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HEALTH : Heart Drugs Do Equally Well in Study

Times Medical Writer

One of the most consuming questions in heart-attack treatment--which of two revolutionary clot-dissolving drugs is preferable--has received a surprising partial answer from one of the first studies to compare the two therapies.

The study, published Thursday in the New England Journal of Medicine, found that the two competing drugs--one priced at $2,200 per treatment, the other costing one-tenth as much--are equally effective in preserving the pumping power of the heart.

That unexpected conclusion emerged from an examination of 270 patients treated with one or the other of the drugs--a much ballyhooed biotechnology product known as TPA and an ordinary enzyme called streptokinase extracted from bacteria.

“It’s very intriguing and it’s an excellent study,” said Dr. Eric Topol, a University of Michigan associate professor who has done research on TPA. “It’s going to heat up the controversy one more notch.”

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The two drugs, approved by the Food and Drug Administration in 1987 for intravenous use, have helped revolutionize the treatment of heart attack, which strikes 1.5 million Americans annually when one or more of their coronary arteries become blocked.

In the past, physicians were largely unable to intervene to stop a heart attack while it was occurring. Instead, they attempted to reduce the patient’s chest pain and avert other problems that might be prompted by the attack.

The new drugs actually dissolve the clots that lodge in narrowed arteries, cutting off blood flow to the heart. Studies suggest that these and other clot-dissolving drugs could reduce heart-attack deaths by as much as 50% if used within hours of initial symptoms.

Researchers disagree, however, on which drug is preferable. TPA appears to clear arteries more quickly, but is much more expensive. There have been few attempts to directly compare TPA and streptokinase.

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Cost Is Focus of Study

The debate over the drugs’ relative merits, and concern about the rising costs of medicine, prompted federal health-care financing officials last year to decline for the time being to reimburse hospitals at a higher rate for TPA treatment of Medicare patients.

“It’s the new biology versus the old, the expensive versus the inexpensive,” Topol said of the debate.

About 25% of all heart-attack patients are eligible for clot-dissolving therapy, currently recommended for use in patients under 75 and within four to six hours of the onset of symptoms. Researchers believe that percentage would rise with improved public awareness of symptoms.

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The percentage of heart-attack patients actually receiving the therapy is believed to be much lower, however, because many small hospitals lack the facilities to administer the treatment and because some general practitioners are unwilling to use it.

In the study, by researchers in New Zealand, half the 270 patients received streptokinase, an enzyme extracted from streptococcus bacteria. The other half received TPA, a genetically engineered replica of a protein produced naturally in the body.

All of the patients were having their first heart attack.

The two drugs had similar effects on the heart’s pumping capacity, measured by the percentage of blood ejected on each heartbeat. When measured three weeks after treatment, that percentage was 58% in both groups. The norm in healthy hearts is 71%, the researchers said.

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Reopening Arteries

The drugs also were equally effective in reopening clogged arteries, which is important in minimizing damage to the heart muscle and the organ’s ability to pump. Although 10 patients on streptokinase died within 30 days, compared to five on TPA, the researchers said the gap was not statistically significant because the numbers were so small.

The New Zealand study did not attempt to compare the drugs’ effects on long-term survival, considered the most important measure of a clot-dissolver’s effectiveness. Pumping power, however, is considered a powerful predictor of survival, the researchers said.

A larger study, comparing the two drugs in thousands of patients in Western Europe, is expected to produce preliminary results in 1990. An even more extensive trial examining the two drugs and a third called APSAC is also in the works.

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