Aortic Dilatation in Endurance Athletes: A Physiologic and Mechanistic Study

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PROJECT SUMMARY / ABSTRACT The candidate recently joined the staff at Massachusetts General Hospital (MGH) in the Cardiovascular Performance Program (CPP), a unique group whose goals include conducting top-caliber human health and performance research. A core mission of the CPP is to use endurance athletes as a model through which to study the impacts of exercise on the cardiovascular system. This proposal applies this framework to evaluate in detail on the impact of exercise on the aorta. This proposal emerged from the dual observations that a) myocardial adaptation to exercise training is a well-established process that is felt to be adaptive rather than pathologic, while plasticity of the aorta has not been documented, and b) endurance athletes with aortic enlargement are commonly encountered in clinical practice. The candidate accordingly performed an initial study enrolling ~450 athletes and documenting an elevated prevalence of aortic dilatation in this population as compared to established population norms. This research proposal aims to define natural history, underlying physiology, and potential mechanisms underlying this phenotype of aortic dilation in endurance athletes, with the overarching goal of helping to establish whether this may represent an exercise-associated adaptation vs a novel form of overuse pathology. To achieve these goals, the applicant proposes to build off his prior work, leveraging the large cohort of athletes whom he enrolled into the initial study. Longitudinal follow-up will be performed on athlete subjects using echocardiography to mirror the index assessment. A subset will undergo detailed comparative physiologic phenotyping with cardiopulmonary exercise testing, advanced echocardiographic techniques including non-invasive evaluation of intracardiac and aortic blood flow patterns, vascular function profiling, and detailed anatomic imaging with computed tomography. Where possible, testing will be performed at rest and in response to physiologic provocation. Phenotypic profiles will be compared across athletes with and without aortic dilatation and control subjects with aortic dilatation to assess physiologic differences and potential mechanisms. Molecular evaluation will focus on plasma microRNA (miRNA), a class of molecules with well- established exercise responsiveness and known mechanistic associations with aortic disease, and circulating miRNA profiles will be assessed across these groups before and after exercise. The candidate’s career development plan includes advanced training in exercise physiology, cardiac imaging and physiologic phenotyping, translational science, and research methodology, all under the mentorship of a unique multidisciplinary team. The proposed science science will set the stage for future studies to assess clinical outcomes in this population and integrate additional translational study of exercise- associated aortic disease, which will form the basis of the candidate’s future R01 proposals. Over the course of the K23 award, the candidate’s goal is to develop into an independent clinical and translational investigator.