Chronic atrial fibrillation. Success of serial cardioversion therapy and safety of oral anticoagulation

BACKGROUND: Serial electrical cardioversion is often used for treatment of atrial fibrillation, but its long-term efficacy has not been determined prospectively. OBJECTIVES: To determine the long-term success rate of the serial electrical cardioversion approach in patients with chronic atrial fibrillation, to identify factors that predict its success, and to assess the efficacy and safety of oral anticoagulation in these patients. METHODS: Patients with chronic (> 24 hours) atrial fibrillation received anticoagulant therapy for at least 4 weeks prior to electrical cardioversion. No prophylactic antiarrhythmic agent was given after the first shock. Relapses were managed by using repeated cardioversions, after which serial antiarrhythmic drug therapy was started. Treatment with anticoagulants was withdrawn after 4 weeks of sinus rhythm. RESULTS: Two hundred thirty-six patients were followed up for a mean +/- SD of 3.7 +/- 1.6 years. The actuarial cumulative percentages of patients who maintained sinus rhythm after serial cardioversion treatment was 42% and 27% after 1 and 4 years, respectively. Multivariate analysis showed that factors that were associated with failure of this approach included duration of atrial fibrillation that exceeded 36 months (risk ratio, 5.0; P < .001), poor exercise tolerance (functional class III; risk ratio, 1.8; P = .001), and age older than 56 years (risk ratio, 1.5; P = .04). The anticoagulation level (international normalized ratio, 2.4-4.8) was associated with an incidence of thromboembolic events and bleeding complications of 0.2% and 1.5%, respectively. CONCLUSIONS: Many patients with chronic atrial fibrillation failed to respond to the serial electrical cardioversion strategy. However, in younger patients with a fair exercise tolerance and a duration of atrial fibrillation shorter than 36 months, this approach may be worthwhile. In addition, thromboembolic events were infrequent in the patients who were subjected to this regimen.