Endothelial Cell Dysfunction in Pulmonary Hypertension

This study will examine and test healthy volunteers and patients with pulmonary hypertension to try to learn more about the disease and find better ways to detect, treat, and, if possible, slow progression. Pulmonary hypertension is a rare blood vessel disorder of the lung in which the pressure in the pulmonary artery (the blood vessel that leads from the heart to the lungs) rises above normal levels and may become life-threatening. Normal volunteers and patients with pulmonary hypertension 18 years of age and older may be eligible for this study. All candidates are screened with a review of their medical records. Normal volunteers also have a medical history, electrocardiogram, echocardiogram (heart ultrasound), and pulmonary function test, in which the subject breathes in and out of a tube that measures lung volume, mechanics and function. All participants undergo the following tests and procedures: * Echocardiogram to measure heart function and blood pressure in the lungs. A small probe held against the chest uses sound waves to obtain pictures of the heart. * Magnetic resonance imaging (MRI) to evaluate the heart's pumping action. Subjects lie on a stretcher that slides into a long, tube-shaped scanner. The machine uses a magnetic field and radio waves to obtain images of the heart. * 6-minute walk to measure how far the subject can walk in 6 minutes. Subjects walk around the hospital for 6 minutes at a comfortable pace. * Exercise testing to measure the ability to exercise and the subject's oxygen levels during exercise. Subjects exercise on a bike or treadmill while the oxygen and carbon dioxide they breathe are measured using a small device placed in the mouth. * Right heart catheterization to measure pressure in the heart and lungs. A small catheter (plastic tube) is placed in an arm vein. A longer catheter called a central line is placed in a deeper vein in the neck or just below the neck, or in the leg or arm. A long, thin catheter that measures blood p