphenous vein allogenic homografts were of identical match to the ABO/Rh blood groupings of the recipient patients. No immunosuppressive drugs were administered after operation. Mean follow-up was 9.5 months (range, 6.0 to 14.0 months). One patient died 5 weeks after operation with a patent graft. Two grafts occluded during follow-up; in one graft, patency was restored with thrombectomy alone. The remaining seven arterial reconstructions continue to be patent with no evidence of aneurysmal dilation with complete eradication of the primary infection. These preliminary findings suggest that cryopreserved saphenous vein allogenic homografts can serve as interim conduits for lower extremity arterial reconstruction to preserve limb viability when autogenous conduits are unsatisfactory or unavailable. Further definitive reconstruction may thereafter be necessary once sepsis is eradicated and sufficient wound healing is achieved.

View details for Web of Science ID A1992HH07300007

View details for PubMedID 1538509

Abstract

To assess the effect of hypertension on diet-induced coronary artery plaques after a return to a nonatherogenic diet, 10 cynomolgus monkeys were fed an induction regimen containing 2% cholesterol and 25% peanut oil for 6 months and then were subjected to midthoracic aortic coarctation to induce hypertension. The animals were then fed a nonatherogenic "prudent" ration for 6 additional months (hypertension-regression group). Twelve additional monkeys were fed the atherogenic diet for 6 months; six were killed (lesion-induction control group) and six were changed to the prudent diet for 6 additional months without coarctation (normotension-regression control group). At the end of the induction period, cholesterol levels averaged 744 +/- 178 mg/dl for the 22 animals and were similar for the three groups throughout the induction period. For the animals restored to the nonatherogenic diet (hypertension-regression and normotension-regression groups), serum cholesterol levels fell to 486 +/- 252 mg/dl at 1 month, to 341 +/- 162 mg/dl at 2 months, and to 234 +/- 78 mg/dl at 6 months. There was no significant difference between the hypertensive and normotensive animals. Six months after coarctation, blood pressure proximal to the coarctations for the hypertension-regression group ranged from 100/60 to 220/145 mm Hg with a mean of 166/103 +/- 36/28 mm Hg. Cross-sectional area of coronary plaques was somewhat lower for the normotension-regression control group compared with the lesion-induction control group, but the difference was not significant. Plaque area was, however, markedly greater in the hypertension-regression group than in either the lesion-induction or the normotension-regression groups (p less than 0.05 for each) despite progressive reduction in hyperlipidemia.(ABSTRACT TRUNCATED AT 250 WORDS)

View details for Web of Science ID A1991GB06400001

View details for PubMedID 1885220

Abstract

Ten patients with true aneurysmal disease of the hand and forearm vessels were treated at our institution between 1981 and 1990. Pseudoaneurysms resulting from penetrating trauma or mycotic aneurysms were specifically excluded. Eight patients were male, two were female; mean patient age was 38 years (range 26 to 72 years). A history of repetitive occupational or recreational trauma was elicited in five patients. All patients presented with painful masses or neurologic symptoms due to nerve compression. Ischemic changes were evident in five patients due to thrombosis or distal embolization. Arteriography and transcutaneous Doppler ultrasound aided in documentation of flow characteristics and planning for operative intervention. Three patients underwent excision and ligation once collateral flow was demonstrated to be adequate and reconstruction was not felt to be feasible. Seven patients underwent resection with vein graft reconstruction. Immediate postoperative and interval patency rates were 100%. No digital amputations were required even in those patients presenting with severe distal ischemia.

View details for PubMedID 2064922

View details for Web of Science ID A1991FL78000032

View details for PubMedID 2027221

View details for Web of Science ID A1991FF48000023

View details for PubMedID 2010937

View details for PubMedID 2090552

Abstract

If endothelial injury plays a prominent role in early atherogenesis, the plasma levels of von Willebrand factor (VWF), which is made within and normally released from endothelial cells, might be expected to rise as a marker of the cellular damage. To evaluate this hypothesis, we measured plasma VWF (as VIIIR:Ag), factor VIII:C, and serum lipids serially up to 37 weeks in 29 adult male cynomolgus monkeys on an atherogenic diet. Factor VIII:C peaked at 113% above baseline by week 10 (p less than 0.0001), then fell and remained 53% below baseline (p less than 0.04) during weeks 20 to 37. However, the overall rise in VWF was not significant. In contrast, serum cholesterol continued to rise after week 21. Serum phospholipids (PL), triglycerides (TG), and free fatty acids (FFA) showed a temporal pattern similar to VIII:C. Significant positive correlations with VIII:C were noted for PL (r = 0.59, p = 0.0001) and TG (r = 0.36, p = 0.0096). At autopsy, small to moderately advanced atherosclerotic lesions were distributed throughout the aortas of the majority of the animals. We conclude that changes in plasma VIIIR:Ag do not correlate with atherogenesis in this model. However, the similar course of VIII:C, TG, and PL suggests that these substances may be involved and perhaps interrelated early in atherogenesis.

View details for Web of Science ID A1990EJ21600016

View details for PubMedID 2123089

View details for Web of Science ID A1990CZ23300008

View details for PubMedID 2319823

View details for Web of Science ID A1989CC98100016

View details for PubMedID 2585660

Abstract

To assess the extent to which endothelial cell (EC) structure is modified by hyperlipidemia and by the formation of intimal plaques, we undertook a quantitative ultrastructural study of aortic EC of cynomolgus monkeys after 3 or 6 months on an atherogenic diet. We compared EC in lesion-free areas (LFA) with EC overlying focal discrete foam cell accumulations (FDA) or covering multilayered confluent plaques (MCP). There was a 15% increase in cross-sectional lumen surface profile length over FDA or MCP compared to LFA (p less than 0.005) corresponding to the bulging contours of immediately underlying foam cells. There was, however, no increase in the number of EC per unit of surface area (26.2 +/- 4.47 per 10(4) mm2 for LFA and 26.0 +/- 4.22 for FDA) or, on cross-section, per 100 microns length of underlying internal elastic lamina (8.79 +/- 2.42 for LFA, 8.26 +/- 2.01 for MCP). Nor did the number of surrounding cells contacted by each cell over LFA or MCP differ from normolipemic controls (6.56 +/- 0.85 for LFA and 5.58 +/- 0.86 for MCP). Most ECs were markedly attenuated over lesions, and while the extent and complexity of lateral contact regions between adjacent EC was diminished, the number and complexity of basilar projections was greatly increased. These structures extended among the intimal foam cells to insert on the internal elastic lamina or on intimal matrix fibers, resulting in a 2.7-fold increase in the length of the abluminal portion of the EC profile. The perimeter of the transverse EC profiles was thereby increased from 41.4 +/- 2.12 microns in LFA to 82.2 +/- 5.21 microns over MCP (p less than 0.0001). Polarization of EC in the direction of flow diminished as lesions developed. The ratio of length to width, as well as the standard deviation of the ratio, decreased from 3.51 +/- 3.92 in LFA to 2.35 +/- 0.25 over MCP, due mainly to increases in the proportion of the cell perimeter exposed to the lumen. Lesion localization bore no relationship to the orientation of EC in corresponding locations in the normolipemic controls or in LFA immediately adjacent to plaques. Organelles of EC in hyperlipidemic animals showed features suggestive of increased metabolic activity in all regions, and stress filaments were increased in the EC attenuated over lesions. There was no evidence of EC degeneration, necrosis, or sloughing regardless of lesion location, size, or complexity.

View details for Web of Science ID A1989CC03700014

View details for PubMedID 2590066

Abstract

This retrospective study compared the results of percutaneous transluminal angioplasty (PTA) with those of infrainguinal bypass procedures in patients with critical arterial ischemia to determine which procedure had superior patency, limb salvage, and durability. The records of 54 patients who underwent 54 PTAs and 56 patients who underwent 63 infrainguinal bypasses (29 femoropopliteal and 34 femorodistal) from 1981 to 1987 were reviewed. In each patient PTA or bypass was the initial vascular procedure. Patients in both groups were comparable with respect to age, sex, and the presence of diabetes, hypertension, obesity, hypercholesterolemia, and smoking. Mean follow-up was 40 months (4 to 88 months) for the PTA group and 28 months (6 to 78 months) for the surgery group. Thirty-nine of the 54 patients (72%) were initially improved after PTA, whereas 15 patients (28%) showed no improvement. During follow-up, 20 initially successful PTAs reoccluded. Thirty-two of 54 patients (59%) underwent subsequent procedures, which included repeat PTA (10) and distal bypass (14). Patency determined by noninvasive Doppler studies was 18% at 2 years. Limb salvage, which included such secondary procedures, was 78%. Two-year patency for femoropopliteal bypasses was 68% with a limb salvage of 90%. Femorodistal bypasses had a 2-year patency of 47% and a limb salvage of 74%. No perioperative deaths occurred. Twenty-one of the 63 patients (33%) had subsequent procedures, which included thrombectomy (5) and bypass revision (9). In patients treated for limb-threatening ischemia the 2-year patency after femoropopliteal bypass (68%) or femorodistal bypass (47%) is significantly better than that from PTA (18%, p less than 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)

