MD, Columbia University, College of Physicians and Surgeons, Medicine (2015)
BA, Harvard University, Molecular and Cellular Biology, Music (2011)
Precision surgery: patient-specific bypass grafting and valve repair strategies
Autonomous robotic surgery
Photosynthetic therapies to circumvent myocardial ischemia
Collateral artery formation as protection against myocardial infarction
Angiogenesis and myocardial regeneration to prevent heart failure
Tissue engineering to limit ventricular remodeling
Understanding the biomechanics of injured and failing hearts
View details for PubMedID 30683833
Collateral arteries are an uncommon vessel subtype that can provide alternate blood flow to preserve tissue following vascular occlusion. Some patients with heart disease develop collateral coronary arteries, and this correlates with increased survival. However, it is not known how these collaterals develop or how to stimulate them. We demonstrate that neonatal mouse hearts use a novel mechanism to build collateral arteries in response to injury. Arterial endothelial cells (ECs) migrated away from arteries along existing capillaries and reassembled into collateral arteries, which we termed "artery reassembly". Artery ECs expressed CXCR4, and following injury, capillary ECs induced its ligand, CXCL12. CXCL12 or CXCR4 deletion impaired collateral artery formation and neonatal heart regeneration. Artery reassembly was nearly absent in adults but was induced by exogenous CXCL12. Thus, understanding neonatal regenerative mechanisms can identify pathways that restore these processes in adults and identify potentially translatable therapeutic strategies for ischemic heart disease.
View details for PubMedID 30686582
Adverse remodeling of the left ventricle (LV) after myocardial infarction (MI) results in abnormal tissue biomechanics and impaired cardiac function, often leading to heart failure. We hypothesized that intramyocardial delivery of engineered stromal cell-derived factor 1? analog (ESA), our previously-developed supra-efficient pro-angiogenic chemokine, preserves biaxial LV mechanical properties after MI. Male Wistar rats (n?=?45) underwent sham surgery (n?=?15) or permanent left anterior descending coronary artery ligation. Rats sustaining MI were randomized for intramyocardial injections of either saline (100??L, n?=?15) or ESA (6??g/kg, n?=?15), delivered at four standardized borderzone sites. After 4 weeks, echocardiography was performed, and the hearts were explanted. Tensile testing of the anterolateral LV wall was performed using a displacement-controlled biaxial load frame, and modulus was determined after constitutive modeling. At 4 weeks post-MI, compared to saline controls, ESA-treated hearts had greater wall thickness (1.68?±?0.05?mm vs 1.42?±?0.08?mm, p?=?0.008), smaller end-diastolic LV internal dimension (6.88?±?0.29?mm vs 7.69?±?0.22?mm, p?=?0.044), and improved ejection fraction (62.8?±?3.0% vs 49.4?±?4.5%, p?=?0.014). Histologic analysis revealed significantly reduced infarct size for ESA-treated hearts compared to saline controls (29.4?±?2.9% vs 41.6?±?3.1%, p?=?0.021). Infarcted hearts treated with ESA exhibited decreased modulus compared to those treated with saline in both the circumferential (211.5?±?6.9?kPa vs 264.3?±?12.5?kPa, p?=?0.001) and longitudinal axes (194.5?±?6.5?kPa vs 258.1?±?14.4?kPa, p?0.001). In both principal directions, ESA-treated infarcted hearts possessed similar tissue compliance as sham non-infarcted hearts. Overall, intramyocardial ESA therapy improves post-MI ventricular remodeling and function, reduces infarct size, and preserves native LV biaxial mechanical properties.
