New research indicates that up to 50 percent of Asians carry a genetic variant or “polymorphism” that makes nitroglycerin less effective, or even ineffective, for the treatment of angina.

Angina is a pain in the chest that occurs when blood flow, and thus oxygen flow, to the heart is insufficient. It is the top symptom of coronary artery disease.

Stable angina occurs during exertion and can usually be treated with rest and nitroglycerin, which is placed under the tongue. Unstable angina generally occurs when a person is at rest. It is much more serious than stable angina and often signals an impending heart attack.

Findings from a recent study showed that for nitroglycerin to work, a functioning enzyme, known as ALDH2, is required. The enzyme is responsible for forming nitric oxide, the metabolite of nitroglycerin.

In The Journal of Clinical Investigation, Dr. Li Jin, from Fudan University in Shanghai, China and associates present evidence to suggest that the reason many Asians have a suboptimal response to nitroglycerin is because they harbor a gene variant - Glu504Lys - that makes ALDH2 virtually inactive.

The study involved 111 Chinese patients taking nitroglycerin for heart disease, of whom 31 did not respond to the drug.

The investigators think that this genetic factor needs to be considered when nitroglycerin is given to patients, especially Asian patients.

SOURCE: Journal of Clinical Investigation, online January 26, 2006.