The ExTRACT-TIMI 25 Trial shows that use of enoxaparin after an acute myocardial infarction reduces risk for repeat infarction or death compared with unfractionated heparin, according to a presentation at the annual meeting of the American College of Cardiology.

The ExTRACT-TIMI 25 (Enoxaparin and Thrombosis Reperfusion for Acute Myocardial Infarction Treatment - Thrombolysis in Myocardial Infarction) trial was a randomized, double-blind, double-dummy comparison of two anticoagulant strategies in more than 20,000 patients in 48 countries whose primary treatment for myocardial infarction was fibrinolytic therapy. A new strategy using enoxaparin was used for the duration of hospitalization and was compared with the current strategy, unfractionated heparin for at least 48 hours.

The results showed that the risk of death or recurrent non-fatal myocardial infarction was significantly reduced by 17 percent for patients who received enoxaparin compared with those who received unfractionated heparin. The benefits of enoxaparin became apparent within 48 hours. At the end of one month, the risk of recurrent non-fatal infarction was significantly reduced by 33 percent for patients given enoxaparin compared with unfractionated heparin. A total of 7.5 percent of patients who received unfractionated heparin died compared with 6.9 percent who received enoxaparin.

Elliott Antman, MD, Director, Samuel A. Levine Cardiac Unit at Brigham and Women's Hospital, Professor of Medicine, Harvard Medical School, and lead author of the ExTRACT-TIMI 25 study said, "The results of this trial are dramatic and significant; a strategy using enoxaparin prevents more patients from dying or having a second heart attack within 30 days of treatment compared to the strategy using unfractionated heparin, which up to now has been considered the standard blood thinner regimen used to support fibrinolytic therapy."

"Enoxaparin, a modified form of unfractionated heparin, interrupts the clotting system more efficiently and more reliably than unfractionated heparin. By doing so, enoxaparin prevents blood clots from forming again in arteries that carry blood to the heart muscle."

The rates of serious bleeding overall were lower than reported in previous trials. The patients who received enoxaparin compared with unfractionated heparin strategy did have a small but significant increase in the risk of serious bleeding. However, when the balance of benefits and risks were weighed ("net clinical benefit"), the results strongly favored the enoxaparin.

The study has critical importance for the treatment of most patients hospitalized for an acute myocardial infarction, said Antman. "Although opening a blocked coronary artery with a balloon-tipped catheter, or percutaneous coronary intervention, has been shown to be an effective treatment for heart attack patients who come to specialized centers, the vast majority of patients worldwide receive clot-busting medications to treat their heart attack."

"Based on the results of the ExTRACT-TIMI 25 trial, we believe that the enoxaparin strategy is now the preferred anticoagulant regimen to use in heart attack patients who receive clot-busting drugs," said Eugene Braunwald, M.D., M.A.C.C., Chairman, TIMI Study Group, Brigham and Women's Hospital and Distinguished Hersey Professor of Medicine, Harvard Medical School.