When someone says high blood pressure (hypertension), most people think of heart disease. However, a specific type of hypertension, called pulmonary arterial hypertension or PAH, affects the arteries in your lungs, but does not affect the arteries in the rest of the body.

The pulmonary arteries carry blood from the right ventricle of the heart into the lungs, where the blood picks up oxygen for delivery to the rest of the body. In normal lungs, the pulmonary arteries are flexible and look like a tree with many delicate branches. In PAH, the walls of the pulmonary arteries become thickened and constricted, resulting in an inadequate amount of oxygen delivered to the blood and much higher pressure in the pulmonary arteries than normal. As PAH progresses, many of the vessels become obstructed and resistance to blood flow through the lungs is increased, causing the right heart to work much harder. As a result of advanced PAH, right heart failure and death often occur.

There are two types of PAH: 1) the relatively rare, primary or idiopathic, which includes PAH of unknown cause that can be either sporadic or familial (inherited), and 2) the more common, secondary PAH found in association with other chronic lung and heart diseases. Primary PAH most commonly affects young women, but it can affect both genders regardless of age or race.

The symptoms of PAH include fatigue, dizziness, fainting, chest pains and difficulty in breathing. These symptoms are nonspecific and are a reason PAH is often undiagnosed or misdiagnosed. The most definitive diagnostic test is right heart catheterization. Treatment options for PAH have improved over the past several years and basic research is leading to better therapies.

The NHLBI supports a portfolio of nearly 80 research projects on PAH. This includes basic cell and molecular biology of PAH; identification of the gene(s) and gene mutations that predispose a person to develop PAH; and multi-disciplinary projects combining basic and patient-based research. Clinical research currently includes five clinical studies supported through investigator-initiated grants, and two clinical studies being conducted by the Division of Intramural Research. These clinical studies include trials of new therapies and diagnostic methods, as well as studies that examine the underlying mechanisms of PAH, secondary to scleroderma or sickle cell anemia, and pulmonary hypertension that occurs in newborn babies.

For more information about PAH see: NHLBI www.nhlbi.nih.gov/health/health-topics/topics/pah/); Pulmonary Hypertension Association www.phassociation.org; and the American Lung Association www.lungusa.org.

This article was published in the Winter 2007 issue of the ALA Lung Health Magazine.