Anticoagulation and atrial fibrillation. Putting the results of clinical trials into practice.

The thromboembolic risk of atrial fibrillation varies with the underlying cause, associated heart disease, and history of previous embolism. Decisions regarding warfarin anticoagulation therapy require a careful assessment of relative risks of thromboembolism and bleeding. Anticoagulation is strongly indicated for valvular atrial fibrillation and to prevent recurrent stroke in patients with atrial fibrillation and previous stroke or transient ischemic attack. Several randomized trials have consistently shown a reduction of the risk with the use of warfarin in nonvalvular atrial fibrillation, and anticoagulation is recommended. With a careful selection of patients, the risk of major bleeding on warfarin therapy is 2% to 4% per year. Aspirin therapy is less efficacious but also less risky than warfarin. Patients younger than 60 with lone atrial fibrillation do not require anticoagulation.