Research Projects

List of Research Projects

Ongoing Research

Children and Adolescents with Marfan Syndrome: 10,000 Healthy Steps and Beyond

The aim of this study is to encourage children and adolescents to walk at least 10,000 steps per day. To date, much emphasis has been placed on what sports activities these patients should avoid, due to disk or aortic dissection, rather than promoting regular physical activity. Thus, these patients commonly have sedentary lives due to self-imposed restrictions. This 6 month intervention entails weekly phone calls from the study team to encourage participants to make new goals and keep up their daily steps. Detailed records of daily steps will be collected via use of a fitness watch. Patients aged 10-19 will be recruited. Applanation tonometry, echocardiography, and blood work at study start and end will be used to determine differences in aortic health.

Population: Pediatric Marfan patients

Methods: Arterial tonometry, echocardiography, blood work

Pulse Wave Velocity in Infants Born to Diabetic Mothers

This study aims to determine whether maternal diabetes affects the arteries of newborn babies. A small non-invasive instrument, a tonometer, is used to measure pulse wave velocity (PWV), a measurement of how blood flows through a baby’s blood vessels. The PWV is obtained by a touch of the pen at different parts of the vessel, measuring how quickly the blood travels. An ultrasound is also used to look at the main blood vessel in a baby’s abdomen (the aorta) and measure the thickness of the wall. Lower PWV and smaller aortic thickness are both signs of healthier arteries. By measuring cardiovascular health of 90 newborns, the study’s objective, to find links between diabetic mothers and the arterial stiffness in their babies, will hopefully be met.

Population: Infants born to diabetic mothers

Methods: Arterial tonometry, abdominal aorta ultrasound

Endothelial Function in Pediatric D-looped TGA Patients after Arterial Switch Operation

Because of an increase in shear stress, D-looped TGA patients who have undergone switch operations are at increased risk of coronary artery disease. Using endothelial pulse amplitude testing (Endo-PAT) to asses arterial endothelial function, this study hypothesizes that abnormal endothelial function will be found in adolescent D-looped TGA patients who have undergone arterial switch operation. Endo-PAT is a non-invasive, reproducible technique that uses a thimble-like probe on the subject’s fingertips to measure the health of the subject’s arteries. Endothelial function measurements will be taken from both healthy subjects and D-looped TGA patients, then compared. 

Population: Patients with a history of transposition of the great arteries (a congenital heart defect)

Methods: Endothelial function testing

Vascular Function After Repair of Coarctation of the Aorta

Coartation of the aorta (CoA), a narrowing of the proximal descending aorta, is a common heart defect occurring in 6-8% of patients with congenital heart disease. Several techniques are used to repair this anomaly – surgical correction, the insertion of a stent, and using a balloon catheter to dilate the region of narrowing. All techniques are equally successful at correcting CoA, but vary with regard to how well they preserve vascular function in patients over the long term. Using several methods of measuring vascular health, the study will compare patients’ vascular/endothelial function some time after these three different methods for repairing CoA were performed. This study also aims to measure differences in patients’ blood pressures when responding to exercise after the three different treatments for CoA, as well as to explore various biomarkers as indicators of vascular function in the three different treatments.

Population: Patients with a history of coarctation of the aorta (a congenital heart defect)

Methods: Arterial tonometry, endothelial function testing, MRI, functional capacity, biomarkers analysis, 24-hour blood pressure monitoring

Funding Source: Liga de Amigos do Hospital Santa Marta

Completed Research

Improving Vascular Health in Pediatric Heart Transplant Recipients Using a Live Video Diet and Exercise Intervention

The aim of this study is to evaluate the feasibility and efficacy of a live video diet and exercise program on the vascular and functional health of pediatric heart transplant recipients. Since pediatric heart transplant recipients are at an increased risk for coronary arteriopathy that leads to significant morbidity and mortality late after heart transplantation, vascular health is very important. The twelve-week intervention will consist of three-times-weekly videoconference sessions with an exercise trainer for 45-60 minute sessions. Detailed food records will be kept for 5 of 7 days per week and will be reported to a nutrition counselor once a week. Patients aged 9-19 years will be recruited. Endothelial function (endoPAT) analysis, applanation tonometry, carotid artery imaging, exercise testing and blood work will be used to determine differences in vascular health.

Population: Pediatric heart transplant recipients

Methods: Arterial tonometry, endothelial function testing, carotid artery ultrasound, functional capacity

Maternal Arterial Stiffness and Fetal Health

The purpose of this study is to determine if there is a relationship between the stiffness of a mother’s arteries and the cardiovascular health of her fetus. Ultrasounds and echocardiography will be used to assess fetal cardiovascular health, and a pen-shaped pressure sensor will be used to assess variations in the blood pressure pulse wave in the maternal artery.  If there is abnormal feto-placental and cardiovascular health as a result of abnormal maternal arterial stiffness, there may be implications for maternal screening and management. Results from this study may include better control of the risk factors associated with increased arterial stiffness in pregnant women. Age range of the expected 76 participants will be between 18-40 years old – gender of fetuses and ethnic background will be random.