View details for Web of Science ID A1989U761300012

View details for PubMedID 2524606

Abstract

To identify microanatomic and chemical features that may mark the transition from asymptomatic to symptomatic atherosclerotic carotid lesions, we evaluated 62 carotid artery bifurcation plaques including 45 high-grade stenoses removed at endarterectomy and 17 nonstenotic plaques recovered at autopsy. Morphologic features were evaluated on multiple-interval histologic sections and were graded for the presence of hemorrhage, ulceration, thrombosis, lumen surface irregularity, and calcification. Plaque hemorrhage, recent and remote, was found in most of the specimens, and did not discriminate between symptomatic and asymptomatic stenotic plaques. High-grade carotid stenotic plaques were associated with a significantly higher incidence of ulceration (53%), thrombosis (49%), and lumen irregularity (78%) when compared to nonstenotic asymptomatic plaques (6%, 0%, and 17%, respectively; p less than 0.01). Although these features were more prominent in lesions that produced symptoms, they were present in 80% of the stenotic bifurcations, and did not distinguish between symptomatic and asymptomatic endarterectomy plaques. No significant differences were found between symptomatic and asymptomatic high-grade lesions with respect to collagen, DNA, total cholesterol, fibrinogen, lipase, elastase, or collagenase content. We conclude that intraplaque hemorrhage is commonly seen in carotid plaques even without severe stenosis, and it does not appear to be a dominant determinant of symptoms. Ulceration and surface thrombi that may lead to cerebral embolization are prominent features in markedly stenotic plaques even when symptoms are absent. The disruptive processes that underlie plaque instability appear to be closely associated with plaque size and stenosis rather than plaque composition.

View details for Web of Science ID A1989T336900004

View details for PubMedID 2537432

Abstract

Specific hemodynamic factors have been shown to be associated with atherosclerotic plaque localization at the human carotid bifurcation. Flow field characteristics may also determine plaque distribution in the abdominal aorta. We therefore characterized flow patterns in a glass model abdominal aorta that included its major branches under conditions of steady flow. Outflow resistances of the celiac, superior mesenteric, renal, inferior mesenteric, and iliac arteries were varied to produce flow distributions consistent with rest, the postprandial state, and vigorous lower limb exercise. Flow patterns were visualized with three colors of dye injected simultaneously through capillary tubes at selected locations and recorded as still photographs and by cinephotography on videotapes. Under resting conditions a large region of flow separation and stagnation occurred at the posterior wall of the aorta directly opposite the orifices of the superior and inferior mesenteric arteries. Similar separation regions were observed during the simulated postprandial state but diminished markedly when distal outflow was increased to levels consistent with exercise. In the highly susceptible infrarenal aortic segment, beginning about 2 cm below the renal artery orifices, multiple secondary flow patterns with three to four counterrotating vortex formations were observed under both resting and postprandial conditions but disappeared in the exercise state. Secondary flow patterns were not noted in the suprarenal abdominal aorta, which is usually relatively spared. Such features have been related to plaque localization elsewhere, and the disappearance of these patterns with increased flow velocity during exercise is consistent with the previously noted protective effect of unidirectional laminar high-flow states. The beneficial effects of physical fitness programs may be related in part to these hemodynamic modifications.

View details for Web of Science ID A1989T336900016

View details for PubMedID 2918626

View details for Web of Science ID A1989R767700030

View details for PubMedID 2521256

Abstract

Arteries respond to long-term changes in flow rate by alterations in caliber that tend to restore wall shear stress to normal baseline levels. Changes in radius, pressure, or geometric configuration elicit changes in structure and composition of the media in keeping with the altered level and distribution of tensile stresses. Similar stabilizing adaptations occur in the presence of conditions that induce the formation of atherosclerotic plaques, but the ultimate effectiveness of these reactions is variable. Several recent experiments provide information on the possible effects of hyperlipidemia on the smooth muscle cell (SMC) response to normal or increased levels of mechanical stress: (a) Normolipemic serum increases collagen synthesis by SMCs grown on purified elastin membranes compared to synthesis in serum-free medium, but synthesis is not further enhanced by cyclic stretching of the cells. Collagen production increase is less marked in hyperlipemic serum, but cyclic stretching raises synthesis to a degree comparable to that noted for serum-free medium. (b) The increase in artery diameter in response to increased flow rate and the elaboration of media components in relation to the increase in diameter are not hampered by hyperlipidemia. (c) The compensatory enlargement of arteries in response to plaque formation is not prevented by hyperlipidemia even in the presence of hypertension. (d) The healing of a transmural necrotizing injury of the media is, however, retarded and incomplete in the presence of hyperlipidemia. These findings indicate that hyperlipidemia per se does not necessarily interfere with the SMC response to mechanical stimuli. The usual adaptive reactions remain intact.(ABSTRACT TRUNCATED AT 250 WORDS)

View details for Web of Science ID A1989AT68400019

View details for PubMedID 2478833

Abstract

A case illustrating fracture and translocation of a Kim-Ray Greenfield filter strut due to intraoperative manipulation of the filter during cholecystectomy is presented. Awareness of this previously unreported complication is essential in preventing its occurrence.

View details for Web of Science ID A1989T459800026

View details for PubMedID 2925771

Abstract

The evaluation of clinical reports on vascular disease is often made difficult by variations in descriptive terms, clinical classification, and outcome criteria. In 1983 the Joint Council of the Society for Vascular Surgery and the North American Chapter of the International Society for Cardiovascular Surgery created the Ad Hoc Committee on Reporting Standards to address these problems and recommend solutions. Some general problems were addressed in the initial report dealing with lower extremity ischemia. This article concerns clinical standards for reports dealing with cerebrovascular disease, suggests a scheme for clinical classification, and recommends standardized reporting practices for grading risk factors, angiographic and other diagnostic findings, and the results and complications of therapeutic intervention.

View details for Web of Science ID A1988R284900012

View details for PubMedID 3193551

Abstract

Different segments of the aorta and its branches show differing susceptibilities to atherosclerosis. To identify metabolic features that may account for plaque formation and sparing, we studied aortic wall respiration and glycolysis proximal and distal to an aortic coarctation in 30 rabbits fed a standard or atherogenic diet. Three months after coarctation, blood pressure in the proximal aorta was elevated, and plaque occupied 98% +/- 28% of the intimal surface compared with 57% +/- 26% for control animals (p less than 0.05). Aortic pressure distal to the stenosis remained normal, but plaque formation was markedly decreased (5% +/- 4%) compared with controls (30% +/- 27%, p less than 0.05). Metabolic studies included measurement of oxygen consumption of proximal and distal aortic walls, lactic acid production, and 2-deoxyglucose uptake. Elevated pressure or hyperlipidemia increased respiration (22.6 +/- 4.0 or 16.3 +/- 6.0 pmol oxygen consumed/min/microgram deoxyribonucleic acid [DNA] vs 5.8 +/- 5.2 for controls; p values less than 0.05) without increasing glycolytic metabolism. The coexistence of hypertension and hyperlipidemia resulted in maximal plaque formation and a sevenfold increase in both oxidative metabolism (46.6 +/- 27.2 pmol oxygen consumed/min/microgram DNA vs 5.8 +/- 5.2 for controls, p less than 0.004) and glycolytic metabolism (44 +/- 10 ng lactic acid produced/90 min/microgram DNA vs 6 +/- 3 for controls, p less than 0.004). In the spared aortic segment distal to coarctation, glycolytic metabolism was increased (10 +/- 8 ng lactic acid produced/90 min/microgram DNA vs 2 +/- 1 for controls, p less than 0.05) but oxidative metabolism remained normal.(ABSTRACT TRUNCATED AT 250 WORDS)

View details for Web of Science ID A1988N409200016

View details for PubMedID 3367436

Abstract

We studied the relationships among intimal plaque area, lumen area, and artery size in 481 sections of the left anterior descending (LAD) coronary artery taken at four standard sampling sites in 125 pressure-perfusion-fixed postmortem adult human hearts. The internal elastic lamina area was considered to be a measure of artery size or potential lumen area. Artery size correlated strongly with intimal plaque area at each LAD level (p less than 0.0001). Stepwise regression analysis revealed that plaque area was the principal determinant of artery size at each LAD level (r2 = 0.20 to 0.33). Sections of arteries with the most intimal plaque (highest quartile) were compared with those with the least plaque (lowest quartile) at each sample site. In the proximal LAD artery, the most severely diseased arteries increased in size 62% but lumen area decreased 25%. In the midportion of the LAD artery, plaque area was 10 times greater in the most diseased arteries, but lumen area remained normal because of an 80% increase in artery size. In the most severely diseased distal LAD artery sections, despite a fourteenfold increase in plaque area, lumen area almost doubled because of a marked increase in artery size. If no enlargement had occurred, the most severely diseased arteries in the proximal LAD segment would have developed a 92% lumen stenosis rather than the observed 25% lumen stenosis. In the distal LAD artery, without enlargement there would have been a 65% lumen stenosis rather than the 85% increase in lumen area that was found.(ABSTRACT TRUNCATED AT 250 WORDS)

View details for Web of Science ID A1988M512000002

View details for PubMedID 3346952

Abstract

A flexible, rotating tip catheter (Kensey catheter) was used to recanalize 24 segments of diseased superficial femoral arteries (from cadavers) that were sewn as xenografts into the femoral, carotid, or aorticorenal arteries of 14 dogs. One perforation occurred; there were emboli in some brains and kidneys, the consequences of which remain unknown. No signs of gross neurologic deficits or limb ischemia were seen at 0-11 days.

