Chemical cardioversion of atrial fibrillation or flutter with ibutilide inpatients receiving amiodarone therapy

Backgrould-Ibutilide is a class III drug that is used for the cardioversion of atrial arrhythmias, but it can cause torsade de pointes. Amiodarone als o prolongs the QT interval but rarely causes torsade de pointes. There are no studies in which the concomitant use of the 2 agents was examined. The p urpose of the present study was to assess the efficacy and safety of cardio version with combination therapy in patients with atrial fibrillation or fl utter. Methods ann Results-The study included 70 patients who were treated with lo ng-term oral amiodarone and were referred for elective cardioversion of atr ial fibrillation (57 of 70, 81%) or flutter (13 of 70, 19%). Patients were taking amiodarone (153+/-259 days, mean+/-SD) and were administered 2 mg in travenous ibutilide. Left ventricular ejection fraction was measured with e chocardiography. The QT intervals were measured on 12-lead EGG. Fifty-five patients (79%) had structural heart disease. Patients were in arrhythmia fo r 196+/-508 days before cardioversion, with a left ventricular ejection fra ction of 50+/-11%. In patients with atrial fibrillation, 22 (39%) of 57 and 7 (54%) of 13 patients with flutter converted within 30 minutes of infusio n. Thirty-nine patients who did not convert after ibutilide were treated wi th electrical cardioversion, and 35 (90%) of 39 patients were successfully converted. The QT intervals were further prolonged after ibutilide for the group from 371+/-61 to 479+/-92 ms (P<0.001). There was 1 episode of nonsus tained torsade de pointes (I of 70, 1.4%) after ibutilide. Conclusions-The use of ibutilide converted 54% of patients with atrial flut ter and 39% Of patients with atrial fibrillation who were treated with long -term amiodarone, Despite QT-interval prolongation after ibutilide, only 1 episode of torsade de pointes occurred. Our observations suggest that combi nation therapy may be a useful cardioversion method for chronic atrial fibr illation or flutter.