View details for PubMedID 31035067
Cardiovascular bypass grafting is an essential treatment for complex cases of atherosclerotic disease. Because the availability of autologous arterial and venous conduits is patient-limited, self-assembled cell-only grafts have been developed to serve as functional conduits with off-the-shelf availability. The unacceptably long production time required to generate these conduits, however, currently limits their clinical utility. Here, we introduce a novel technique to significantly accelerate the production process of self-assembled engineered vascular conduits.Human aortic smooth muscle cells and skin fibroblasts were used to construct bilevel cell sheets. Cell sheets were wrapped around a 22.5-gauge Angiocath needle to form tubular vessel constructs. A thin, flexible membrane of clinically approved biodegradable tissue glue (Dermabond Advanced) served as a temporary, external scaffold, allowing immediate perfusion and endothelialization of the vessel construct in a bioreactor. Subsequently, the matured vascular conduits were used as femoral artery interposition grafts in rats (n=20). Burst pressure, vasoreactivity, flow dynamics, perfusion, graft patency, and histological structure were assessed.Compared with engineered vascular conduits formed without external stabilization, glue membrane-stabilized conduits reached maturity in the bioreactor in one-fifth the time. After only 2 weeks of perfusion, the matured conduits exhibited flow dynamics similar to that of control arteries, as well as physiological responses to vasoconstricting and vasodilating drugs. The matured conduits had burst pressures exceeding 500 mm?Hg and had sufficient mechanical stability for surgical anastomoses. The patency rate of implanted conduits at 8 weeks was 100%, with flow rate and hind-limb perfusion similar to those of sham controls. Grafts explanted after 8 weeks showed a histological structure resembling that of typical arteries, including intima, media, adventitia, and internal and external elastic membrane layers.Our technique reduces the production time of self-assembled, cell sheet-derived engineered vascular conduits to 2 weeks, thereby permitting their use as bypass grafts within the clinical time window for elective cardiovascular surgery. Furthermore, our method uses only clinically approved materials and can be adapted to various cell sources, simplifying the path toward future clinical translation.
View details for PubMedID 30474423
Scimitar syndrome involves congenital anomalous pulmonary venous return to the inferior vena cava. Optimal management remains controversial. We describe the natural history of disease, nonsurgical and surgical outcomes, and risk factors for poor outcomes at our institution.Patients with anomalous pulmonary venous return to the inferior vena cava documented on echocardiography at our institution between January 1994 and January 2015 were reviewed retrospectively. The study protocol IRB-AAAO1805 was approved.Forty-seven patients were identified, including 20 infants with significant associated congenital heart defects (42.6%, including 7 with single ventricle physiology), and 10 infants (21.3%) and 16 noninfants (34.0%) with isolated scimitar syndrome. Median follow-up was 3.55 years. Noninfants exhibited lower incidences of right pulmonary artery hypoplasia (p < 0.001), aortopulmonary collaterals (p = 0.004), and scimitar vein obstruction at the caval confluence (p = 0.032). Eighteen patients (38.3%) underwent surgical repair for scimitar syndrome. Overall mortality after baffle repair or scimitar vein reimplantation was 37.5% (3 of 8) for infants and 0% (0 of 6) for noninfants (p = 0.209). Overall mortality for medically managed infants was 46.7% (7 of 15) compared with 0% (0 of 8) for noninfants (p = 0.052). Multivariable analyses identified infantile onset as an independent risk factor for stenosis or obstruction after repair (hazard ratio 9.34, p = 0.048), and single ventricle physiology as an independent risk factor for mortality among unrepaired patients (hazard ratio 29.8, p = 0.004).The severity of scimitar syndrome depends on presenting age and associated congenital heart disease. Nonsurgical and surgical outcomes are suboptimal for infantile disease, which is a risk factor for stenosis after repair. Single ventricle physiology is associated with poor prognosis.