View details for Web of Science ID A1987K552900021

View details for PubMedID 3659363

Abstract

Saphenous vein resistance influences graft flow rates and may affect graft patency in lower limb revascularization. To quantitate specifically the contribution of saphenous vein valves to this resistance, 10 human saphenous veins (mean length 68 cm, diameter 0.42 mm, and 5.2 valves per vein) were perfused with water under carefully controlled pressure gradients designed to simulate different peripheral resistances in the outflow bed. The Reynolds number was maintained at 350 to 600, within the physiologic range for in vivo grafts. Veins were perfused under both venous (10 mm Hg) and arterial (100 mm Hg) mean pressures to determine the effects of distension on the overall resistance of the conduit. The valves were bisected according to Leather's techniques and flow was measured in both directions, antegrade (simulating "reversed" grafts) and retrograde (simulating "in situ" grafts). Data (mean +/- standard error) were normalized to the baseline flow for each vein with intact valves and expressed as a percentage change. Data were analyzed by means of Student's t test (p less than 0.05). Baseline antegrade flow with intact valves averaged 71.0 +/- 3.0 ml/min at pressure gradients (delta P) of 10 mm Hg and 95.0 +/- 2.6 ml/min for delta P = 20 mm Hg. After valve incision, antegrade flow (reversed) increased an average of 29% at both pressure gradients. Retrograde flow (in situ) through the bisected valves was only 19% greater than baseline antegrade flow and was significantly less than antegrade flow through bisected valves. The difference is explained by theoretic considerations of stenosis area and orifice shape. The increases in flow did not correlate with vein length or diameter, nor did flow change with different distension pressures.(ABSTRACT TRUNCATED AT 250 WORDS)

View details for Web of Science ID A1987K005600013

View details for PubMedID 3625883

Abstract

Whether human coronary arteries undergo compensatory enlargement in the presence of coronary disease has not been clarified. We studied histologic sections of the left main coronary artery in 136 hearts obtained at autopsy to determine whether atherosclerotic human coronary arteries enlarge in relation to plaque (lesion) area and to assess whether such enlargement preserves the cross-sectional area of the lumen. The area circumscribed by the internal elastic lamina (internal elastic lamina area) was taken as a measure of the area of the arterial lumen if no plaque had been present. The internal elastic lamina area correlated directly with the area of the lesion (r = 0.44, P less than 0.001), suggesting that coronary arteries enlarge as lesion area increases. Regression analysis yielded the following equation: Internal elastic lamina area = 9.26 + 0.88 (lesion area) + 0.026 (age) + 0.005 (heart weight). The correlation coefficient for the lesion area was significant (P less than 0.001), whereas the correlation coefficients for age and heart weight were not. The lumen area did not decrease in relation to the percentage of stenosis (lesion area/internal elastic lamina area X 100) for values between zero and 40 percent but did diminish markedly and in close relation to the percentage of stenosis for values above 40 percent (r = -0.73, P less than 0.001). We conclude that human coronary arteries enlarge in relation to plaque area and that functionally important lumen stenosis may be delayed until the lesion occupies 40 percent of the internal elastic lamina area. The preservation of a nearly normal lumen cross-sectional area despite the presence of a large plaque should be taken into account in evaluating atherosclerotic disease with use of coronary angiography.

View details for Web of Science ID A1987H413900004

View details for PubMedID 3574413

Abstract

We performed transluminal balloon angioplasty in 24 cadaver and nine amputated limb superficial femoral arteries under controlled experimental conditions. The cadaver arteries were excised, restored to in situ length, redistended, and maintained at 100 mm Hg intraluminal pressure at 37 degrees C throughout the angiographic and dilation procedure and during fixation. The amputated limb arteries were dilated and pressure perfusion-fixed after dilation. Quantitative analysis of cadaver vessels revealed that arteries with prominent atherosclerotic lesions had the same internal elastic lamina (IEL) circumference (15.6 +/- 1.0 mm) as those with little or no stenosis (16.8 +/- 0.5 mm) but lumen area (8.8 +/- 1.7 mm2) was markedly reduced compared to nonstenotic sites (20.0 +/- 1.9 mm2, p less than 0.01). Lesions occupied 49 +/- 6% of the area circumscribed by the IEL in cadaver arteries with prominent plaques. After dilatation, lumen areas at stenotic sites were enlarged 43% on histologic sections (12.6 +/- 1.8 mm2 vs 8.8 +/- 1.7 mm2, p less than 0.01) and 31% as determined by angiography (p less than 0.05) when compared to immediately adjacent nondilated regions. The increased lumen area was associated with splitting of the intima near the edges of the plaque, separation of the edges of the plaque from the media, and stretching of the media and adventitia, often with accompanying rupture of the media. There was no evidence of plaque compression, fragmentation, deformation, modeling, or herniation into the media. The detached wedge-shaped edges of the lesions formed flaps projecting into the lumen, resulting in a marked increase in lumen irregularity on cross-section.(ABSTRACT TRUNCATED AT 250 WORDS)

View details for Web of Science ID A1987H681900013

View details for PubMedID 2954524

Abstract

Transesophageal echocardiography (TEE) was used to detect segmental ventricular wall motion abnormalities (SWMAs) associated with ischemia in 49 high-risk patients who had 50 major vascular procedures, including 23 infrarenal aortic, five suprarenal aortic, 14 carotid, seven distal, and one axillofemoral reconstructions. A modified gastroscope tipped with an echocardiographic transducer was inserted into the esophagus and positioned behind the heart to obtain a reproducible cross-sectional view of the left ventricle at the level of the papillary muscles. Twelve patients (24%) had SWMA at baseline, probably representing areas of old infarction. Fourteen patients (28%) had new intraoperative SWMAs. Ten of 14 patients were successfully treated and wall motion was normalized. One of the four patients with persistent SWMA suffered a nonfatal subendocardial infarct; another patient suffered intraoperative cardiac arrest and died. No infarcts were documented in the 10 patients successfully treated. The mortality rate in the entire high-risk group was 6%. Alterations in ventricular wall motion were noted in almost 50% of high-risk patients undergoing major vascular surgery. Seventy-one percent of acute SWMAs were reversed without any evidence of myocardial infarction. TEE allowed early recognition of evolving myocardial ischemia and facilitated immediate and specific fluid and pharamcologic interventions. Continued application of this technique may reduce the incidence and morbidity of perioperative cardiac complications.

View details for Web of Science ID A1987G824600012

View details for PubMedID 3560353

Abstract

We studied the adaptive response of the arterial wall and intimal thickening under conditions of increased flow in an atherogenic model. Blood flow was increased by construction of an arteriovenous fistula between the right iliac artery and vein in six cynomolgus monkeys fed a diet containing 2% cholesterol and 25% peanut oil. The left iliac artery served as the control. Serum cholesterol increased from 135 +/- 22 mg/dl to 880 +/- 129 mg/dl during the experiment. After 6 months, blood flow in the right iliac artery (420 +/- 95 ml/min) was 10 times greater than in the left iliac artery (44 +/- 9 ml/min, p less than 0.005). Flow velocity in the right iliac artery (31 +/- 6 cm/sec) was more than twofold greater than in the left (12 +/- 1 cm/sec, p less than 0.05). Despite the marked difference in blood flow and flow velocity, calculated wall shear stress was the same in both the right (16 +/- 4 dynes/cm2) and left iliac vessels (15 +/- 2 dynes/cm2) because of a twofold increase in lumen diameter (p less than 0.001) of the right iliac artery. Shear stress in the aorta was also normal (12 +/- 2 dynes/cm2). There was no difference in plaque deposition or mean intimal thickness between the right and left iliac arteries. In the right iliac artery there was a twofold increase in media cross-sectional area (p less than 0.001) but no change in media thickness or total wall thickness. Tangential wall tension and tangential wall stress were two times greater on the right than on the left (p less than 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)

View details for Web of Science ID A1987G536100003

View details for PubMedID 3509594

Abstract

We have studied mechanical factors that could determine how stenosis protects against distal atherosclerosis in cynomolgus monkeys fed an atherogenic diet. Critical aortic stenosis was produced by coarctation of the thoracic aorta. After 3 months, coarcted monkeys had a mean aortic pressure gradient of 25 +/- 1 mm Hg and a 76% +/- 2% lumen stenosis. Aortic wall motion was measured by means of in vivo ultrasonic sonomicrometry. Dynamic tracings of aortic pressure and diameter were recorded simultaneously at standard locations proximal and distal to the stenosis and at comparable sites in noncoarcted control animals. In the proximal aorta, mean blood pressure and pulse pressure were increased (p less than 0.05), but wall motion and intimal lesion area were not different from those determined in control monkeys. In the aorta distal to the coarct, mean blood pressure was no different from that in control animals but pulse pressure was diminished; in addition, there was marked reduction of arterial wall motion (p less than 0.001). This was accompanied by a significant reduction of intimal plaque area (p less than 0.05) and acid lipase activity (p less than 0.001). Thus, inhibition of plaque formation in the distal aorta coincided with reduction of pulse pressure and aortic wall motion rather than with blood pressure or hypercholesterolemia. Inhibition of arterial wall motion may account for the sparing effect often encountered in human arteries distal to stenosing atherosclerotic plaques.

