Chemical Cardioversion of Atrial Fibrillation or Flutter With Ibutilide in Patients Receiving Amiodarone Therapy

Abstract

Background-Ibutilide is a class III drug that is used for the cardioversion of atrial arrhythmias, but it can cause torsade de pointes. Amiodarone also 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 purpose of the present study was to assess the efficacy and safety of cardioversion with combination therapy in patients with atrial fibrillation or flutter. Methods and Results-The study included 70 patients who were treated with long-term oral amiodarone and were referred for elective cardioversion of atrial fibrillation (57 of 70, 81%) or flutter (13 of 70, 19%). Patients were taking amiodarone (153Ϯ259 days, meanϮSD) and were administered 2 mg intravenous ibutilide. Left ventricular ejection fraction was measured with echocardiography. The QT intervals were measured on 12-lead ECG. Fifty-five patients (79%) had structural heart disease. Patients were in arrhythmia for 196Ϯ508 days before cardioversion, with a left ventricular ejection fraction of 50Ϯ11%. In patients with atrial fibrillation, 22 (39%) of 57 and 7 (54%) of 13 patients with flutter converted within 30 minutes of infusion. Thirty-nine patients who did not convert after ibutilide were treated with electrical cardioversion, and 35 (90%) of 39 patients were successfully converted. The QT intervals were further prolonged after ibutilide for the group from 371Ϯ61 to 479Ϯ92 ms (PϽ0.001). There was 1 episode of nonsustained torsade de pointes (1 of 70, 1.4%) after ibutilide. Conclusions-The use of ibutilide converted 54% of patients with atrial flutter 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 combination therapy may be a useful cardioversion method for chronic atrial fibrillation or flutter.

Electrophysiologic and Antiarrhythmic Effects of AZD1305 in Canine Pulmonary Vein Sleeves

“…Whether amiodarone-treated patients can be safely converted with any repolarization-delaying agent is still unclear. A few clinical studies have demonstrated that restoration of sinus rhythm by ibutilide in patients receiving amiodarone is as safe (and effective) as the use of ibutilide alone (Glatter et al, 2001;Fragakis et al, 2005). In the canine left ventricle, long-term treatment with amiodarone differentially altered the cellular electrophysiology of the ventricular myocardium such that the transmural dispersion of repolarization decreased (Sicouri et al, 1997).…”

Conversion of recent-onset atrial fibrillation or flutter with ibutilide after amiodarone has failed

“…It has been shown that ibutilide administration in patients under long-term treatment with amiodarone does not increase proarrhythmia (1.4%). Conversion rates of 54% for atrial flutter and 39% for atrial fibrillation have been achieved in these patients [12].…”

Safety and Efficacy of Ibutilide in Cardioversion of Atrial Flutter and Fibrillation

“…Because of the long half-life of amiodarone it is often not feasible to discontinue it before ibutilide administration; both of these drugs are class III antiarrhythmic agents and the prolongation of the QT interval could result in proarrhythmia. Glatter et al 22 addressed this concern of the increased incidence of proarrhythmia. In their study, which assessed the efficacy and safety of cardioversion with combination therapy in patients with atrial fibrillation or flutter, it was found that within 30 minutes of infusion, ibutilide converted 54% of patients with atrial flutter and 39% of patients with atrial fibrillation who had been treated with long-term amiodarone.…”

“…The use of ibutilide was found to be safe in these patients, with no excess occurrence of proarrhythmia. 22 Ibutilide pretreatment also has been found to facilitate successful electrical cardioversion. Ibutilide significantly facilitates cardioversion of atrial fibrillation with standard monophasic transthoracic defibrillation.…”