Efficacy and Safety of Repeated Intravenous Doses of Ibutilide for Rapid Conversion of Atrial Flutter or Fibrillation

Background Currently available antiarrhythmic drugs have limited efficacy for acute termination of atrial fibrillation and flutter, especially if the arrhythmia is not of recent onset. The purpose of this multicenter study was to determine the efficacy and safety of repeated doses of intravenous ibutilide, a class III antiarrhythmic drug, in terminating atrial fibrillation or flutter. Methods and Results Two hundred sixty-six patients with sustained atrial fibrillation (n=133) or flutter (n=133), with an arrhythmia duration of 3 hours to 45 days, were randomized to receive up to two 10-minute infusions, separated by 10 minutes, 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 efficacy (44% versus 49%). Efficacy was higher in atrial flutter than fibrillation (63% versus 31%, P<.0001). In atrial fibrillation but not flutter, conversion rates were higher in pat...