View details for Web of Science ID A1987F846600007

View details for PubMedID 3795393

Abstract

In order to identify patients who, having had an initial pulmonary embolism, are likely to develop recurrent emboli despite adequate anticoagulation therapy, ten patients (group 1) with documented recurrent pulmonary embolism during anticoagulation therapy were compared with 31 patients (group 2) who showed no evidence of recurrent emboli during the treatment period. Risk factors for thromboembolic disease were similar between the two groups. Noninvasive venous studies of the lower extremities, including Doppler venous ultrasound and phleborheography (PRG), were performed upon all patients after the initial embolic event. Of the ten patients in group 1, seven (70 per cent) had clinical signs of deep vein thrombosis (DVT). Doppler studies were positive for eight of the nine patients studied, and PRG studies were positive for eight of eight patients tested. In contrast, of the 31 patients who responded well to medical therapy, one patient (3 per cent) had clinical signs of DVT, three patients (10 per cent) had positive Doppler studies and one patient (3 per cent) had a positive PRG. Combined Doppler and PRG studies were positive in 100 per cent of the patients in group 1 but in only 6 per cent of the patients in group 2 (p less than 0.001). The results of this study suggest that patients having an initial pulmonary embolism and DVT of sufficient extent detected by noninvasive studies may be at an increased risk for recurrent PE despite anticoagulation therapy. Insertion of a vena cava filter should be considered in these patients prior to the second embolic event.

View details for Web of Science ID A1986E628000001

View details for PubMedID 3535133

Abstract

Profundaplasty has been advocated as an outflow procedure for threatened failure of aortobifemoral grafts as well as a primary procedure for severe claudication and limb ischemia. The authors reviewed their experience with 27 patients who underwent profundaplasty between 1978 and 1983; five patients (group 1) were treated for threatened or complete aortofemoral graft thrombosis while 22 patients (group 2) underwent profundaplasty as an isolated procedure to treat limb ischemia. Preoperative angiograms were assessed for the presence of five criteria associated with a favourable result from profundaplasty: stenosis of the orifice of the deep femoral artery greater than 50%; minimal disease of the distal artery; disease-free collaterals; reconstitution of a patent superficial femoral or popliteal artery; good popliteal outflow with at least one vessel patent to the foot. Profundaplasty was successful in 100% of group 1 patients but relieved symptoms or healed lesions in only 14% of those in group 2. In the latter group 64% required major amputation. The number of favourable angiographic criteria was similar in both groups. Isolated profundaplasty for limb salvage is not recommended. Angiographic criteria do not reliably identify the few patients who will benefit from profundaplasty alone. The principal role of the procedure is increasing outflow for an aortic graft.

View details for Web of Science ID A1986E143100014

View details for PubMedID 3756653

Abstract

We reviewed 86 consecutive patients undergoing elective carotid endarterectomy to determine whether preoperative clinical and angiographic data could be used to predict the risk of intraoperative cerebral ischemia during carotid occlusion. Electroencephalographic (EEG) monitoring with on-line Berg-Fourier transformation was carried out in all patients. A total of 32 patients (37.2%) underwent intraoperative shunting. Of these, 13 had no EEG changes but underwent shunting because of the surgeon's preference, while 19 patients underwent shunting because of EEG changes consistent with cerebral ischemia. There was one permanent (1.2%) and one transient (1.2%) neurologic deficit. Angiographic findings, clinical histories, and intraoperative EEGs were retrospectively reviewed to determine which risk factors best predicted the occurrence of intraoperative cerebral ischemia. Stroke within six weeks increased the risk of intraoperative cerebral ischemia 20-fold. Intracranial disease and contralateral carotid stenosis increased the risk of ischemia 17-fold and 16-fold, respectively. Statistical summation of all risk factors yielded a probability equation for EEG change that accurately quantitated pre-operative risk. Prospective application of this probability equation may simplify operative decision making if EEG monitoring is not available.

View details for Web of Science ID A1986C085400014

View details for PubMedID 3707335

Abstract

The case is presented of a 38-year-old woman who suffered multiple cerebellar infarctions as a result of emboli from a vertebral artery dissection. Surgical therapy led to a satisfactory recovery. This case emphasizes the importance of an aggressive approach to such lesions.

View details for Web of Science ID A1986A728300020

View details for PubMedID 3950750

Abstract

Increased collagenase activity has been implicated as a basic abnormality in aortic aneurysm formation. We studied a localized aneurysmal change, poststenotic dilatation, and its relation to collagenase and elastase activity of the aortic wall. Cynomolgus monkeys underwent midthoracic aortic coarctation to produce poststenotic dilatation. Serial angiography showed that poststenotic dilatation was minimal or absent at 10 days, just discernible at 3 months, and prominent at 6 months. At the 3-month time interval, collagenase activity in the region of the poststenotic dilatation increased twofold compared with the same region in aortas from animals without poststenotic dilatation (p less than 0.05). There was no change in aortic elastase activity. These data indicate that collagenolysis and aneurysmal dilatation may be induced by local modifications of pressure and/or flow. Increased collagenase activity associated with abdominal aortic aneurysms may not represent an intrinsic metabolic defect but rather a response to altered hemodynamic conditions.

View details for Web of Science ID A1986A069300006

View details for PubMedID 3003406

Abstract

Though the syndrome of carotid artery dissection is well known, "spontaneous" vertebral artery dissection is rarely recognized. We now report clinical and radiologic findings in five patients with presumed vertebral dissection, one pathologically confirmed. Mean age was 35.2 years (range 27-41). Two were men; three women. None had hypertension, vascular disease, or trauma. Headache and neck or occipital pain was prominent in all, often preceding other symptoms. Four of five patients had unilateral partial alteral medullary syndromes, in one accompanied by medial medullary signs. One patient had a cerebellar infarct. Angiography in four patients showed severe irregular stenosis of the distal extracranial vertebral artery (three bilaterally). A fifth patient with irregular stenosis above the vertebral origin had verified extensive dissection in the resected segment. No patient developed late ischemia. Repeat angiography in three showed healing. We conclude that spontaneous vertebral artery dissection, though rare, has recognizable clinical and radiologic features.

View details for Web of Science ID A1985AXN8100022

View details for PubMedID 4089921

View details for Web of Science ID A1985AAR0800028

View details for PubMedID 3965756

Abstract

Fluid velocities were measured by laser Doppler velocimetry under conditions of pulsatile flow in a scale model of the human carotid bifurcation. Flow velocity and wall shear stress at five axial and four circumferential positions were compared with intimal plaque thickness at corresponding locations in carotid bifurcations obtained from cadavers. Velocities and wall shear stresses during diastole were similar to those found previously under steady flow conditions, but these quantities oscillated in both magnitude and direction during the systolic phase. At the inner wall of the internal carotid sinus, in the region of the flow divider, wall shear stress was highest (systole = 41 dynes/cm2, diastole = 10 dynes/cm2, mean = 17 dynes/cm2) and remained unidirectional during systole. Intimal thickening in this location was minimal. At the outer wall of the carotid sinus where intimal plaques were thickest, mean shear stress was low (-0.5 dynes/cm2) but the instantaneous shear stress oscillated between -7 and +4 dynes/cm2. Along the side walls of the sinus, intimal plaque thickness was greater than in the region of the flow divider and circumferential oscillations of shear stress were prominent. With all 20 axial and circumferential measurement locations considered, strong correlations were found between intimal thickness and the reciprocal of maximum shear stress (r = 0.90, p less than 0.0005) or the reciprocal of mean shear stress (r = 0.82, p less than 0.001). An index which takes into account oscillations of wall shear also correlated strongly with intimal thickness (r = 0.82, p less than 0.001). When only the inner wall and outer wall positions were taken into account, correlations of lesion thickness with the inverse of maximum wall shear and mean wall shear were 0.94 (p less than 0.001) and 0.95 (p less than 0.001), respectively, and with the oscillatory shear index, 0.93 (p less than 0.001). These studies confirm earlier findings under steady flow conditions that plaques tend to form in areas of low, rather than high, shear stress, but indicate in addition that marked oscillations in the direction of wall shear may enhance atherogenesis.

View details for Web of Science ID A1985AGS1000010

View details for PubMedID 3994585

Abstract

Purified acid lipase was previously shown to hydrolyze the artificial substrate, alpha-naphthyl palmitate, as well as triglycerides and cholesteryl esters and to form cholesteryl esters. To determine to what extent these activities are associated with acid lipase-containing cells in atherosclerotic plaques, we examined rabbit aortas at different stages of experimental lesion induction and human atherosclerotic arteries. Assays of cholesteryl ester formation, and alpha-naphthyl palmitate and cholesteryl ester hydrolysis were performed on homogenates of lesions and the hydrolysis of the artificial fatty acid ester was used as a histochemical marker to identify acid lipase positive foam cells in sections of the same lesions. The volume of lesions occupied by cells stained for acid lipase correlated strongly with the enzyme activities of the arterial homogenates. These results suggest that acid lipase-containing cells may mediate the accumulation of cholesteryl ester during atherogenesis. Since acid lipase activity marks macrophages, these methods may be useful for relating macrophage distribution and function to lesion progression, regression, and complication.

