A chemical that dissolves blood clots offers new hope of cutting the death rate from heart attacks.

In most hea w0104 ----- r a BC-06/02/83-HEART 06-02 0001 Enzyme May Cut Heart Attack Damage By Victor Cohn Washington Post Staff Writer

A chemical that dissolves blood clots offers new hope of cutting the death rate from heart attacks.

In most heart attacks, it is a blood clot that blocks the heart's major blood vessels and quickly leads to death of heart muscle. Two reports in today's New England Journal of Medicine offer strong evidence for what the journal calls "a new potential" for preventing much of this damage.

The key is speedy treatment with a powerful enzyme--a product of streptococcus bacteria--called streptokinase.

According to Dr. H.J.C. Swan, cardiology chief at Los Angeles' Cedars-Sinai Medical Center and author of an editorial summing up the reports, they indicate that when heart patients reach a hospital within three to four hours, heart muscle can often be saved by use of the enzyme.

Large numbers of heart attack victims are reaching the hospital quickly today. With modern rescue squads, "30 to 50 percent of patients can reach a hospital within three hours, so there is considerable potential now for thrombolysis," chemical destruction of clots, Swan said in an interview.

He cautioned that "all the answers aren't in . . . . We still have to learn what the best thrombolytic agent might be" (others are also being tested) and that in the meantime doctors should use strep- tokinase "with great care and caution."

Streptokinase is regularly used to dissolve pulmonary embolisms, clots in the large pulmonary artery that carries blood from the heart to the lungs. And the enzyme is being used by some doctors for heart attack patients. Results in the latter case have been mixed, said Swan, probably due to poor timing in administering the enzyme to the patients.

It is the new studies, he said--"the first randomized, controlled trials reported in this country"--that sharply demonstrate the need for rapid use of streptokinase.

Dr. Fareed Khaja and 12 associates at Detroit's Henry Ford Hospital and the University of Michigan gave 40 patients either a harmless and ineffectual sugar solution or streptokinase, injecting the enzyme directly into the coronary arteries.

They reestablished blood flow in these crucial heart vessels in 12 of 20 patients treated with streptokinase. One streptokinase patient died in the hospital, compared with four in the "control group" given the sugar solution.

The streptokinase failed to improve permanent heart function in these Michigan patients. But the doctors started giving them the enzyme an average of 5.4 hours after the first chest pains.

In contrast, Dr. Jeffrey Anderson and eight colleagues at the University of Utah and LDS Hospital in Salt Lake City gave 24 patients streptokinase an average of four hours after their heart attacks started.

Compared with 26 patients given standard coronary care unit treatment, the 24 showed "a clear-cut and significant benefit," in Swan's words, as measured by several tests. These included electrocardiogram results and tests of heart function. Only one streptokinase patient died in the hospital, compared with four in the conventional group.

"We need more studies," Swan said. But "there is now the hope of a major advance" in heart treatment, comparable to the advances wrought in the last few years by beta-blockers and other drugs that help stricken hearts to function.