Warfarin, aspirin, or both after myocardial infarction.

Background: The role of antithrombotic therapy in secondary prevention after myocardial infarction is well established. Although the available literature suggests that warfarin is superior to aspirin, aspirin is currently the more widely used drug. We studied the efficacy and safety of warfarin, aspirin, or both after myocardial infarction. Methods: In a randomized, multicenter trial in 3630 patients, 1216 received warfarin (in a dose intended to achieve an international normalized ratio [INR] of 2.8 to 4.2), 1206 received aspirin (160 mg daily), and 1208 received aspirin (75 mg daily) combined with warfarin (in a dose intended to achieve an INR of 2.0 to 2.5). The mean duration of observation was four years. Results: The primary outcome, a composite of death, nonfatal reinfarction, or thromboembolic cerebral stroke, occurred in 241 of 1206 patients receiving aspirin (20.0 percent), 203 of 1216 receiving warfarin (16.7 percent; rate ratio as compared with aspirin, 0.81; 95 percent confidence interval, 0.69 to 0.95; P=0.03), and 181 of 1208 receiving warfarin and aspirin (15.0 percent; rate ratio as compared with aspirin, 0.71; 95 percent confidence interval, 0.60 to 0.83; P=0.001). The difference between the two groups receiving warfarin was not statistically significant. Episodes of major, nonfatal bleeding were observed in 0.62 percent of patients per treatment-year in both groups receiving warfarin and in 0.17 percent of patients receiving aspirin (P<0.001). Conclusions: Warfarin, in combination with aspirin or given alone, was superior to aspirin alone in reducing the incidence of composite events after an acute myocardial infarction but was associated with a higher risk of bleeding.