A provocative new study challenges the notion that heart attack victims have only 12 hours in which to undergo an artery-clearing angioplasty. The study found that patients who had the procedure as much as two days after being stricken still benefited.

Although the study was too small to be conclusive, the findings "are a noteworthy challenge to existing dogma and an important contribution to current knowledge," Drs. Raymond Gibbons of the Mayo Clinic and Cindy Grines of William Beaumont Hospital in Detroit said in an accompanying editorial.

Cardiologists generally believe they have a 12-hour window after a heart attack starts to reopen clogged arteries and save heart muscle from damage caused by interrupted blood flow. Current guidelines discourage angioplasties beyond that window.

But in the study of 365 European patients hospitalized between 12 and 48 hours after symptoms began, patients who got immediate angioplasties had substantially less heart-muscle damage than those treated initially with drugs alone.

Tests several days after treatment showed that 8 percent of the heart muscle was damaged in angioplasty patients versus 13 percent in the others.

Less heart muscle damage usually means better outcomes, and there were fewer deaths, recurrent heart attacks and strokes among the angioplasty patients within 30 days of treatment. But the study was too small to determine whether that was due to anything more than chance.

The study was published in Wednesday's Journal of the American Medical Association and led by Dr. Albert Schomig of Technische University in Munich, Germany.

Up to about 40 percent of heart attack patients seek treatment beyond the 12-hour window, the researchers said. In the United States alone, that is more than 300,000 of the nearly 900,000 people who will have heart attacks this year.

In an angioplasty, a catheter with a balloon tip is threaded into an artery to clear away a blockage. Tiny mesh cylinders called stents often are then inserted to keep the cleared artery propped open.

The study involved patients treated in Germany, Austria and Italy. All received the anti-clotting drugs Plavix or ticlopidine, plus aspirin and the blood-thinner heparin.

About half also got immediate invasive treatment — mostly angioplasty with stents. This group also got a newer drug called ReoPro that helps prevent clots that can cause a heart attack.

There were eight deaths, recurrent heart attacks or strokes in the angioplasty group versus 12 in the others.

The study was partly funded by the makers of ReoPro and heart stents.

Cleveland Clinic cardiologist Dr. Steven Nissen said the angioplasty group's use of ReoPro might explain the differing results.

Dr. Sidney Smith, an American Heart Association spokesman, said an unusually large number of patients in the study had relatively little tissue damage and continued blood flow to the damaged area before treatment, so the results might not apply to a broader population.