View details for DOI 10.1016/j.athoracsur.2017.06.061
View details for PubMedID 29054305
BACKGROUND: Neochordoplasty is an important repair technique, though optimal anchoring position is unknown. While typically anchored at papillary muscles, new percutaneous devices anchor the chordae at or near the ventricular apex, which may have an effect on chordal forces and the long-term durability of the repair.METHODS: Porcine mitral valves (n=6) were mounted in a left heart simulator that generates physiological pressure and flow through the valves while chordal forces were measured using Fiber Bragg Grating strain gauge sensors. Isolated mitral regurgitation was induced by cutting P2 primary chordae and the regurgitant valve was repaired using PTFE neochord with apical anchoring, followed by papillary muscle fixation for comparison. In both cases, the neochord was anchored to a customized force-sensing post positioned to mimic the relevant in vivo placement.RESULTS: Echocardiographic and hemodynamic data confirmed that the repairs restored physiologic hemodynamics. Forces on the chordae and neochord were lower for papillary fixation than the apical (p=0.003). Additionally, the maximum rate of change of force was higher for the chordae and neochord for apical fixation when compared to papillary (p=0.028).CONCLUSIONS: Apical point of anchoring results in higher forces on the chordae and neochord stitch as well as an increased rate of loading on the neochord when compared to the papillary muscle fixation. These results suggest the papillary fixation repair may have superior durability.
View details for PubMedID 30836099
Hydrogels have emerged as a diverse class of biomaterials offering a broad range of biomedical applications. Specifically, injectable hydrogels are advantageous for minimally invasive delivery of various therapeutics and have great potential to treat a number of diseases. However, most current injectable hydrogels are limited by difficult and time-consuming fabrication techniques and are unable to be delivered through long, narrow catheters, preventing extensive clinical translation. Here, the development of an easily-scaled, catheter-injectable hydrogel utilizing a polymer-nanoparticle crosslinking mechanism is reported, which exhibits notable shear-thinning and self-healing behavior. Gelation of the hydrogel occurs immediately upon mixing the biochemically modified hyaluronic acid polymer with biodegradable nanoparticles and can be easily injected through a high-gauge syringe due to the dynamic nature of the strong, yet reversible crosslinks. Furthermore, the ability to deliver this novel hydrogel through a long, narrow, physiologically-relevant catheter affixed with a 28-G needle is highlighted, with hydrogel mechanics unchanged after delivery. Due to the composition of the gel, it is demonstrated that therapeutics can be differentially released with distinct elution profiles, allowing precise control over drug delivery. Finally, the cell-signaling and biocompatibility properties of this innovative hydrogel are demonstrated, revealing its wide range of therapeutic applications.
View details for PubMedID 30714355
Orthotopic heart transplantation with concomitant aortic surgery is rarely performed. Herein, we describe the successful management of a patient with an otherwise inoperable, ruptured aortic root pseudoaneurysm using combined cardioaortic replacement under hypothermic circulatory arrest.
View details for PubMedID 30608529
Few technologies exist that can provide quantitative data on forces within the mitral valve apparatus. Marker-based strain measurements can be performed, but chordal geometry and restricted optical access are limitations. Foil-based strain sensors have been described and work well, but the sensor footprint limits the number of chordae that can be measured. We instead utilized Fiber Bragg Grating (FBG) sensors-optical strain gauges made of 125µm diameter silica fibers- to overcome some limitations of previous methods of measuring chordae tendineae forces. Using FBG sensors, we created a force-sensing neochord that mimics the natural shape and movement of native chordae. FBG sensors reflect a specific wavelength of light depending on the spatial period of gratings. When force is applied, the gratings move relative to one another, shifting the wavelength of reflected light. This shift is directly proportional to force applied. The FBG sensors were housed in a protective sheath fashioned from a 0.025" flat coil, and attached to the chordae using polytetrafluoroethylene suture. The function of the force-sensing neochordae was validated in a 3D-printed left heart simulator, which demonstrated that FBG sensors provide highly sensitive force measurements of mitral valve chordae at a temporal resolution of 1000 Hz. As ventricular pressures increased, such as in hypertension, chordae forces also increased. Overall, FBG sensors are a viable, durable, and high-fidelity sensing technology that can be effectively used to measure mitral valve chordae forces and overcome some limitations of other such technologies.
