CONVERSION EFFICACY AND SAFETY OF INTRAVENOUS IBUTILIDE COMPARED WITHINTRAVENOUS PROCAINAMIDE IN PATIENTS WITH ATRIAL-FLUTTER OR FIBRILLATION

Objectives. This multicenter study compared the efficacy and safety of ibutilide versus procainamide for conversion of recent-onset atrial f lutter or fibrillation. Background. Ibutilide fumarate is an intraveno us (IV) class III antiarrhythmic agent that has been shown to be signi ficantly more effective than placebo in the pharmacologic conversion o f atrial flutter and fibrillation to sinus rhythm. Procainamide is com monly used for conversion of recent-onset atrial fibrillation to norma l sinus rhythm. Methods. One hundred twenty-seven patients (age range 22 to 92 years) with atrial butter or fibrillation of 3 h to 90 days' (mean 21 days) duration were randomized to receive either two 10-min I V infusions of 1 mg of ibutilide fumarate, separated by a 10-min infus ion of 5% dextrose in sterile water, or three successive 10-min IV inf usions of 400 mg of procainamide hydrochloride. Results. Of the 127 pa tients, 120 were evaluated for efficacy: 35 (58.3%) of 60 in the ibuti lide group compared with 11 (18.3%) of 60 in the procainamide group ha d successful termination within 1.5 h of treatment (p < 0.0001). Seven patients were found to have violated the protocol and were not includ ed in the final evaluation. In the patients with atrial flutter, ibuti lide had a significantly higher success rate than procainamide (76% [1 3 of 17] vs. 14% [3 of 22], p = 0.001). Similarly, in the atrial fibri llation group, ibutilide had a significantly higher success rate than procainamide (51% [22 of 43] vs. 21% [8 of 38], p = 0.005); One patien t who received ibutilide, which was found to be a protocol violation, had sustained polymorphic ventricular tachycardia requiring direct cur rent cardioversion. Seven patients who received procainamide became hy potensive, Conclusions. This study establishes the superior efficacy o f ibutilide over procainamide when administered to patients to convert either atrial fibrillation or atrial putter to sinus rhythm. Hypotens ion was the major adverse effect seen with procainamide. A low inciden ce of serious proarrhythmia was seen with the administration of ibutil ide occurring at the end of infusion. (C) 1998 by the American College of Cardiology.