A new clot-preventing drug called bivalirudin is much more effective than existing drugs at stopping clot formation during balloon angioplasty for severe heart attacks, reducing the risk of death by a third, researchers reported.

The results “provide an advance over what the standard for treatment was,” a cardiologist at the University of California, Los Angeles’ Geffen School of Medicine who was not involved in the research, Dr. Gregg Fonarow, said. “Many large centers have begun using it already and, with the publication of this trial, we’ll see even greater use.”

In a second study, researchers found that combining angioplasty with a different drug that dissolves, rather than prevents clots provided no benefit for survival and doubled the risk of major bleeding episodes.

“It is time to abandon the routine use of” the method until researchers can find a better and safer way to perform it, Dr. Jane A. Leopold of Brigham and Women’s Hospital in Boston, who was not involved in the research, said.

The two studies together are likely to subtly change the way emergency physicians treat major heart attacks, improving the safety of the procedures and increasing the likelihood of survival.

Both of the reports, published in The New England Journal of Medicine, dealt with the most severe form of heart attacks in which a clot almost totally blocks one of the arteries supplying blood to the heart. Such severe episodes account for about 30% of the estimated 1 million heart attacks that strike Americans each year.

Angioplasty, which involves physically compressing the clot with a balloon threaded through the artery, is now the preferred method for opening arteries because it has a significantly higher success rate.

To minimize formation of new clots during and after angioplasty, surgeons typically use a combination of blood-thinning drugs and a clot-preventing agents.