Primary endpoint (stroke, systemic embolus, myocardial infarction and vascular death in the ACTIVE W Study comparing oral anticoagulation with warfarin against a fixed dose of clopidogrel and aspirin (A). The occurrence of major bleeding (B). ASA, aspirin; OAC, oral anticoagulation. Modified with permission from Connolly S, Pogue J, Hart R, et al.; ACTIVE Writing Group on behalf of the ACTIVE Investigators. Clopidogrel plus aspirin versus oral anticoagulation for atrial fibrillation in the Atrial fibrillation Clopidogrel Trial with Irbesartan for prevention of Vascular Events (ACTIVE W): a randomised controlled trial. Lancet 2006; 367: 1903–12.