[Pathophysiology and prevention of cardiogenic brain embolism]

Cardiogenic brain embolism (CBE) accounts for approximately 20% of symptomatic ischemic stroke patients in Japan. Nonvalvular atrial fibrillation (NVAF) is the most common cause of CBE, accounting for approximately 50%. As compared to other ischemic stroke subtypes such as lacunar and atherothrombotic infarction, CBE is accompanied by more extensive infarction and more pronounced brain edema. Reopening of an occluded artery, that may cause hemorrhagic transformation (40%) or exacerbate brain edema, is frequently observed (60 to 90%). Early mortality and recurrence rates are high, and outcome is often poor. Patients with CBE older than 70 years have NVAF more frequently (76%) and their outcome is worse as compared to the younger CBE patients. In North American and European countries, warfarin with the intensity of 2.0 to 3.0 (or 4.0) is recommended for NVAF patients with advanced age, hypertension, history of brain infarction, or other high-risk features. Our prospective, randomized study, however, indicated that the low-intensity warfarin (INR 1.5 to 2.1) may be safer than the conventional-intensity treatment for the secondary prevention of stroke in CBE patients with NVAF, especially in old ones. Prospective, randomized trials must be conducted to establish the optimal treatment strategy in primary prevention of stroke in Japanese persons with NVAF.