View details for Web of Science ID A1985AHN6600009

View details for PubMedID 4004991

Abstract

Doppler ultrasound and PRG were compared with the results of venography in 216 limbs with suspected DVT. Equivocal or conflicting noninvasive test results were obtained in 40 limbs and thrombi were demonstrated venographically in 18 of these (45 per cent). In the remaining 176 limbs, the sensitivity of the noninvasive test was 88 per cent and the specificity was 99 per cent. Treatment may be confidently chosen without venographic confirmation when the results of Doppler ultrasound and PRG agree. Venography is indicated in the minority of instances when the two noninvasive test results do not agree or are equivocal.

View details for Web of Science ID A1984TH03700009

View details for PubMedID 6474326

Abstract

The role of heart rate in the development of coronary atherosclerosis was assessed in adult male cynomolgus monkeys (Macaca fascicularis). Heart rate was lowered in six animals by surgical ablation of the sinoatrial node. A sham procedure, which included all of the surgical steps except for sinoatrial node ablation, was carried out in eight animals. All of the monkeys were fed an atherogenic high cholesterol diet for 6 months, and heart rates were monitored repeatedly by telemetry during 24-hour test periods. Coronary atherosclerosis in animals with postoperative heart rates less than the preoperative mean for all of the animals that underwent surgery was less than half that of animals with heart rates above the mean or of diet-fed control animals not subjected to surgery. Groups did not differ in blood pressure, serum lipids, or body weight. These results suggest that heart rate in itself may contribute to the mechanisms by which behavioral patterns and physical training influence coronary artery disease.

View details for Web of Science ID A1984TL54000034

View details for PubMedID 6484569

Abstract

The human abdominal aorta is particularly susceptible to the formation of aneurysms with atrophic walls. This aortic segment normally has fewer medial lamellar units than would be expected for a mammalian aorta of comparable diameter as well as far fewer medial vasa vasorum than would be expected for an aortic wall of comparable thickness. To test the hypothesis that ischemia and/or loss of normal lamellar architecture are predisposing factors for aneurysm formation, we used the pig thoracic aorta, which is furnished with 75 medial layers and vasa supplying the outer two thirds. Vasal blood flow was surgically ablated, and crushing injury was used to reduce the number of intact lamellar units. Mural ischemia alone resulted in necrosis of cells in the medial zone furnished by vasa but did not lead to aneurysmal dilatation, and all the fibrous tissue layers persisted during the 2-month observation period. Mechanical injury resulted in aneurysms in both ischemic and nonischemic aortic segments, but only if fewer than 40 intact lamellae remained and the average tension per lamellar unit exceeded three times the normal value of 1316 +/- 202 dynes/cm (4543 +/- 1624 for ischemic and 4087 +/- 871 for nonischemic segments; p less than 0.01 for each). We conclude that a critical reduction in the number of intact lamellar units results in aneurysmal dilatation. Protracted medial ischemia due to intimal plaque formation in the avascular abdominal aorta may eventually reduce the number of intact lamellae and favor the development of aneurysms.

View details for Web of Science ID A1984ST49000011

View details for PubMedID 6481894

Abstract

We performed percutaneous transluminal angioplasty (PTA) in 97 limbs of 86 patients with end-stage occlusive disease in whom vascular reconstruction was not possible. Most patients required dilation of long-segment occlusions and/or multiple lesions. Angiographic appearance was improved in 87 limbs of 78 patients (90%). Ankle-brachial pressure index increased from 0.40 +/- 0.03 to 0.64 +/- 0.03, and increased more than 0.15 in 63% of the limbs. Major amputation was required in 19 of the 87 limbs (22%) following PTA. The incidence of restenosis was 19% at three months, 42% at six months, and 57% at one year. Repeated PTA successfully maintained vascular patency in ten limbs, and four patients have since had successful distal bypass. Two limbs that initially improved needed amputation four to 19 months after dilatation. Follow-up ranged from one to 45 months; overall limb salvage rate was 76%. Thus PTA can enhance limb salvage in poor-risk patients with end-stage disease.

View details for Web of Science ID A1983RK19800018

View details for PubMedID 6225410

Abstract

Cyclic stretching of smooth muscle cells in culture resulted in a two- to fivefold increase in protein and collagen synthesis. The same in vitro system was utilized to relate changes in smooth muscle cell morphology to mechanical stress. Smooth muscle cells, grown in culture from rabbit aorta explants, were transferred to purified elastic membranes derived from bovine aorta. The membranes were either subjected to stretching and relaxation 52 times per minute or stretched and held stationary for 8, 48, or 56 hr. Profiles of rough endoplasmic reticulum (RER) were counted and myofilament content estimated from electron micrographs of 100 cells for each experiment. Cells from cyclically stretched preparations were compared with stationary cells derived from the same subculture. Myofilaments were largely replaced by RER in cyclically stretched cells and there was a reciprocal relationship between RER and myofilament content in individual cells. In cells from stationary preparations, myofilament content also diminished with time but RER profiles were few. At 56 hr, RER profiles numbered 16.7 +/- 1.7 in stretched cells compared with 3.6 +/- 1.3 in stationary cells (P less than 0.05). Cyclically stretched cells formed numerous intercellular contacts and showed little evidence of cytoplasmic degradation while stationary cells showed few contacts and contained numerous cytosomes and lamellar bodies. The results suggest that cyclic stretching resulted in the formation of RER or the preservation of myofilaments and that immobility resulted in the disappearance of myofilaments and cytoplasmic degradation.(ABSTRACT TRUNCATED AT 250 WORDS)

View details for Web of Science ID A1983RY15800004

View details for PubMedID 6686270

Abstract

The distribution of nonstenosing, asymptomatic intimal plaques in 12 adult human carotid bifurcations obtained at autopsy was compared with the distribution of flow streamline patterns, flow velocity profiles, and shear stresses in corresponding scale models. The postmortem specimens were fixed while distended to restore normal in vivo length, diameter, and configuration. Angiograms were used to measure branch angles and diameters, and transverse histological sections were studied at five standard sampling levels. Intimal thickness was determined at 15 degrees intervals around the circumference of the vessel sections from contour tracings of images projected onto a digitizing plate. In the models, laser-Doppler anemometry was used to determine flow velocity profiles and shear stresses at levels corresponding to the standard specimen sampling sites under conditions of steady flow at Reynolds numbers of 400, 800, and 1200, and flow patterns were visualized by hydrogen bubble and dye-washout techniques. Intimal thickening was greatest and consistently eccentric in the carotid sinus. With the center of the flow divider as the 0 degree index point, mid-sinus sections showed minimum intimal thickness (0.05 +/- 0.02 mm) within 15 degrees of the index point, while maximum thickness (0.9 +/- 0.1 mm) occurred at 161 +/- 16 degrees, i.e., on the outer wall opposite the flow divider. Where the intima was thinnest, along the inner wall, flow streamlines in the model remain axially aligned and unidirectional, with velocity maxima shifted toward the flow divider apex. Wall shear stress along the inner wall ranged from 31 to 600 dynes/cm2 depending on the Reynolds number. Where the intima was thickest, along the outer wall opposite the flow divider apex, the pattern of flow was complex and included a region of separation and reversal of axial flow as well as the development of counter-rotating helical trajectories. Wall shear stress along the outer wall ranged from 0 to -6 dynes/cm2. Intimal thickening at the common carotid and distal internal carotid levels of section was minimal and was distributed uniformly about the circumference. We conclude that in the human carotid bifurcation, regions of moderate to high shear stress, where flow remains unidirectional and axially aligned, are relatively spared of intimal thickening. Intimal thickening and atherosclerosis develop largely in regions of relatively low wall shear stress, flow separation, and departure from axially aligned, unidirectional flow. Similar quantitative evaluations of other atherosclerosis-prone locations and corresponding flow profile studies in geometrically accurate models may reveal which of these hemodynamic conditions are most consistently associated with the development of intimal disease.

View details for Web of Science ID A1983RP43700008

View details for PubMedID 6627609

View details for Web of Science ID A1983QM39000006

View details for PubMedID 6403773

Abstract

We have treated 13 patients with limb-threatening ischemia caused by acute arterial thrombosis with selective arterial infusion of streptokinase. The indications for thrombolytic therapy included medical contraindication to surgery, surgically inaccessible thrombi, arterial thrombosis following percutaneous transluminal angioplasty, and thrombosed distal arterial bypass. Patients were evaluated with arteriography, Doppler segmental arterial pressure studies, and coagulation profile. Objective evidence of complete or partial thrombolysis was demonstrated in 11 of the 13 patients (85%). Treatment after thrombolytic therapy included percutaneous transluminal angioplasty in six patients and distal bypass in two patients. Of five patients who had received no additional treatment, three required amputation. Overall limb salvage was achieved in 10 of the 13 patients. The most serious complications were puncture site bleeding in five patients, acute renal failure in one patient, and retroperitoneal hemorrhage in another patient. Bleeding was more frequent in patients with decreased serum fibrinogen levels. Although lysis of acute arterial thrombi can be achieved, thrombolytic therapy alone will allow limb salvage in only a few patients. Selective thrombolytic therapy with streptokinase must be used with caution and is associated with serious complications.

