MEDICINE USED TO TREAT CHEST PAIN TOUTED AS REDUCING FATAL ATTACKS.

Byline: Associated Press

A powerful new clot-preventing medicine appears to cut the risk of heart attack and death almost in half in people hospitalized with severe chest pain, a medical emergency that afflicts more than 1 million Americans annually.

The drug is one of a new class of medicines that are likely to revolutionize the treatment of unstable angina, an ominous attack of chest pain that is the leading reason for admitting people to coronary care units.

The medicine is a sort of super aspirin that works by stopping the formation of blood clots. These clots can trigger heart attacks by choking off the supply of blood to the heart muscle.

Currently, aspirin and a blood thinner called heparin are the mainstays of treatment for unstable angina. The new medicine proved to be powerfully effective when used in addition to these.

Doctors say the new therapy may turn out to be even more important than clot-dissolving drugs, an entirely different group of medicines that have transformed the treatment of heart attacks over the past decade.

``These are landmark studies that represent a scientific breakthrough,'' said Dr. Harvey D. White of Green Lane Hospital in Auckland, New Zealand.

White said the drug will save the lives of 13 of every 1,000 unstable angina patients treated. By comparison, TPA, the leading clot-dissolver, saves 10 of every 1,000 heart attack patients treated.

White directed one of two large studies on the drug, called Aggrastat, that were released Monday at a meeting of the American College of Cardiology.

Dr. Rick Sax, who developed the drug at Merck & Co., estimated that if all the 1.2 million unstable angina patients hospitalized in the United States each year received Aggrastat, it would prevent between 5,000 and 10,000 deaths and 30,000 to 40,000 heart attacks.

Aggrastat is considered experimental. Merck plans to ask the Food and Drug Administration later this year for permission to put it on the market.

Typically, unstable angina occurs when a fatty buildup on an artery wall breaks open during some form of stress. Blood cells called platelets congregate in this wound and clump together. In the narrow confines of an artery, this clot can be disastrous, for it may block blood flow entirely.

The platelets are hooked together by a protein called fibrinogen, which latches onto spots on the cells called glycoprotein IIb-IIIa receptors. Aggrastat - or tirofiban - is one of a class of medicines called glycoprotein IIb-IIIa blockers. As the name implies, the medicine keeps fibrinogen from linking up platelets to form clots.

Actually, 90 different biochemical triggers can start the cascade of steps that lead to clots. Aspirin blocks one of these steps. Aggrastat blocks all of them.