James Kiley, Ph.D., Elizabeth Denholm, Ph.D.
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.