[Anticoagulation in cardioversion of atrial fibrillation. Current status and outlook for the future]

Atrial fibrillation is the most common arrhythmias with increasing incidence in the elderly. The increased morbidity associated with atrial fibrillation is mainly caused by cardiac emboli, mostly from the left atrial appendage, that may cause cerebral ischemic infarctions. Although electrical cardioversion of atrial fibrillation has been the standard therapy for restoration of sinus rhythm for many years, questions regarding the optimal anticoagulation for the prevention of thromboembolic complications remain unanswered.

Current guidelines advocate the use of oral anticoagulation (adjusted to an Internal Standardized Ratio [INR] of 2.0-3.0) for at least 3-4 weeks before cardioversion for atrial fibrillation of > 48 h duration. Because of the atrial contractice dysfunction following cardioversion, the so-called "atrial stunning", anticoagulation for another 3-4 weeks after cardioversion is recommended. Alternatively, early cardioversion using high-dose intravenous heparin after exclusion of intraatrial thrombi by transesophageal echocardiography is possible, also followed by 3-4 weeks of oral anticoagulants. Because of the fear of bleeding complications, these anticoagulation schemes are frequently underused in the clinical setting, especially in older patients. Thus, new therapeutic approaches for anticoagulation in the setting of cardioversion are currently being investigated.

Low molecular weight heparins allow outpatient therapy because no intravenous therapy initiation is necessary and the need for anticoagulation monitoring is reduced. Whether oral thrombin antagonists may increase the safety of chronic anticoagulation because of their higher therapeutic index compared to warfarin has to be determined in future studies.