The Impact of Exercise-Induced Cardiac Remodeling on Myocardial Efficiency

The investigators anticipate that by defining the myocardial metabolic profiles of exercise-induced left ventricular hypertrophy (EI-LVH) and hypertrophic cardiomyopathy (HCM), we will determine if these differ sufficiently to distinguish these two forms of LVH. Because HCM causes sudden death with physical activity, it is critically important to determine the etiology of undifferentiated "gray zone" LVH in the athlete presenting for medical evaluation, and existing mechanisms of assessing myocardial structure and function are not universally adequate. The investigators anticipate that the work may translate into a novel clinical tool for differentiating pathology from physiology in "gray-zone" LVH. The complementary mechanistic goal of this study is to combine comprehensive evaluations of myocardial functional parameters and metabolism to better understand the link between function and metabolism and, ultimately, the biological mechanisms of EI-LVH and LVH due to HCM. There are three specific aims to the research study. The first specific aim is to define the relationships between changes in myocardial metabolic efficiency (MME) and changes in myocardial mechanics that accompany EI-LVH. The second is to establish and compare myocardial metabolic profiles of EI-LVH and HCM. The third is to analyze a subset of the endurance athlete subjects to determine the impact of aerobic exercise training on MME over a 90-day period. The study will employ a mixed study design. The study is a cross-sectional design but will analyze a subset of endurance athletes longitudinally with repeated measures after 90 days from the first three study visits. For the cross sectional design, the first study visit will be at Massachusetts General Hospital and will involve a cardiopulmonary exercise test (CPET) on an upright bicycle, with blood sampling before the CPET at rest, and after exercise. Study visits two and three will follow the same protocol. Both study visits two and three will occur at Brigham and Women's Hospital and will involve an echocardiogram and a positron emission tomography (PET) scan. Both visits will include blood sampling at rest, and then either the resting PET scan or a PET scan after acute exercise provocation on a supine bicycle. Study visits two and three will occur on two sequential mornings.