"The chance of artery closure was reduced by 45 percent by the combined therapy," says researcher Freek W.A. Verheugt, M.D., Ph.D. "This study shows that patients should use at least three months of oral anticoagulants plus aspirin after they have been treated with clot busters for a heart attack."

Survival after a myocardial infarction marked by ST-segment elevation depends on how quickly coronary blood flow is restored. Recurrent infarctions are often attributed to reocclusion of the artery involved in the original infarction. Arteries reocclude after successful use of fibrinolytics in as many as 30 percent of patients within the first year, Verheugt says.

"In Europe, it is common to add oral anticoagulants to aspirin treatment in patients with clogged coronary arteries," he says.

Researchers hypothesized that prolonged use of aspirin and coumarin would be more effective than the standard treatment of aspirin alone. They identified 308 patients with myocardial infarction who were participating in the Antithrombotics in the Prevention of Reocclusion in Coronary Thrombolysis (APRICOT)-2 study in The Netherlands between 1994 and 2000.

Within 48 hours of thrombolytic therapy, doctors tested patients' blood flow on the Thrombolysis in Myocardial Infarction (TIMI) scale, a measure of flow through the affected artery. Patients with a TIMI flow grade of three (signaling patent arteries) were eligible to participate. Participants ranged in age from their mid-40s to early 60s, and just over 80 percent were male.

A group of 123 patients took aspirin and a moderate dose of coumarin. Because they continued to take heparin until moderate anticoagulation was achieved, as many as 66 additional hours of heparin treatment were required. In contrast, a group of 128 control patients used only the daily dose of aspirin and had no additional heparin.

Researchers performed follow-up angiography after three months. Reocclusion occurred in 15 percent of the combined group and in 28 percent of the aspirin-only group (19 patients and 36 patients, respectively). Problem-free survival was also significantly higher in the combined group - 86 percent vs. 66 percent--- and these patients had a significantly lower incidence of a second myocardial infarction - 2 percent versus 8 percent.