Population: Pregnant women and their fetuses

Methods: Fetal ultrasound, arterial tonometry

Live Video Diet and Exercise Intervention in Overweight Youth

This study evaluated the feasibility and impact of a live video lifestyle intervention on vascular and functional health in overweight adolescents. The twelve-week intervention consisted of three-times-weekly videoconference sessions with a trainer as well as weekly diet consultations. Vascular health indices including pulse wave velocity (PWV), augmentation index (AIx), reactive hyperemia index (RHI) and carotid artery stiffness were obtained at baseline at at the end of the study. Twenty overweight adolescents aged 14.5±2.1 years were enrolled, of which 17 completed the intervention. Significant changes in waist-hip ratio and lower density lipoprotein cholesterol levels, volume of inspired oxygen per heartbeat at peak exercise and functional movement score were all observed. In conclusion, the live video intervention promoted excellent adherence and improvement of both vascular and functional health of overweight adolescents.

Population: Overweight and obese adolescents

Methods: Arterial tonometry, endothelial function testing, carotid artery ultrasound, functional capacity

Papers/Presentations: Poster presented at Society for Vascular Medicine 2014 Annual Meeting and Scientific Sessions, June 12-14, 2014.

Funding: Supported with a grant from the Child Health Research Institute, Lucile Packard Foundation for Children’s Health, Stanford Clinical and Translational Science Award (grant number UL1 RR025744) and American Council on Exercise (San Diego, CA)

Maternal and Neonatal Factors Associated with Arterial Stiffness and Aortic Intima-medial Thickness in Healthy Term Neonates

While well validated in adults, peripheral arterial tonometry has not been applied to neonates. The objective of this study was to examine the feasibility of pulse wave velocity (PWV) among healthy term neonates as well as to evaluate the effects of perinatal factors on neonatal PWV. In this study, pregnant women with singleton gestation presenting for routine care were enrolled – postnatally, PWV measurements of the neonates were obtained using an arterial tonometer. The results of this study show that neonatal PWV by peripheral arterial tonometry is feasible and reproducible. The study also found an important association between increased maternal Hemoglobin A1c and neonatal PWV.

Population: Healthy term neonates

Methods: Arterial tonometry, abdominal aorta artery ultrasound

Papers/Presentations: Paper published in Neonatology

Carotid Artery Intima-Media Thickness Measurements in Children and Adolescents

This study analyzed the reproducibility of Carotid Artery Intima-Media Thickness (CIMT) measurements in youth using two different measurement techniques. CIMT is a noninvasive modality used to evaluate the presence of atherosclerosis. Carotid artery images from 184 subjects (mean age 14.7±2.2 years) were analyzed. These images were originally obtained as a component of a research study in Kawasaki syndrome completed at Boston Children's Hospital, and retrospectively analyzed for this study. Both measurement methods studied have excellent reproducibility. The reproducibility of pediatric CIMT measurements compares extremely favorably with that of other cardiovascular ultrasound measurements.

Population: Healthy children and adolescents

Methods: Carotid artery ultrasound

Papers/Presentations: Paper published in the Journal of the American Society of Echocardiography

Funding: Supported by the American Heart Association, National Scientist Development Award, and the Farb and McCance Family Funds. 

Vascular Health of Kawasaki Disease Patients

The objective of this study was to compare the indices of vascular health in Kawasaki Disease (KD) patients to that of control subjects. The study was made up of 203 patients aged 11-29 with KD onset of greater than 12 months and 50 healthy control subjects. Subjects were recruited and tested at Boston Children's Hospital. Endothelial function (EndoPAT-Index), intima-media thickness (IMT) of right and left common carotid arteries (RCCA and LCCA), fasting lipid-profile and C-reactive protein (CRP) were measured in order to assess vascular health. It was discovered that in contrast to some earlier reports, the study in North American children and young adults demonstrated that KD patients whose maximum coronary artery dimensions were either always normal or mildly ectatic have normal vascular health indices. These findings provide reassurance regarding peripheral vascular health in KD patients.

Population: Patients with a history of Kawasaki Disease

Methods: Arterial tonometry, endothelial function testing, carotid artery ultrasound

Papers/Presentations: Paper published in Journal of the American College of Cardiology

Funding: Supported by the American Heart Association, National Scientist Development Award, and the Farb and McCance Family Funds. 

Reproducibility and Feasibility of Arterial Tonometry in Children and Adolescents

The objective of this study was to prospectively test the feasibility and temporal reproducibility of arterial applanation tonometry in 40 child and adolescent subjects aged 10-19 years. Visits were separated by a mean of 3.08 +/- 3.7 days. The study found that arterial applanation tonometry is feasible and reproducible in healthy children and adolescents. Augmentation index has excellent intervisit reproducibility, whereas the intervisit reproducibility of pulse wave velocity relies on acquisition of multiple measurements that meet quality criteria established for adults.

Population: Healthy children and adolescents

Methods: Arterial tonometry

Papers/Presentations: Paper published in American Journal of Hypertension