[Primary prevention of thrombosis for patients with atrial fibrillation]

Clinical importance of antithrombotic prophylaxis strategy for patients with atrial fibrillation has been focused because of the high prevalence of severe cerebral embolism especially in elderly patients. Several multicenter, randomized clinical trials for prevention of thromboemblolism performed in the Western countries have revealed efficacy of the anticoagulation therapy with warfarin over the anti-platelet aggregation therapy with aspirin. Therapeutic guideline for thromboembolism in patients with atrial fibrillation has been established based on these observations. However, special attentions should be paid for applying the guideline for Japanese patients since bleeding risk in antithrombotic treatment seems to be high in Japanese. Recently, therapeutic guideline for thromboembolism in Japanese patients with atrial fibrillation has been established. In this guideline, treatment with warfarin is also recommended for patients with atrial fibrillation. However treatment target of warfarin, ie, PT-INR, is designated rather low in Japanese patients, especially in eldely patients over 75 years old. Usage of antiplatelet treatment with aspirin is also described in this guideline for Japanese, however, the evidence suggesting the usefulness for prophylaxis with aspirin is not sufficiently obtained in Japanese patients. Further clinical studies for antithrombotic treatment are needed for Japanese patients with atrial fibrillation.