Objective: To review the evidence for antithrombotic therapy in patients with nonrheumatic atrial fibrillation.
Quality of evidence: Five primary prevention trials and one secondary prevention trial compare antithrombotic therapy with placebo or no treatment. Two trials also determine the efficacy and safety of acetylsalicylic acid.
Main findings: Warfarin reduces the risk of stroke by 68%. The effect is consistent in all identifiable groups of patients with nonrheumatic atrial fibrillation, except patients at serious risk of hemorrhage. The absolute benefit of anticoagulants varies among patients because of markedly different inherent risk of stroke among patient subgroups.
Conclusions: Anticoagulant therapy should be considered for all patients with atrial fibrillation. Oral anticoagulant therapy is more effective than ASA in reducing the risk of stroke among patients with nonrheumatic atrial fibrillation.