EFFICACY AND SAFETY OF REPEATED INTRAVENOUS DOSES OF IBUTILIDE FOR RAPID CONVERSION OF ATRIAL-FLUTTER OR FIBRILLATION

Background Currently available antiarrhythmic drugs have limited effic acy for acute termination of atrial fibrillation and flutter, especial ly if the arrhythmia is not of recent onset. The purpose of this multi center study was to determine the efficacy and safety of repeated dose s of intravenous ibutilide, a class III antiarrhythmic drug, in termin ating atrial fibrillation or flutter. Methods and Results Two hundred sixty-six patients with sustained atrial fibrillation (n=133) or flutt er (n=133), with an arrhythmia duration of 3 hours to 45 days, were ra ndomized to receive up to two 10-minute infusions, separated by 10 min utes, of ibutilide (1.0 and 0.5 mg or 1.0 and 1.0 mg) or placebo. The conversion rate was 47% after ibutilide and 2% after placebo (P<.0001) . The two ibutilide dosing regimens did not differ in conversion effic acy (44% versus 49%). Efficacy was higher in atrial flutter than fibri llation (63% versus 31%, P<.0001). In atrial fibrillation but not flut ter, conversion rates were higher in patients with a shorter arrhythmi a duration or a normal left atrial size. Arrhythmia termination occurr ed a mean of 27 minutes after start of the infusion. Of 180 ibutilide- treated patients, 15 (8.3%) developed polymorphic ventricular tachycar dia during or soon after the infusion. The arrhythmia required cardiov ersion in 3 patients (1.7%) and was nonsustained in 12 patients (6.7%) . Conclusions Intravenous ibutilide given in repeated doses is effecti ve in rapidly terminating atrial fibrillation and flutter and under mo nitored conditions is an alternative to current cardioversion options.