Sildenafil to Treat HIV-Associated Pulmonary Hypertension

This study will examine how blood pressure in the lungs is controlled in healthy people, people with HIV and people with HIV and pulmonary artery hypertension (high blood pressure in the lungs, also called PAH). PAH sometimes develops in people with HIV, but it is not known why this occurs or how best to treat it. Healthy volunteers and patients with HIV infection who are 18 years of age or older may be eligible for this study. All candidates are screened with a medical history, physical examination, electrocardiogram (EKG), chest x-ray, echocardiogram and blood tests. Participants undergo the following procedures: All participants have a right heart catheterization and forearm blood flow study. * Catheterization study. A catheter (plastic tube) is placed in an arm vein and possibly in an artery in the arm. Then a large catheter is passed through a vein in the groin, neck or chest. Through this "introducer" catheter, another catheter is advanced into the right side of the heart and to the pulmonary artery. A facemask is put in place to measure the amount of nitric oxide produced by the lungs. Acetylcholine is infused through the catheter and its effects on blood pressure in the lungs and on the amount of nitric oxide exhaled is measured. After about 1 hour, the catheter and facemask are removed and a new catheter is inserted through the introducer catheter into the pulmonary artery. The subject is moved into an MRI scanner where blood flow is measured after infusion of three different medications: acetylcholine (causes blood vessels to expand and slows heart rate); sodium nitroprusside (causes blood vessels to expand and increases blood flow to the heart); and L-NMMA (decreases blood flow by blocking production of nitric oxide in cells lining the blood vessels). * Blood flow study. Small tubes are inserted into the artery of the patient's forearm. These are used to infuse medicines and draw blood samples. Forearm blood flow is measured using pressure cuffs placed