View details for DOI 10.1115/1.4044142
View details for PubMedID 31253992
BACKGROUND: Studies assessing the safety and effectiveness of Del Nido cardioplegia for adult cardiac surgery remain limited. We investigated early outcomes after coronary artery bypass grafting (CABG) using single-dose Del Nido cardioplegia vs. conventional multi-dose blood cardioplegia. Methods?and?Results: The 81 consecutive patients underwent isolated CABG performed by a single surgeon. The initial 27 patients received anterograde blood cardioplegia, while the subsequent 54 patients received anterograde Del Nido cardioplegia. There were no differences in the baseline characteristics of each group nor any differences in the 30-day incidences of myocardial infarction, all-cause death, and readmission following surgery. The use of Del Nido cardioplegia was associated with shorter cardiopulmonary bypass time (98 vs. 115 min, P=0.011), shorter cross-clamp time (74 vs. 87 min, P=0.006), and decreased need for intraoperative defibrillation (13.0% vs. 33.3%, P=0.030) compared with blood cardioplegia. To control for the difference in cross-clamp time, we performed propensity score matching with a logistical treatment model and confirmed that Del Nido cardioplegia provided similar outcomes as blood cardioplegia and also reduced the need for defibrillation independent of cross-clamp time.CONCLUSIONS: Compared with conventional blood cardioplegia, Del Nido cardioplegia provided excellent myocardial protection with reduced need for intraoperative defibrillation, shorter bypass and cross-clamp times, and comparable early clinical outcomes for adult patients undergoing CABG.
View details for PubMedID 30531128
OBJECTIVE: The optimal conduit for valve-sparing aortic root replacement is still debated, with several conduit variations available, ranging from straight tubular grafts to Valsalva grafts. Benefits of neosinus reconstruction include enhanced flow profiles and improved hemodynamics. Curiously, however, some clinical data suggest that straight grafts may have greater long-term durability. In this study, we hypothesized that straight tubular grafts may help maintain the native cylindrical position of the aortic valve commissures radially, resulting in preserved leaflet coaptation, reduced stresses, and potentially improved valve performance.METHODS: Using 3D printing, a left heart simulator with a valve-sparing root replacement model and a physiologic coronary circulation was constructed. Aortic valves were dissected from fresh porcine hearts and reimplanted into either straight tubular grafts (n=6) or Valsalva grafts (n=6). Conduits were mounted into the heart simulator and hemodynamic, echocardiographic, and high-speed videometric data were collected.RESULTS: Hemodynamic parameters and coronary blood flow were similar between straight and Valsalva grafts, although the former were associated with lower regurgitant fractions, less peak intercommissural radial separation, preserved leaflet coaptation, decreased leaflet velocities, and lower relative leaflet forces compared with Valsalva grafts.CONCLUSIONS: Valsalva grafts and straight grafts perform equally well in terms of gross hemodyanics and coronary blood flow. Interestingly, however, the biomechanics of these 2 conduits differ considerably, with straight grafts providing increased radial commissural stability and leaflet coaptation. Further investigation into how these parameters influence clinical outcomes is warranted.
