129 Xenon Imaging in Patients Treated With Sotatercept

Who May Qualify: 1. Outpatients of either gender, Age 18-75 2. Diagnosis of precapillary PH (right heart catheterization demonstrating hemodynamic criteria of a mean pulmonary artery pressure (mPAP) ≥ 20 mmHg, pulmonary vascular resistance ≥ 5 WU, pulmonary capillary wedge pressure ≤ 15 mmHg) in the setting of Group 1 (PAH) 3. Willing and giving willing to sign a consent form and adhere to visit/protocol schedules (consent must be given before any study procedures are performed). 4. On a stable dose of background PAH therapy for \> 90 days prior to study enrollment 5. Women of childbearing potential must have a negative urine pregnancy test before MRI Who Should NOT Join This Trial: 1. Moderate to severe heart disease (LVEF \< 45%, Severe LV hypertrophy, Moderate to severe valvular disease) 2. Chronic thromboembolic disease 3. PH due to schistosomiasis 4. Active cancer 5. Sickle cell anemia 6. Prisoners and pregnant women will not be approached for the study 7. Conditions that will prohibit MRI scanning (metal in eye, claustrophobia, inability to lie supine) 8. Medical or psychological conditions which, in the opinion of the investigator, might create undue risk to the participant or interfere with the participant's ability to comply with the protocol requirements Always talk to your doctor about whether this trial is right for you.