Prevention of thromboembolism in patients with atrial fibrillation.

New insights into atrial physiology based on observations using transesophageal echocardiography are presented. The approach to anticoagulation of patients with both acute and chronic atrial fibrillation is reviewed within the context of the results of the major multicenter trials. These have provided some useful risk stratification guidelines for therapy. Presently available data suggest that the role of transesophageal echocardiography as a precardioversion screen is promising but requires further definition through clinical trials.