Current Role at Stanford
Education & Certifications
Master of Public Health, University of Washington, Epidemiology (2011)
Bachelor of Science, Georgia Institute of Technology, Science, Technology and Culture (2004)
Despite the importance of the renin-angiotensin (Ang) system in abdominal aortic aneurysm (AAA) pathogenesis, strategies targeting this system to prevent clinical aneurysm progression remain controversial and unproven. We compared the relative efficacy of two Ang II type 1 receptor blockers, telmisartan and irbesartan, in limiting experimental AAAs in distinct mouse models of aneurysm disease.AAAs were induced using either 1) Ang II subcutaneous infusion (1000 ng/kg/min) for 28 days in male ApoE(-/-) mice, or 2) transient intra-aortic porcine pancreatic elastase infusion in male C57BL/6 mice. One week prior to AAA creation, mice started to daily receive irbesartan (50 mg/kg), telmisartan (10 mg/kg), fluvastatin (40 mg/kg), bosentan (100 mg/kg), doxycycline (100 mg/kg) or vehicle alone. Efficacy was determined via serial in vivo aortic diameter measurements, histopathology and gene expression analysis at sacrifice. Aortic aneurysms developed in 67% of Ang II-infused ApoE(-/-) mice fed with standard chow and water alone (n = 15), and 40% died of rupture. Strikingly, no telmisartan-treated mouse developed an AAA (n = 14). Both telmisartan and irbesartan limited aneurysm enlargement, medial elastolysis, smooth muscle attenuation, macrophage infiltration, adventitial neocapillary formation, and the expression of proteinases and proinflammatory mediators. Doxycycline, fluvastatin and bosentan did not influence aneurysm progression. Telmisartan was also highly effective in intra-aortic porcine pancreatic elastase infusion-induced AAAs, a second AAA model that did not require exogenous Ang II infusion.Telmisartan suppresses experimental aneurysms in a model-independent manner and may prove valuable in limiting clinical disease progression.
View details for DOI 10.1371/journal.pone.0049642
View details for Web of Science ID 000312104700009
View details for PubMedID 23226500
In addition to increased risks for aneurysm-related death, previous studies have determined that all-cause mortality in abdominal aortic aneurysm (AAA) patients is excessive and equivalent to that associated with coronary heart disease. These studies largely preceded the current era of coronary heart disease risk factor management, however, and no recent study has examined contemporary mortality associated with early AAA disease (aneurysm diameter between 3 and 5 cm). As part of an ongoing natural history study of AAA, we report the mortality risk associated with presence of early disease.Participants were recruited from three distinct health care systems in Northern California between 2006 and 2011. Aneurysm diameter, demographic information, comorbidities, medication history, and plasma for biomarker analysis were collected at study entry. Survival status was determined at follow-up. Data were analyzed with t-tests or ?(2) tests where appropriate. Freedom from death was calculated via Cox proportional hazards modeling; the relevance of individual predictors on mortality was determined by log-rank test.The study enrolled 634 AAA patients; age 76.4 ± 8.0 years, aortic diameter 3.86 ± 0.7 cm. Participants were mostly male (88.8%), not current smokers (81.6%), and taking statins (76.7%). Mean follow-up was 2.1 ± 1.0 years. Estimated 1- and 3-year survival was 98.2% and 90.9%, respectively. Factors independently associated with mortality included larger aneurysm size (hazard ratio, 2.12; 95% confidence interval, 1.26-3.57 for diameter >4.0 cm) and diabetes (hazard ratio, 2.24; 95% confidence interval, 1.12-4.47). After adjusting for patient-level factors, health care system independently predicted mortality.Contemporary all-cause mortality for patients with early AAA disease is lower than that previously reported. Further research is warranted to determine important factors that contribute to improved survival in early AAA disease.
View details for DOI 10.1016/j.jvs.2012.04.023
View details for Web of Science ID 000310428200007
View details for PubMedID 22832264
No effective medical therapy exists for early abdominal aortic aneurysm (AAA) disease. Lower extremity exercise improves aortic hemodynamics and reduces inflammation, but the safety and efficacy of exercise training in AAA disease is unknown. As an interim analysis of our prospective, randomized, longitudinal trial of exercise for AAA suppression, we investigated whether subjects with early disease could safely achieve target metabolic and hemodynamic goals.One hundred eight participants were randomized to exercise training (EX) or usual care (UC). EX subjects participated in a combination of in-house and home exercise training, with efforts directed toward moderate daily exercise participation. Comparisons were made between EX and UC subjects who completed 1 year of follow-up (n = 26 and 31, respectively, mean age 72 ± 8 years). EX and UC groups were compared for safety, cardiopulmonary exercise test responses, weekly energy expenditure, and biometric indices.No paradoxical increase in AAA growth rate or adverse clinical events occurred as a consequence of exercise training. EX participants expended an average of 2269 ± 1207 kcal/wk and increased exercise capacity (42% increase in treadmill time, 24% increase in estimated metabolic equivalents, P = .01 and .08 between groups, respectively). EX participants demonstrated a significant reduction in C-reactive protein and tended to reduce waist circumference and waist-to-hip ratio (P = .06 and .07, respectively).Preliminary analyses suggest that exercise training is well tolerated and sustainable in small AAA subjects over 1 year. Despite age and comorbidities, exercising AAA subjects achieve meaningful exercise targets and significantly modify activity-dependent variables.
View details for DOI 10.1097/HCR.0b013e3181ebf2db
View details for Web of Science ID 000284060500003
View details for PubMedID 20724934
Abdominal aortic aneurysm (AAA) disease is a prevalent and highly morbid condition among older people in the US. There are currently no proven methods for reducing or eliminating enlargement in smaller preclinical aneurysms. Given their relatively slow increase in diameter (typically <0.4 cm/year), these smaller aneurysms offer a valuable window into the underlying pathophysiology of AAA disease. Through a Vascular Remodeling Specialized Center of Clinically Oriented Research program funded by the National Institutes of Health, we have established, in conjunction with Northern California Kaiser Permanente, a multidisciplinary research effort to efficiently identify and handicap suppressive therapeutic strategies for early AAA disease.
View details for PubMedID 21364806
View details for Web of Science ID 000293814400078