Heart attacks and deaths nearly doubled after patients stopped taking the anti-clotting drug Plavix, according to the first national study documenting the risk to heart patients who stop drug therapy.

The study of more than 3,000 U.S. military veterans who had heart attacks or chest pain found that risk of another heart attack or death spiked in the 90 days after they stopped taking the medication, made by Bristol-Myers Squibb Co. and Sanofi-Aventis SA. The study, funded by the U.S. Department of Veterans Affairs, appears in today's Journal of the American Medical Association.

The findings, if confirmed, could alter care for heart attack patients treated with drugs or drug-coated stents that prop open clogged arteries, said lead researcher John Rumsfeld, a cardiologist at the Denver VA Medical Center.

About 775,000 people have mild heart attacks or chest pain known as acute coronary syndrome in the U.S. each year. One treatment involves drug-coated stents from Boston Scientific Corp. in Maple Grove or from Johnson & Johnson to prop open the artery. Worries about blood clots related to drug-coated stents caused U.S. sales to plunge 30 percent last year to about $2 billion.

Another heart treatment is Plavix and other drugs, which a study last year said was as effective as stents in preventing future heart attacks and death.

Heart patients take Plavix, also known as clopidogrel, daily for up to a year to prevent new clots. They should talk to their doctors after finishing treatment to decide whether to continue taking Plavix, Rumsfeld said.

The researchers examined data on 3,137 veterans treated from October 2003 to March 2005 at 127 VA hospitals. More than 60 percent of the 268 second heart attacks and deaths among those given drugs occurred within 90 days of stopping Plavix, as did 59 percent of the 124 deaths among patients treated with stents and taking Plavix.

But patients on Plavix can develop serious bleeding, Rumsfield said. Also, the drug costs $3 to $5 a pill.

Boston Scientific has an education program encouraging people to take their Plavix, said Jeff Mirviss, vice president of stent marketing. The company is funding studies to learn why clots form around stents and is developing new stents designed to minimize the risk, he said.

Star Tribune staff writer Janet Moore contributed to this report.