View details for Web of Science ID A1983QT48400013

View details for PubMedID 6222500

Abstract

We studied immediate and long-term alterations in human atherosclerotic arteries subjected to balloon dilatation. Pathologic material included vessels obtained at amputation or autopsy that had been previously dilated in vivo and cadaver vessels dilated under physiologic pressure and temperature. All vessels were pressure-perfusion fixed, and morphologic observations were correlated with sequential angiograms obtained in 36 patients. Balloon dilatation resulted in disruption of both the plaque and the artery wall, with separation of the plaque from the tunica media, rupture of the tunica media, and stretching of the tunica adventitia to increase lumen cross-sectional area. The intimal plaque protruded into the lumen, accounting for the angiographic appearance of local flaps and dissection channels. Remodeling occurred by readherence of the intimal flaps with little change in plaque volume. Achievement of a sufficient radius of curvature may be necessary to achieve long-term patency. Restenosis may occur because of insufficient dilatation but may also result from extention of dissection channels into nondilated segments of the artery.

View details for Web of Science ID A1982PS79300020

View details for PubMedID 6216619

Abstract

In cases of occlusion of the superficial femoral artery exceeding a length of 10 cm, accompanied by involvement of the popliteal artery and poor runoff, percutaneous transluminal angioplasty is unfavorable. However, when such advanced occlusive disease is present in patients for whom vascular surgery is not feasible, this technique can be of value by averting or at least postponing amputation. Percutaneous transluminal angioplasty was used to recanalize long segments (10-36 cm) of occluded or stenotic femoropopliteal arteries in 21 patients. Results were evaluated by means of pre- and postangioplasty arteriograms and measurements of pressure indices. The initial success rate was 76%; the success rate on 5-24 month follow-up was 67%. The long-term benefit can be improved by other measures, such as stopping cigarette smoking, exercise, long-term anticoagulation therapy, and early detection and treatment of restenosis.

View details for Web of Science ID A1982MW47300022

View details for PubMedID 6459724

Abstract

Erectile impotence is not a simple problem and it is important to recognize that the presence of a possible organic cause does not rule out emotional difficulties or sexual maladjustment. Behavioral therapy and surgery have an important role in treating this symptom. By careful pre-treatment evaluation the most appropriate therapy can be selected. It has been our general rule that when neither clear organic nor psychogenic problems lie at the root of the difficulty, a trial of behavioral therapy is the most appropriate procedure. If no success is achieved after an adequate trial of therapy re-evaluation and recommendation for a prosthetic implant can be made.

View details for Web of Science ID A1982NQ71600011

View details for PubMedID 7062415

Abstract

The referral pattern of impotent men from a urology clinic to a sexual dysfunction clinic was investigated. Only 62% of referred patients made such recommended appointments. Of the patients for whom sex therapy was recommended, only 32% accepted this recommendation. Of those accepting a recommendation for treatment, 57% prematurely terminated treatment against medical advice. The implications of this for referring physicians and alternative treatment approaches are discussed.

View details for Web of Science ID A1982PU00500006

View details for PubMedID 7159220

Abstract

We performed a prospective randomized clinical study to determine whether use of a thigh tourniquet influences the incidence of deep venous thrombosis. The lower limbs of patients who were scheduled for elective surgery on the fore part of the foot were randomized and assigned to one of three treatment categories: Group I, no tourniquet; Group II, exsanguination by an Esmarch bandage before tourniquet application; and Group III, exsanguination by elevation of the extremity prior to application of a tourniquet. The 117 limbs of seventy-one patients included in this study were evaluated preoperatively and twenty-four and seventy-two hours postoperatively with 125I-labeled fibrinogen, and preoperatively and seventy-two hours postoperatively with Doppler ultrasound studies and phleborheography. The findings in all of the Doppler ultrasound studies and all of the phleborheograms were normal. Two of the 125I-fibrinogen studies were positive, but subsequent contrast venography revealed that these were false-positive findings. We therefore concluded that the use of a thigh tourniquet does not increase the risk of deep venous thrombosis in patients who have had an operation on the fore part of the foot.

View details for Web of Science ID A1982NF27400007

View details for PubMedID 7056771

Abstract

We studied 218 patients (372 limbs) and 25 normal subjects (50 limbs) with resting ankle index (RAI), treadmill exercise (TE), and postocclusive reactive hyperemia (PORH) to determine whether diagnostic accuracy is improved through the use of stress testing. In addition, we studied 10 patients with stable claudication (20 limbs) to determine the reproducibility of the three measures. RAI was the most reproducible measure, with the smallest variance between testing days (P less than 0.001). RAI differentiated between arteriographically diseased and normal limbs with a sensitivity of 97% and a specificity of 100%, whereas the corresponding values for TE were 97% and 96% and for PORH 89% and 96%. Recovery to baseline index was prolonged in the diseased group compared with normal (p less than 0.001 for both TE and PORH), but this was of limited discriminative value. Receiver-operating characteristic curve analysis documented that RAI was as diagnostically useful as TE and that both were more valuable than PORH (P less than 0.02). However, the routine addition of stress testing increased diagnostic yield by only 1.6% and cost $1100 for each limb correctly diagnosed through the addition of stress testing. RAI is a simple, accurate, and reproducible test. Routine stress testing is not cost effective, adding little diagnostic information to RAI, and it should be reserved for the small subset of symptomatic patients with normal RAI.

View details for Web of Science ID A1982NS61100016

View details for PubMedID 7079971

View details for Web of Science ID A1982PW03000001

View details for PubMedID 7144160

Abstract

A case of abdominal aortic aneurysm with Bechçet's disease and a review of two similar cases previously reported are presented. This case and additional review of other reported major vascular complications of Behçet's disease lead us to conclude that the pathogenesis of the abdominal aneurysm is related to involvement of the aortic wall or vasa vasorum by the Behçet's disease process. Surgical treatment of this rare complication by Behçet's disease should include extra-anatomic bypass if the possibility of infection cannot be definitely excluded.

View details for Web of Science ID A1982NE89500023

View details for PubMedID 6460336

Abstract

Thirty patients with end-stage atherosclerosis, being considered for amputation, were treated by percutaneous transluminal angioplasty (PTA). All had very poor run-off, and none was a candidate for arterial reconstruction. Occluded segments of the iliac, femoral, popliteal, and tibial arteries measuring up to 21 cm were recanalized, resulting in an increased ankle/brachial systolic pressure index despite significant distal occlusive disease. Ischemic symptoms were relieved in 22 patients, and the overall limb salvage rate (2- to 17-month follow-up) was 73%.

View details for Web of Science ID A1982MZ66300009

View details for PubMedID 6459607

Abstract

Forty-two patients suspected of having unilateral upper extremity deep venous thrombosis (DVT) were evaluated with Doppler ultrasonography and phleborheography (PRG). Venography was performed on 23 upper extremities (54%). Doppler ultrasonography and PRG produced similar accuracy (82%) in detecting upper extremity DVT when compared with venography. The accuracy improved to 91% when the results of both tests were considered together. It is concluded that Doppler ultrasonography and PRG, when used together, are useful, rapid, and accurate techniques for diagnosing upper extremity DVT.

View details for Web of Science ID A1982NQ43500017

View details for PubMedID 7071746

Abstract

We studied 133 patients with arteriographic evidence of lower limb arterial disease and 34 normal volunteers to determine the most useful means of expressing ankle pressure. Representative ranges were determined for each of six symptomatic categories. Receiver operating characteristic curve analysis showed that ankle index (ankle to brachial pressure ratio) and brachial-ankle pressure gradient were more valuable than absolute pressure in discriminating between normal and disease extremities. In contrast, absolute ankle pressure was the best predictor of nonviability (limb requiring bypass for salvage or amputation). An absolute pressure cutoff of 6mm Hg correctly identified 86% of viable limbs and 77% of nonviable limbs. Thus, the diagnostic accuracy of the three methods of expressing ankle pressure depends on the context in which they are to be used, and it appears that ankle index and gradient are most appropriate for defining the presence of disease, while absolute pressure correlates best with viability.

View details for Web of Science ID A1982PJ84400008

View details for PubMedID 7125893

View details for Web of Science ID A1982NY43100001

View details for PubMedID 7045530

View details for Web of Science ID A1982NM65700014

View details for PubMedID 6461884

Abstract

Thoracic aortic coarctations were produced in cynomolgus monkeys by one of three methods: circumferential banding to produce a symmetric channel with a rigid wall, lateral plication to provide an asymmetric channel with splitting on one side, and lateral plication plus banding to provide a rigid asymmetric channel. The degree of luminal constriction was 58 +/- 12%, with no significant difference among groups. After 3-12 months on an atherogenic diet, the coarctation channels were remarkably free of lesions compared with the aorta immediately proximal to the coarctation (p less than 0.001). Banding resulted in sharp circumferential termination of the lesions just proximal to constriction. Lateral plication resulted in an oblique termination of proximal disease wtih sparing opposite the plication. Lesions distal to coarctations occurred in a pattern related to the configuration of the coarctation channel and tended to form immediately below the plication. Sparing in and immediately beyond the constriction was independent of the rigidity of the aortic wall or of previous disruptive endothelial or medial injury associated with the operative procedure. Endothelium was preserved within the coarctation channel and over all lesions and distal to the constriction. The findings suggest that flow separation and instability tend to favor atherogenesis, whereas increased flow velocity per se may exert a protective effect.

