DALLAS (American Heart Association) -- People who survive more than one heart attack or stroke caused by a blood clot have a lower risk of having another event if they are treated with the blood-thinning drug clopidogrel instead of aspirin, according to a report in the rapid access issue of Stroke: Journal of the American Heart Association.

Researchers studied participants in the CAPRIE (Clopidogrel Versus Aspirin in Patients at Risk of Ischemic Events) trial who had a history of heart attack or stroke. In CAPRIE, physicians had randomized patients to receive either clopidogrel or aspirin after a cardiovascular event (CVE).

In the overall CAPRIE study, clopidogrel-treated participants had an 8.7 percent lower relative risk compared to the aspirin-takers. In this study of high-risk patients reported in the journal today, the clopidogrel group had a 14.9 percent lower relative risk.

Researchers followed 4,496 patients after suffering a second cardiovascular event. They discovered that after one- and three-year follow-ups, the clopidogrel patients were less likely than those taking aspirin to have been hospitalized for or to have died from a CVE.

"Basically, if a patient has a history of multiple cardiovascular events, they are better off being treated with clopidogrel rather than aspirin," said co-author Deepak L. Bhatt, M.D., director of the Interventional Cardiology Fellowship at the Cleveland Clinic Foundation in Ohio.

The study confirmed that people who suffer a second CVE have a high risk of experiencing a third, Bhatt said. "Unfortunately the third event may be fatal."

He said it is also important for physicians and patients to realize that a second or third event may not be the same as the first.

"Just because a patient came in with a heart attack today doesn't mean he or she is only at risk for a future heart attack," Bhatt said. "The next time, it may be a stroke or other arterial problem." The same mechanism -- a lack of oxygen caused by blockages that narrow the arteries -- underlies heart attacks, strokes, and vascular problems elsewhere in the body such as in the leg arteries, he said.

The study found that one year after their second event, 16.1 percent of the clopidogrel group and 18.5 percent of the aspirin group had suffered a stroke or heart attack, or been hospitalized again for a CVE. After three years, 32.7 percent for those on clopidogrel and 36.6 percent of those taking aspirin had another CVE. These findings emphasize how often patients with a previous heart attack or stroke are re-hospitalized, Bhatt said.

Researchers also found that 8.8 percent of the clopidogrel-treated patients had a stroke, heart attack or died versus 10.2 percent of those taking aspirin at the one-year follow-up. After three years, 20.4 percent of patients in the clopidogrel group and 23.8 percent of those on aspirin had died from a CVE.

Statistically, the findings indicate that treating 29 of these very high-risk patients with clopidogrel would prevent one death, heart attack or stroke over three years. The study results also indicate that the benefits of clopidogrel over aspirin are amplified in people who have suffered previous CVEs.