Thromboembolic complications of atrial fibrillation and their prevention: a review.

Atrial fibrillation (AF) is found in 0.4% of adults younger than age 60 years and in 2 to 4% older than age 60 years, and is associated with a high risk of thromboembolic complications. AF--paroxysmal and chronic--has many etiologies, including rheumatic and nonrheumatic heart disease and thyrotoxicosis. Knowing how strokes occur and what precipitates them--e.g., differentiating between cardioembolic and cerebrovascular causes--is important when deciding on appropriate treatment. Risk factors involved in the development of thromboembolic complications associated with AF are reviewed, focusing on the contributions of thyrotoxic AF, paroxysmal AF (and its transition to chronic AF), enlargement of the left atrium, silent cerebral infarction and decreased cerebral blood flow. Data from several studies are briefly presented, highlighting major outcomes. On the basis of current information about prevention of thromboembolic complications, it seems reasonable to recommend anticoagulant treatment for patients with nonrheumatic chronic AF.