[Anticoagulation in atrial fibrillation].

Atrial fibrillation is the most common arrhythmia in the elderly and is associated with substantial morbidity and mortality, mostly due to the consequences of thromboembolism. Anticoagulation reduces the risk of stroke and death considerably, the risk reduction depending on the patient's absolute risk. Although there is modest benefit from acetylsalicylic acid, randomized trials have shown that it is consistently and substantially less effective than vitamin K antagonists. These benefits must be balanced against an increased risk of bleeding. In addition, warfarin therapy imposes a variety of lifestyle constraints, including frequent blood test monitoring and, possibly, dietary modification, and is associated with a number of drug interactions. Careful assessment of the absolute risk of stroke on the one hand and bleeding complications on the other hand will guide the use of appropriate prophylaxis against thromboembolism and its consequences.