View details for PubMedID 7249326

View details for Web of Science ID A1981LC27600004

View details for PubMedID 7464108

View details for Web of Science ID A1981LR99200003

Abstract

Starling's hypothesis of forces governing fluid movement across capillary membranes suggests that any unopposed decrease in intracapillary colloid oncotic pressure (COP) or increase in capillary permeability should result in increased interstitial fluid. Iso-oncotic increase in pulmonary artery wedge (PAW) causes pulmonary dysfunction. Isobaric reduction of COP with normal capillary permeability does not result in pulmonary interstitial edema. Because sepsis is a frequent antecedent of clinical pulmonary dysfunction, the question was asked: does reduction in the COP-PAW gradient in the presence of sepsis result in increased pulmonary dysfunction? Twenty baboons were studied: group 1--control, group 2--4-h constant infusion of E. coli, group 3--plasmapheresis alone, group 4--plasmapheresis followed by sepsis. Ringer's lactate was infused to keep PAW constant. Arterial and mixed venous blood gases were drawn and the intrapulmonary shunt (QS/QT) was calculated. The data were compared using Tukey's HSD test and one way analysis of variance. Plasmapheresis alone resulted in a 68% reduction in COP (15 +/- 2.9 (SD) torr to 4.6 +/- 0.6 in group 3 and 16.5 +/- 4.3 to 5.7 +/- 0.9 in group 4, p less than 0.05). Sepsis resulted in an increase in QS/QT in all septic animals. There was no increased QS/QT in those animals that had sepsis added to plasmapheresis, group 4 (p less than 0.05). These data indicate that sepsis leads to pulmonary dysfunction but that this dysfunction appears to be independent of colloid oncotic forces.

View details for Web of Science ID A1981LC19700004

View details for PubMedID 7006918

Abstract

The scientific literature on the treatment of penile erectile dysfunction contains numerous contradictory reports on the relative frequency of organic causes of impotence and the treatment results of behavioral sex therapy. One explanation for these contradictory findings is the hypothesis that different investigators are studying different subsamples of the symptomatic population. This study investigated differences in characteristics of men who initially consulted a urologist with a complaint of impotence versus those who self-referred themselves to a sexual dysfunction clinic. Self-referred sexual dysfunction patients were more often white, more often had psychogenic etiologies to their difficulties, were more often of higher socioeconomic class, and had a much better response to psychological interventions. This study suggests that future studies concerning the etiology and treatment of impotence need to specify population characteristics such as referral source and screening criteria. It may be necessary to develop alternative treatment techniques for men who present to nonpsychiatric sources for help with psychogenic impotence.

View details for Web of Science ID A1981MA17100004

View details for PubMedID 7255634

Abstract

Patients with a presenting complaint of erectile dysfunction were extensively investigated by a research team consisting of a urologist, vascular surgeon, psychiatrist and psychiatric social worker. Patients were assigned to organic and psychogenic groups according to specified criteria. Multiple comparisons of psychogenic and organic impotence cases on scores derived from the Derogatis Sexual Functioning Inventory (DSFI) did not differentiate the two groups. This inventory did, however, manifest numerous relationships with demographic variables. Failure to identify a psychological profile characteristic of psychogenic impotence was attributed to the heterogenity of this diagnostic grouping and selection processes in seeking treatment for such disorders.

View details for Web of Science ID A1981MT76200006

View details for PubMedID 7345162

View details for Web of Science ID A1981LJ88400017

View details for PubMedID 7206151

Abstract

Ten patients with symptoms of cerebral ischemia were found to have totally occluded internal carotid arteries with significant external carotid artery stenosis or occlusion. Eight patients underwent external carotid endarterectomy, and two patients underwent saphenous vein bypass to the external carotid artery from the subclavian artery. Cerebral blood flow was measured with 133Xe in six patients preoperatively and in five postoperatively. Four of the six patients had diminished mean flow on the affected side, and three had diminished flow in the contralateral side. All patients had abnormalities in regional cerebral blood flow. Postoperatively, all patients had significant improvement in mean blood flow on the side treated with operation (15% to 39%), and four had improvement of blood flow on the contralateral side (12% to 52%). All had improvement in regional cerebral blood flow. Nine of the 10 patients were relieved of their symptoms. One patient, despite improvement in cerebral blood flow, continued to have diminished cerebral flow and symptoms postoperatively. Subsequent extracranial-intracranial bypass relieved his symptoms and his cerebral blood flow returned to normal. Thus external carotid artery revascularization is effective in increasing total and regional cerebral blood flow and in relieving symptoms of internal carotid artery occlusion and external carotid stenosis. Cerebral blood flow measurement with 133Xe is useful in preoperative patient selection and objective assessment of operative results.

View details for Web of Science ID A1981LT11100015

View details for PubMedID 7245035

View details for Web of Science ID A1981LW89400002

View details for PubMedID 7242060

Abstract

Previous investigators have examined the luninal surfaces of perfusion fixed rabbit aortas and reported endothelial damage about aortic ostial flow dividers. These changes have been considered to represent in vivo endothelial injury predisposing to atherosclerosis at these sites. Although standard pressure perfusion fixation techniques were used by these investigators, the fixed aortas were usually cut, bent open and pinned to flat surfaces before viewing. Such procedures distort the aortic media and could result in artifactual endothelial disruptions. We therefore studied the effect of post-fixation aortic manipulation on luminal surface morphology about aortic ostia. Rabbit aortas were fixed by perfusion in situ, while intra-aortic pressure was continuously monitored. When the aortas were opened by means of two parallel, lateral, longitudinal cuts, so that bending and pinning was avoided and normal vessel curvature was maintained, no endothelial disruption occurred about aortic ostia. When aortas were opened with one cut, bent open and pinned flat, ostial flow dividers were somewhat stretched and elongated and there was endothelial disruption in the form of spindle cell formation at the center portion of the flow dividers. Endothelial deformation due to bending during pinning probably occurs preferentially at the flow dividers because the media is thickest at this point. The greater deformability at the adjacent media and differences in compliance between media and intima results in stretching, bending and plication of the intima over the projecting flow divider. Studies attempting to relate endothelial changes to differences in shearing stress about ostia must take into account deformations introduced by post-fixation manipulation.

View details for PubMedID 6997984

View details for Web of Science ID A1980JJ18300005

View details for PubMedID 6986511

Abstract

Reduction of blood pressure and serum cholesterol levels is associated with reduced risk for the development of arteriosclerotic disease. Experimental studies indicate that reduced cholesterol levels result in arrest or regression of established diet-induced arterial lesions, but the effects of blood pressure reduction on such lesions are not clear. In order to investigate the effects of blood pressure on the regression of established lesions, we induced aortic intimal disease in cynomolgus monkeys by means of an artherogenic diet, produced midthoracic aortic coarctations, and restored the animals to low-cholesterol diets for 6 months. Diet control animals were neither coarctated nor restored to low-cholesterol diets. Animals with severe aortic stenosis and the regression diet had the same degree of abdominal aortic atherosclerosis and mural cholesterol content as diet control animals but esterified cholesterol and collagen content was elevated. Animals with mild coarctation and consuming the regression diet had significantly less abdominal aortic atherosclerosis than the diet control animals or the animals with severe coarctation. Although stenosis prevented the induction of lesions in previous experiments, the present study indicates that it did not reverse or delay progression of previously established lesions. The effect of pressure reduction on atherogenesis, even in the presence of reduced cholesterol levels, may depend on the extent and nature of the underlying lesions.

View details for Web of Science ID A1980JZ48400011

View details for PubMedID 6770479

View details for Web of Science ID A1980KP65700007

View details for PubMedID 7420717

Abstract

Six patients with rest pain and gangrene or ulceration were treated by percutaneous transluminal angioplasty using the Grüntzig balloon catheter. All had superficial femoral artery occlusion with severe stenosis or occlusion of the popliteal and tibial arteries. Two patients had previous distal bypass procedures which had failed, and none was a candidate for arterial reconstruction. The superficial femoral artery was recanalized in five patients with an increase in the above-knee pressure index from 0.5 +/- 0.1 to 1.0 +/- 0.1 (P less than 0.001) and ankle pressure index from 0.2 +/- 0.1 to 0.5 +/- 0.1 (P less than 0.001). All five patients avoided early amputation and were able to ambulate when discharged. The sixth patient could not be recanalized and required above-knee amputation. Restenosis of the recanalized superficial femoral artery occurred in four patients 2 to 5 months later, and repeat transluminal angioplasty was successful in three patients. Two patients have required below-knee amputation 4 and 5 months after recanalization. Transluminal angioplasty can extend our capability of early limb salvage.

