Role of anticoagulant therapy in atrial fibrillation.

Atrial fibrillation belongs to the group of cardiovascular diseases that most frequently predispose to arterial thromboembolic events. Within the last years, the AFASAK, BAATAF, SPAF I, SPINAF, and CAFA trials have consistently demonstrated a significant, approximately 70%, risk reduction for stroke on oral anticoagulation in patients with nonrheumatic atrial fibrillation. This benefit by far outweighed the slight increase in annual major hemorrhage. Recently, additional trials (SPAF II, EAFT, SPAF III, and others) have shed further light on important questions concerning risk factors, secondary prophylaxis, the optimal intensity of anticoagulation, and the role of aspirin and other antiplatelet drugs. The main results of these studies are discussed in this review. The majority of patients with atrial fibrillation are > 65 years of age and have other clinical or echocardiographic risk factors. In these patients, adjusted-dose warfarin with target international normalized ratios (INRs) 2.0 to 3.0 is effective and safe. The risk of stroke rises with INR values < 2.0, whereas INR values > 3.0 result in an increase in intracerebral hemorrhages, especially in the very elderly. In contrast, no anticoagulation seems warranted in younger atrial fibrillation patients < 60 years of age without any clinical or echocardiographic risk factor. An overview of all randomized trials that compared aspirin with placebo and/or adjusted-dose warfarin indicates that adjusted-dose warfarin is approximately 50% more effective than aspirin for primary and secondary prevention of stroke, at least in patients with atrial fibrillation who have clinical risk factors. Therefore, oral anticoagulation clearly is the therapy of choice for prevention of thromboembolism in patients with atrial fibrillation.