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Protocol Number: 06-H-0165 
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 on the wrist and upper arm, and a strain gauge (a rubber band device) placed around the forearm. When the cuffs are inflated, blood flows into the arm, stretching the strain gauge, and the flow measurement is recorded. A small lamp is positioned over the hand to measure the light reflected from the hand and blood flow in the forearm. Blood samples are then drawn to measure blood counts and proteins and other natural body chemicals. Then, forearm blood flow is measured after administration of small doses of sodium nitroprusside, acetylcholine and L-NMMA. There is a 20- to 30-minute rest period between injections of the different drugs. In addition, HIV-infected patients with PAH undergo the following tests to determine the cause of their PAH: CT scan of the lungs, pulmonary function tests, 6-minute walk test, quality-of-life assessment, assessment of difficulty in breathing, exercise testing while measuring oxygen breathed in and carbon dioxide breathed out, blood tests, monitoring of oxygen saturation during sleep for 1 night and ventilation/perfusion scan. For the ventilation/perfusion scan, the subject breathes in a small amount of radioactive aerosol while images are obtained of the radioactivity as it enters the lungs, and then pictures of the lungs are taken from multiple angles. Next, the patient receives an injection of tiny particles of albumin (a protein) containing a small amount of radioactivity and pictures of the lungs are taken that show the pattern of blood flow to the lungs.
Patients with HIV and PAH who may benefit from the investigational drug, sildenafil (commonly known as Viagra), may continue to participate in the next stage of the study. They receive the first dose of sildenafil after completing the forearm blood flow study. They continue the drug for 16 weeks, returning to the clinic 1 week after the first dose and then every other week to monitor the response to treatment and drug side effects. At the end of 16 weeks, patients return to the clinic for a repeat evaluation, including blood tests, 6-minute walk test, echocardiogram, right heart catheterization and forearm blood flow study.
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National Institutes of Health Clinical Center