View details for PubMedID 30745047
View details for PubMedID 29317089
View details for PubMedID 29576264
Whether a second arterial conduit improves outcomes after multivessel coronary artery bypass grafting remains unclear. Consequently, arterial conduits other than the left internal thoracic artery are seldom used in the United States.Using a state-maintained clinical registry including all 126 nonfederal hospitals in California, we compared all-cause mortality and rates of stroke, myocardial infarction, repeat revascularization, and sternal wound infection between propensity score-matched cohorts who underwent primary, isolated multivessel coronary artery bypass grafting with the left internal thoracic artery, and who received a second arterial conduit (right internal thoracic artery or radial artery, n=5866) or a venous conduit (n=53?566) between 2006 and 2011. Propensity score matching using 34 preoperative characteristics yielded 5813 matched sets. A subgroup analysis compared outcomes between propensity score-matched recipients of a right internal thoracic artery (n=1576) or a radial artery (n=4290).Second arterial conduit use decreased from 10.7% in 2006 to 9.1% in 2011 (P<0.0001). However, receipt of a second arterial conduit was associated with significantly lower mortality (13.1% versus 10.6% at 7 years; hazard ratio, 0.79; 95% confidence interval [CI], 0.72-0.87), and lower risks of myocardial infarction (hazard ratio, 0.78; 95% CI, 0.70-0.87) and repeat revascularization (hazard ratio, 0.82; 95% CI, 0.76-0.88). In comparison with radial artery grafts, right internal thoracic artery grafts were associated with similar mortality rates (right internal thoracic artery 10.3% versus radial artery 10.7% at 7 years; hazard ratio, 1.10; 95% CI, 0.89-1.37) and individual risks of cardiovascular events, but the risk of sternal wound infection was increased (risk difference, 1.07%; 95% CI, 0.15-2.07).Second arterial conduit use in California is low and declining, but arterial grafts were associated with significantly lower mortality and fewer cardiovascular events. A right internal thoracic artery graft offered no benefit over that of a radial artery, but did increase risk of sternal wound infection. These findings suggest surgeons should consider lowering their threshold for using arterial grafts, and the radial artery may be the preferred second conduit.
View details for PubMedID 29242351
Diabetes mellitus is a risk factor for coronary artery disease and diabetic cardiomyopathy, and adversely impacts outcomes following coronary artery bypass grafting. Current treatments focus on macro-revascularization and neglect the microvascular disease typical of diabetes mellitus-induced cardiomyopathy (DMCM). We hypothesized that engineered smooth muscle cell (SMC)-endothelial progenitor cell (EPC) bi-level cell sheets could improve ventricular dysfunction in DMCM.Primary mesenchymal stem cells (MSCs) and EPCs were isolated from the bone marrow of Wistar rats, and MSCs were differentiated into SMCs by culturing on a fibronectin-coated dish. SMCs topped with EPCs were detached from a temperature-responsive culture dish to create an SMC-EPC bi-level cell sheet. A DMCM model was induced by intraperitoneal streptozotocin injection. Four weeks after induction, rats were randomized into 3 groups: control (no DMCM induction), untreated DMCM, and treated DMCM (cell sheet transplant covering the anterior surface of the left ventricle).SMC-EPC cell sheet therapy preserved cardiac function and halted adverse ventricular remodeling, as demonstrated by echocardiography and cardiac magnetic resonance imaging at 8 weeks after DMCM induction. Myocardial contrast echocardiography demonstrated that myocardial perfusion and microvascular function were preserved in the treatment group compared with untreated animals. Histological analysis demonstrated decreased interstitial fibrosis and increased microvascular density in the SMC-EPC cell sheet-treated group.Treatment of DMCM with tissue-engineered SMC-EPC bi-level cell sheets prevented cardiac dysfunction and microvascular disease associated with DMCM. This multi-lineage cellular therapy is a novel, translatable approach to improve microvascular disease and prevent heart failure in diabetic patients.
View details for PubMedID 29096622
High-sensitivity C-reactive protein (hs-CRP) is independently associated with cardiovascular events in coronary artery disease (CAD) patients and reducing the hs-CRP level may further benefit this population. We conduct this parallel design, randomized-controlled trial to assess the effectiveness of adjunct sodium tanshinone IIA sulfate (STS) therapy on circulating inflammation markers in CAD patients. Unstable angina or non-ST-elevation myocardial infarction patients with increased hs-CRP level were randomly assigned to atorvastatin-based standard medical therapy or standard therapy plus STS injection (80?mg, once daily for 14 consecutive days). The primary outcome was hs-CRP level. After the 14-day treatment, the experimental group (n?=?35) exhibited significantly lower levels of hs-CRP than the control group (n?=?35) (1.72 vs 3.20?mg/L, p?=?0.0191). Lower levels of interleukin-6, monocyte chemotactic protein-1 (MCP-1), and soluble CD40 ligand were also observed in the experimental group. Angina symptoms were also better controlled in the experimental group. At 30 days after treatment completion, MCP-1 levels remained lower in the experimental group than in the control group (313.88 vs 337.91?pg/mL, p?=?0.0078). No serious adverse events occurred. Our study demonstrates that on the basis of standard medical therapy, STS further reduce elevated hs-CRP and other circulating inflammation markers in CAD patients. (Chictr.org number: ChiCTR-TRC-12002361).
