PI and sponsor will re-open study at new institution, will not transfer data due to COVID-19 situation

Pulmonary arterial hypertension(PAH) is associated with the development of right heart failure. In the setting of heart failure, the heart shifts to increasing dependence on glucose metabolism. In this study, the investigators will perform cardiac positron emission tomography/magnetic resonance imaging (PET/MRI) scans to measure glucose metabolism in the heart before and after initiation of pulmonary vasodilator therapy for pulmonary arterial hypertension.

Pulmonary arterial hypertension is associated with the development of right heart failure. In the setting of heart failure, the heart shifts to increasing dependence on glucose metabolism. In this study, the investigators will perform cardiac positron emission tomography/magnetic resonance imaging (PET/MRI) scans to measure glucose metabolism in the heart before and after initiation of pulmonary vasodilator therapy for pulmonary arterial hypertension. By utilizing a rest-exercise protocol and continuous PET imaging acquisition, we can capture real-time changes in glucose uptake in the heart in response to acute exercise. By coupling these measures of dynamic glucose utilization with MRI-based cardiac function, we will determine cardiac metabolic efficiency.

Inclusion Criteria:

• World Health Organization(WHO) group PAH secondary into idiopathic pulmonary arterial hypertension(IPAH) or connective tissue disease associated pulmonary arterial hypertension (CTDPAH)
• New York Heart Association (NYHA) classification I - III heart failure
• Vasodilator therapy naive
• Able to provide informed consent

Exclusion Criteria:

• Metabolic disorders such as uncontrolled diabetes (A1c > 8%) that may interfere with FDG uptake
• Baseline 6-minute walk distance (6MWD) < 400 feet or NYHA class IV heart failure
• Musculoskeletal abnormalities that would prevent exercise
• Contraindications to MRI

Patients with IPAH or CTD-PAH