[Atrial fibrillation and apoplexy--risks and prevention]

The annual incidence of ischemic stroke among patients with chronic non-valvular atrial fibrillation is about 4.5 percent. In five controlled trials, oral anticoagulant therapy with warfarin reduced the annual incidence of stroke by 68 percent to 1.4 percent. The effect of aspirin has not been unequivocally determined. Aspirin reduced the annual risk of stroke by 18 percent (n.s.) in one trial, and by 44 percent in another, though the two trials differed both in mean age of the patients and in aspirin doses. Direct comparison of warfarin and aspirin revealed no difference in efficacy. Advanced age, previous stroke or transient ischemic attack (TIA), hypertension and diabetes were all found to be risk factors for stroke in patients with atrial fibrillation. In patients under 65 years of age without risk factors, the annual risk of stroke was 1 percent. After TIA or minor stroke, warfarin reduced the annual risk of a second stroke from 12 percent to 4 percent. Aspirin had no such effect. The annual incidence of major bleeding episodes was 0.2-2.0 percent in the warfarin-treated subgroup, 0.2-1.5 percent in the aspirin subgroup and 0-1.6 percent in the placebo subgroup. Based on findings in the above mentioned trials, warfarin (INR 2.0-3.0) is recommended for stroke prevention in patients over 60 years of age with non-valvular atrial fibrillation. Trials are under way to ascertain whether conventional warfarin treatment can be replaced by less complicated and safer treatments in patients with chronic atrial fibrillation.