Ibutilide: Efficacy and safety in atrial fibrillation and atrial flutter in a general cardiology practice

Background: Published experience with ibutilide (IB) in randomized clinical trials reveals that conversion to sinus rhythm (SR) occurs in 31% of patie nts with atrial fibrillation (AF) and in 63% of patients with atrial flutte r. Hypothesis: The study was undertaken to test the efficacy and safety of IB in patients with AF and with atrial flutter and to compare them with those reported in previous studies. Methods: In a general cardiology practice, 54 consecutive patients with AF or atrial flutter, no contraindication to IB, and a normal QTc interval, we re treated with intravenous IB (0.4-2.0 mg). Duration of arrhythmia, left a trial (LA) size, ejection fraction (EF), time to conversion, QTc interval, and adverse drug events were determined. Patients were observed for a minim um of 6 h. Successful cardioversion was defined as arrhythmia termination w ithin 6 h. Results: Twenty-four of 34 (70.6%) patients with AF and 15 of 20 (75%) pati ents with atrial flutter converted to SR. Conversion of AF to SR was more l ikely to occur if duration of AF was similar to 96 h compared with > 96 h ( 81 vs. 17%, respective ly; p = 0.006). The mean time to arrhythmia terminat ion was 68.8 min. Left atrial size, determined by echocardiogram, was 44 +/ - 13 mm in 43 patients. Patients with LA size similar to 45 mm had a conver sion rate of 55% in both AF and flutter, compared with a conversion rate of 72% in patients with LA size < 45 mm. Ejection fraction was not a predicto r of drug success. The QTc intervals were significantly prolonged after IB administration, with a mean change of 47.1 ms for successfully treated pati ents. Sustained polymorphic ventricular tachycardia occurred in one patient within 1 min of IB infusion, requiring electrical cardioversion to SR. Thi s patient's serum electrolytes and QTc interval were normal prior to IB inf usion; however, the QTc increased by 160 ms (from 387 to 547 ms) during dru g infusion. No systemic or pulmonary emboli occurred. Conclusion: The efficacy of IB for conversion of AF to SR in this prospecti ve observational study was considerably better than previously reported. Du ration of AF remains an important predictor of conversion to SR. Complicati ons are rare and without long-term adverse effects.