The most common cause of pulmonary hypertension (PH) is a common illness itself: chronic obstructive pulmonary disease, or COPD. But severe pulmonary hypertension is a rarity in people with COPD, considered the fourth leading cause of death in the United States.¹

That's the conclusion of a group of doctors who, in a study, looked at the prevalence of severe PH in a large group of patients. Their conclusions are published in the July 15 issue of the American Journal of Respiratory and Critical Care Medicine.²

"Severe pulmonary hypertension is uncommon in patients with COPD," wrote Ari Chaouat, MD, a respiratory specialist at Hopital de Hautepierre in Strasbourg, France, and his fellow researchers. "When it occurs, another cause must be sought."

Incessant Hypertension
Pulmonary arterial hypertension is a condition characterized by continual high blood pressure in the pulmonary artery, which carries blood low in oxygen from the heart to the lungs so that it can be re-oxygenated. The average blood pressure in the pulmonary artery in a healthy individual is around 14 mm Hg; however, in PH patients, the pressure rises to more than 25 mm Hg.

When PH strikes, the muscles inside the walls of the arteries may tighten up, causing the arteries to narrow; the walls of the pulmonary arteries may thicken as the amount of muscle rises in them and resulting scar tissue forms; and tiny blood clots may form within these narrower arteries, causing potential blockages.

There are two types of pulmonary hypertension:

• Primary—the disease develops with no known underlying cause.
• Secondary—the disease is caused by, or occurs because of, another condition. These underlying conditions include blood clots in the lung, and diseases like scleroderma or COPD.³

Approximately 300 new cases of primary pulmonary arterial hypertension are diagnosed in the United States annually. Secondary PH is more common.³

Treatment does not cure PH, but only helps people with the disease manage their symptoms. Those include anticoagulants; calcium channel blockers, which relax and open blood vessels; epoprostenol (Flolan/a prostacyclin), which widens the arteries of the lung and inhibits blood clotting; treprostinil (Remodulin), another prostacyclin; bosentan (Tracleer); inhaled nitric oxide; sildenafil (Viagra); and diuretics, which may help ease symptoms and help the heart perform better.⁴

Questions About the Co-Existing Illnesses
As severe PH occurs occasionally in people with chronic obstructive pulmonary disease, Chaouat and his team wanted to derive more knowledge about these co-existing ailments. Up to this point, "no detailed description of these patients" had been available, they wrote.

To clarify how often severe PH occurs in people with COPD, Chaouat and his team conducted a retrospective study of 27 patients with both illnesses. They were among nearly 1000 patients who had undergone a heart catheterization procedure, designed to open narrowed arteries, between 1990 and 2002 "as part of a workup for chronic respiratory failure during a period of disease stability." The researchers pulled records on all 27 patients, and examined the relevant data. The average pulmonary artery pressure for these patients with both COPD and PH was at least 40 mm Hg.

PH Wasn't Common
Of these patients, 16 had a second disease that could have caused their severe pulmonary hypertension. "The remaining eleven patients had COPD as the only cause of pulmonary hypertension," Chaouat and his colleagues reported.

Compared with a second group of patients whose records were analyzed, and who had COPD without PH, the eleven patients with both diseases had an unusual pattern of cardiopulmonary abnormalities with mild to moderate breathing difficulties, severely low blood levels of both oxygen and carbon dioxide (hypoxemia, hypocapnia), and a very low ability to diffuse carbon monoxide.

The patients with both illnesses also had extreme shortness-of-breath, and their odds of survival were shorter compared to the patients with COPD alone, or other pulmonary hypertension patients.

In conclusion, the French researchers determined that severe PH is a rarity in COPD, and that when it does occur, another cause should be sought. "COPD with severe pulmonary hypertension and no other possible cause shares features with pulmonary vascular disease, such as idiopathic pulmonary hypertension," they wrote.

1. National Heart, Lung, and Blood Institute. National Institutes of Health (NIH). Chronic Obstructive Pulmonary Disease. Available at: http://www.nhlbi.nih.gov/health/public/lung/other/copd_fact.pdf. Accessed September 15, 2005.
2. Chaouat A, Bugnet AS, Kadaoui N et al. Severe pulmonary hypertension and chronic obstructive pulmonary disease. Am J Respir Crit Care Med 2005 Jul 15;172(2):189-94. Epub 2005 Apr 14.
3. National Heart, Lung and Blood Institute. National Institutes of Health (NIH). What is Pulmonary Arterial Hypertension? Available at: http://www.nhlbi.nih.gov/health/dci/Diseases/pah/pah_what.html. Accessed September 15, 2005.
4. National Heart, Lung and Blood Institute. National Institutes of Health (NIH). How is Pulmonary Arterial Hypertension Treated? Available at: http://www.nhlbi.nih.gov/health/dci/Diseases/pah/pah_treatments.html. Accessed September 15, 2005.