Many doctors give the clot-dissolver hoping it will make the artery-widening operation more successful. But research presented Tuesday at the annual conference of the European Society of Cardiology found that more patients died in the month after the procedure if they were given the drug.

Experts said the findings are expected to prompt many doctors to stop using the strategy, at least for now.

"A great clinical trial is one that provides a clear-cut answer to the question that is being asked, is one that raises new questions and is one that influences the practice of medicine. [This study] certainly meets all these three criteria," said Dr. William Wijns, a leader in the field of angioplasty who was not connected with the research.

Two Main Options

There are two main options for treating heart attack victims: a clot dissolving drug or angioplasty, where doctors thread a wire through the blood vessels to reach the blood clot that caused the heart attack.

The wire breaks up the clot. Doctors then inflate a balloon to squash plaque against the wall of the artery and implant a tiny mesh tube at the site of a blockage to permanently prop the artery open.

Angioplasty is considered the more effective option as long as it is done by experienced doctors in well-equipped hospitals. However, most community hospitals do not have such expertise. In those places, patients are either treated with a clot-busting drug or transferred to a nearby hospital that can perform the angioplasty within three hours.

Difference in Death Rates

However, it has been unclear whether angioplasty would work better if the clot was dissolved before the procedure in cases where angioplasty cannot be performed immediately but can be done within three hours. Some doctors have been giving the clot-buster to patients in this situation anyway, hoping it will help.

In the latest study, led by Dr. Frans Van de Werf of the Catholic University of Leuven in Belgium, the strategies were compared in 1,667 patients in hospitals. Half were given the clot-buster while en route to angioplasty, while the other half were given a fake pill.

The researchers found that 6 percent of patients who got the drug, TNKase, died within 30 days of the angioplasty, compared with only 3.8 percent of those in the angioplasty alone group.

The study, which was supposed to enroll 4,000 patients, was stopped prematurely once the difference in death rates between the two groups became apparent.

Wijns, co-director of the Cardiovascular Center at the Onze-Lieve-Vrouw Hospital in Aalst, Belgium, said the findings were an important contribution. However, he said they may not be the last word. Other studies testing different combinations of drugs surrounding angioplasty are eagerly awaited, he said.