Functional Pulmonary Capillary Surface Area in BPA for CTEPH

This study is measuring how the blood vessels in the lungs respond and recover after a procedure called balloon pulmonary angioplasty (BPA) — a treatment for chronic thromboembolic pulmonary hypertension (CTEPH), a condition where old blood clots narrow the lung's blood vessels and raise blood pressure in the lungs. Specifically, researchers will use an imaging technique to measure pulmonary capillary surface area before and after treatment. **You may be eligible if...** - You have chronic thromboembolic pulmonary hypertension (CTEPH) and have been approved to undergo balloon pulmonary angioplasty **You may NOT be eligible if...** - You are taking ACE inhibitors or angiotensin receptor blockers (ARBs), a common class of blood pressure medications - You have a patent foramen ovale (a small hole between the upper chambers of the heart that failed to close after birth) Talk to your doctor to see if this trial is right for you.