Ximelagatran vs Warfarin for Stroke Prevention in Patients With Nonvalvular Atrial Fibrillation

CONTEXT: In patients with nonvalvular atrial fibrillation, warfarin prevents ischemic stroke, but dose adjustment, coagulation monitoring, and bleeding limit its use. OBJECTIVE: To compare the efficacy of the oral direct thrombin inhibitor ximelagatran with warfarin for prevention of stroke and systemic embolism. DESIGN, SETTING, AND PARTICIPANTS: Double-blind, randomized, multicenter trial (2000-2001) conducted at 409 North American sites, involving 3922 patients with nonvalvular atrial fibrillation and additional stroke risk factors. INTERVENTIONS: Adjusted-dose warfarin (aiming for an international normalized ratio INR 2.0 to 3.0) or fixed-dose oral ximelagatran, 36 mg twice daily. MAIN OUTCOME MEASURES: The primary end point was all strokes (ischemic or hemorrhagic) and systemic embolic events. The primary analysis was based on demonstrating noninferiority within an absolute margin of 2.0% per year according to the intention-to-treat model. RESULTS: During 6405 patient-years (mean 20 months) of follow-up, 88 patients experienced primary events. The mean (SD) INR with warfarin (2.4 0.8) was within target during 68% of the treatment period. The primary event rate with ximelagatran was 1.6% per year and with warfarin was 1.2% per year (absolute difference, 0.45% per year; 95% confidence interval, -0.13% to 1.03% per year; P<.001 for the predefined noninferiority hypothesis). When all-cause mortality was included in addition to stroke and systemic embolic events, the rate difference was 0.10% per year (95% confidence interval, -0.97% to 1.2% per year; P = .86). There was no difference between treatment groups in rates of major bleeding, but total bleeding (major and minor) was lower with ximelagatran (37% vs 47% per year; 95% confidence interval for the difference, -14% to -6.0% per year; P<.001). Serum alanine aminotransferase levels rose to greater than 3 times the upper limit of normal in 6.0% of patients treated with ximelagatran, usually within 6 months and typically declined whether or not treatment continued; however, one case of documented fatal liver disease and one other suggestive case occurred. CONCLUSIONS: The results establish the efficacy of fixed-dose oral ximelagatran without coagulation monitoring compared with well-controlled warfarin for prevention of thromboembolism in patients with atrial fibrillation requiring chronic anticoagulant therapy, but the potential for hepatotoxicity requires further investigation.