Rationale for antithrombotic therapy in atrial fibrillation.

Antithrombotic therapy is clearly indicated in patients with atrial fibrillation who have associated factors that put them at significant risk for thromboembolism This does not include subjects with lone atrial fibrillation who are less than 60 years of age. High-risk patients include those with valvular heart disease, recent congestive heart failure, severe left ventricular dysfunction by echocardiography, prior thromboembolism, demonstration of a cardiac thrombus by echocardiography, and thyrotoxicosis. Anticoagulant therapy appears to be the most efficacious means of preventing thromboembolism in atrial fibrillation. Potential bleeding complications with sodium warfarin mandate judicious selection of patients for long-term anticoagulant therapy. The risk of anticoagulant therapy certainly appears justified in subjects who are at high risk for thromboembolism and can be monitored with a reasonable degree of safety. Aspirin therapy is a reasonable alternative for those subjects at relatively lower risk of thromboembolism, especially subjects who are not suitable candidates for anticoagulation. The efficacy of aspirin has not been established in patients with atrial fibrillation who are greater than 75 years of age.