Understanding the Effects of Pulmonary Arterial Hypertension on Lean Muscle Mass

Patients with pulmonary arterial hypertension (PAH) are at increased risk of muscle loss and decreased physical activity. This study will aim to (1) understand the way in which muscle loss occurs in PAH, particularly the role of fat surrounding the heart, and (2) look at the impact muscle loss has on quality of life, daily physical activity, and hospitalizations in patients with PAH. The findings from this study could help identify potentially treatable factors that may improve the overall quality of life and physical functioning of patients with PAH. Subjects will be asked to attend a baseline visit where the following will be performed: * Measure your vital signs * Undergo a research blood draw, less than 4 tablespoons * Provide a urine pregnancy test (if applicable) * Review demographics, personal history, and medical history * Review current PAH medications * Complete questionnaires on how your PAH affects you * Complete a test of physical performance * Complete a grip strength test * Undergo an echocardiogram (Echo) * Complete a six-minute walk test * Undergo a Chest CT Scan * Undergo a scan of your body composition (DXA scan) * Obtain a weight and body composition measurement on the InBody Scale Subjects will also complete activity moniotring, two 24-hour diet recalls, and participate in remote follow-up visits every 6 months