View details for PubMedID 29234038
Prolonged allograft ischaemic time in heart transplantation adversely impacts the performance of the donor heart in the immediate postoperative period and ultimately results in decreased post-transplant survival. Therefore, optimal surgical technique for heart transplantation should aim to minimize allograft ischaemic time. Here, we report a case of successful orthotopic heart transplantation using a modified technique to reduce allograft ischaemic time and warm ischaemic time.
View details for PubMedID 29186382
Pediatric cardiac surgery, especially for small neonates, typically requires blood products to counter hemodilution during cardiopulmonary bypass. Children with congenital heart defects whose families adhere to faith-based proscriptions against blood transfusion therefore represent a challenging surgical population. Here, we report the case of a ten-day-old, 3.6-kg patient of Jehovah's Witness faith, who was diagnosed with unilateral pulmonary artery discontinuity, bilateral patent ductus arteriosus, and an otherwise structurally normal heart. Pulmonary artery reimplantation was successfully performed without giving blood products. This case adds to previous reports of successful bloodless cardiac surgery in neonates and describes the specific strategies that contributed to successful pulmonary artery reimplantation.
View details for DOI 10.1177/2150135115582071
View details for PubMedID 26715005
Delayed gastric emptying is a significant postoperative complication of living donor hepatectomy for liver transplantation and may require endoscopic or surgical intervention in severe cases. Although the mechanism of posthepatectomy delayed gastric emptying remains unknown, vagal nerve injury during intraoperative dissection and adhesion formation postoperatively between the stomach and cut liver surface are possible explanations. Here, we present the first reported case of delayed gastric emptying following fully laparoscopic hepatectomy for living donor liver transplantation. Additionally, we also present a case in which symptoms developed after open right hepatectomy, but for which dissection for left hepatectomy was first performed. Through our experience and these two specific cases, we favor a neurovascular etiology for delayed gastric emptying after hepatectomy.
View details for DOI 10.1155/2014/582183
View details for PubMedID 25610698
View details for PubMedCentralID PMC4291134
Background. Coronary heart disease (CHD) due to atherosclerotic inflammation remains a significant threat to global health despite the success of the lipid-lowering, anti-inflammatory statins. Tanshinone IIA, a potent anti-inflammatory compound derived from Traditional Chinese Medicine (TCM), may be able to supplement statins by further reducing levels of circulating inflammatory markers correlated to cardiovascular risk. Here, we present the protocol of a randomized controlled trial (RCT) that will investigate the synergistic effect of sodium tanshinone IIA sulfate and simvastatin on reducing elevated inflammatory markers in patients with CHD.Seventy-two inpatients with confirmed CHD, elevated serum high-sensitivity C-reactive protein (Hs-CRP) level, and a TCM diagnosis of blood stasis syndrome will be enrolled and randomized 1?:?1 into the control or experimental group. Intervention. All subjects will receive a standard Western therapy including 20?mg simvastatin orally once per evening. Patients in the experimental group will additionally receive a daily 80?mg dose of sodium tanshinone IIA sulfate intravenously, diluted into 250?mL 0.9% NaCl solution. The treatment period will be 14 days. Outcomes. Primary outcome parameter: serum Hs-CRP level. Secondary outcome parameters: other circulating inflammatory markers (including IL-6, TNF ? , VCAM-1, CD40, sCD40L, MCP-1, and MMP-9), improvement in symptoms of angina and blood stasis syndrome, and safety. This trial is registered with ChiCTR-TRC-12002361.
View details for DOI 10.1155/2013/756519
View details for Web of Science ID 000323265300001
View details for PubMedID 23983803
View details for PubMedCentralID PMC3747599