View details for Web of Science ID A1980JV08900016

View details for PubMedID 7376081

View details for Web of Science ID A1980JU77400003

View details for PubMedID 6771465

Abstract

Changes in blood flow to the pelvis were monitored by measurement of penile blood pressures before and after 38 aortoiliac vascular reconstructions. An increase in penile pressure was noted in 14 patients (37%), a decrease was seen in eight patients (21%), and no change occurred in 16 patients (46%). These changes could have been predicted by matching arteriograms to the surgical procedure performed. Preoperative impotence was present in 27 patients (17%). In this group a postoperative increase in penile pressure was associated with restoration of erectile capability in eight of 11 patients. Only one of 10 patients with an unchanged penile pressure regained sexual potency. In contrast, none of the eight patients whose penile pressures decreased had recurrence of erectile capability. Six of these patients had end-to-end aortobifemoral grafts, and concurrent external iliac disease prevented retrograde flow to the internal iliac vessels.

View details for Web of Science ID A1979JB42600003

View details for PubMedID 515949

View details for Web of Science ID A1979GP20400004

View details for PubMedID 436430

Abstract

The effects of hemodynamic resuscitation with protein-containing or balanced salt solution were studied prospectively in 29 patients undergoing abdominal aortic surgery. Blood loss was replaced with packed red cells and extracellular volume with either Ringer's Lactate (RL) or 5% albumin in Ringer's lactate (ALB). Fluids were given to maintain the pulmonary capillary wedge pressure (PCWP) equal to or within 5 torr above preoperative (PO) levels, the cardiac output (CO) equal to or greater than preoperative values, and the urine output at least 50 ml/hr. Serum colloid osmotic pressure (COP), CO, PCWP, the gradient between COP and PCWP (COP-PCWP), and intrapulmonary shunt (Qs/Qt) were measured PO, intraoperatively (IO), and daily for 3 days. The measured variables were similar PO in both groups. Operation time, estimated blood loss, and transfusions were similar. Total fluids received for resuscitation (day of operation) was 11.3 +/- 0.8 liters (RL) and 6.2 +/- 0.4 liters (ALB). Fluid balance at the end of resuscitation was 8.4 +/- 0.8 liters (RL) and 3.4 +/- 0.5 liters (ALB). Maximum decrease in COP was 40% (P less than 0.001) in the RL group and was insignificant in the ALB group. The COP-PCWP decreased from 11 +/- 1 to 2 +/- 1 in RL (P less than 0.001) and insignificantly in ALB. Qs/Qt increased slightly in both groups following operation but was not different between groups. Fluid balance, total fluid infused, sodium balance, total sodium infused, COP, or COP-PCWP did not significantly correlate with Qs/Qt. Two patients in the ALB group experienced pulmonary edema associated with normal COPs and elevated PCWPs. There were no cases of pulmonary edema associated with low COPs and normal PCWPs in the crystalloid group. These data seriously question the necessity to maintain COP by using protein-containing solutions during acute hemodynamic resuscitation. When titrated to physiological end points, even large volumes of balanced salt solutions are tolerated well.

View details for Web of Science ID A1979GG98400002

View details for PubMedID 419454

View details for Web of Science ID A1979HY01800010

View details for PubMedID 117259

View details for Web of Science ID A1979JB37300077

View details for PubMedID 120014

Abstract

Plasma colloid osmotic pressure was reduced by 76% (from 19.6 +/- 0.6 to 4.7 +/- 1.5 mm Hg) in five baboons while pulmonary capillary hydrostatic pressure was maintained at a normal level. This resulted in fluid retention, weight gain, peripheral edema and ascites, but no pulmonary edema. Thoracic duct lymph flow increased 6-fold and pulmonary lymph flow 7-fold. Thoracic duct lymph had a lower colloid osmotic pressure (2.0 +/- 0.7 mm Hg) than plasma (4.7 +/- 1.5 mm Hg), whereas the colloid osmotic pressure of pulmonary lymph (4.7 +/- 0.7 mm Hg) was the same as that of plasma. The lymph-plasma ratio for albumin fell in thoracic duct lymph but remained unchanged in pulmonary lymph. The difference between plasma colloid osmotic pressure and pulmonary artery wedge pressure decreased from 15.3 +/- 1.9 to -0.7 +/- 2.9 mm Hg. Despite this increase in filtration force, the lungs were protected from edema formation by a decrease of 11 mm Hg in pulmonary interstitial colloid osmotic pressure and a 7-fold increase in lymph flow.

View details for Web of Science ID A1978GB22500013

View details for PubMedID 101311

View details for Web of Science ID A1977DZ09000008

View details for PubMedID 409885

View details for PubMedID 411133

View details for Web of Science ID A1977CZ00900019

View details for PubMedID 402505

Abstract

Retrospective analysis of forty-two consecutive patients with flail chest injuries admitted to the Trauma Research Unit of the Naval Regional Medical Center, San Deigo from June 1972 to July 1975 compared ventilatory and nonventilatory management. The actual need for ventilatory support in these patients was determined by analyzing their records for evidence of significant pulmonary dysfunction. This allowed division of patients into three groups: "appropriately" ventilated; "inappropriately" ventilated; and nonventilated. Admission PO2 in the "appropriately" ventilated patients was significantly lower than in the other two groups because the former were admitted with respiratory distress and hypoxemia. Significantly more complications occurred in the ventilated groups than in the nonventilated. Treatment-associated complications were more frequent in the ventilated groups. Because of these findings, we belive that mechanical ventilation should be used in the treatment of flail chest injuries only for significant pulmonary dysfunction and not for the purpose of stabilizing the chest wall. If respiratory support is required, it should be discontinued when normal gas exchange has been restored.

View details for Web of Science ID A1976CP95100020

View details for PubMedID 998864

View details for Web of Science ID A1976CL46400114

View details for PubMedID 828313

View details for Web of Science ID A1976CL46400075

View details for PubMedID 1019844

Abstract

Quantitative peritoneal lavage was performed in 52 children with blunt abdominal trauma to determine the presence of intraabdominal injuries. A strongly positive lavage was 100% accurate in diagnosing an intraabdominal injury requiring operation. A negative lavage demonstrated absence of a significant intraperitoneal injury with 100% accuracy. A weakly positive lavage was not diagnostic and required additional evaluation including intravenous pyelography echography, and arteriography. Diagnosis and treatment was prompt, and in 20 of 21 cases, operation was performed within 4 hr. Peritoneal lavage was found to be safe and much more accurate than physical examination in diagnosing significant intraabdominal injury.

View details for Web of Science ID A1976CQ10100011

View details for PubMedID 1003309

Abstract

Thirty-one anesthetized dogs were surface cooled at 5 C and rewarmed after a variable period. Respiration was controlled with a volume respirator. When cardiac arrest occurred, circulation was provided with the mechanical ventricular assistance (MVA) device in 23 dogs. Of the animals maintained for four hours below 10 C on the MVA, 83% were successfully resuscitated. None of the dogs maintained for two hours below 10 C without circulation could be resuscitated. Eleven dogs were studied for a long-term survival after chest closure. Only four of them survived longer than three days. Death after rewarming was due to severe pulmonary insufficiency. Results of this study suggest that provision of oxygenation and a pulsatile circulation during hypothermia improve tissue viability of nonhibernators. The model shows potential for in situ preservation of multiple organs in the cadaver.

View details for Web of Science ID A1976BF11100018

View details for PubMedID 1062190

Abstract

Twenty-seven anesthetized dogs were surface cooled at 4 to 6 degrees C. or 15 to 20 degrees C. Circulation was provided by the mechanical ventricular assist in 23 dogs. After 24 or 48 hours of in situ preservation, the kidneys were transplanted into the necks or iliac fossas of anephric recipients. Renal function was preserved in the cadaver for up to 48 hours at 15 to 20 degrees C. by maintaining a pulsatile circulation. Further cooling to 4 to 6 degrees C. caused progressive deterioration in renal function. The nonperfused kidneys kept in situ at 4 to 6 degrees C. did not produce any urine after transplantation. If the practical problems of total body cooling are solved, in situ preservation of multiple organs in the cadaver would increase the number of available organs for transplantation.

View details for Web of Science ID A1976BB71500011

View details for PubMedID 1108261

Abstract

Circulation was maintained in profoundly hypothermic dogs for 8 h at temperatures below 10 degrees C. During cooling to 5 degrees C cardiac output and blood pressure decreased and peripheral resistance rose. Thereafter, circulatory dynamics remained relatively stable over the next 6 h with a gradual decline in blood pressure. The proportion of blood flow to the heart and brain increased with cooling and remained elevated throughout the hypothermia period. Despite continued circulation, pulmonary edema developed after 5-7 h and the dogs were nonviable when rewarmed.

View details for Web of Science ID A1975AN92100005

View details for PubMedID 240278

View details for Web of Science ID A1974S943700012

View details for PubMedID 4208973

View details for Web of Science ID A1974V775600029

View details for PubMedID 4433010

View details for Web of Science ID A1974S553000014

View details for PubMedID 4816147

View details for PubMedID 4201982

View details for Web of Science ID A1973Q873400016

View details for PubMedID 4199737

View details for PubMedID 4806046

View details for Web of Science ID A1973P232000003

View details for PubMedID 4693921

View details for PubMedID 4209956

View details for Web of Science ID A1969C588400012

View details for PubMedID 5764211