Electrophysiology, pacing, and arrhythmia: Ibutilide: Efficacy and safety in atrial fibrillation and atrial flutter in a general cardiology practice

Abstract

Background: Published experience with ibutilide (IB) in randomized clinical trials reveals that conversion to sinus rhythm (SR) occurs in 31% of patients with atrial fibrillation (AF) and in 63% of patients with atrial flutter. 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, were treated with intravenous IB (0.4-2.0 mg). Duration of arrhythmia, left atrial (LA) size, ejection fraction (EF), time to conversion, QTc interval, and adverse drag events were determined. Patients were observed for a minimum of 6 h. Successful cardioversion was defined as arrhythmia termination within 6 h. Results: Twenty-four of 34 (70.6%) patients with AF and 15 of 20 (75%) patients with atrial flutter converted to SR. Conversion of AF to SR was more likely to occur if duration of AF was ∼ 96 h compared with > 96 h (81 vs. 17%, respectively; p = 0.006). The mean time to arrhythmia termination was 68.8 min. Left atrial size, determined by echocardiogram, was 44 ± 13 mm in 43 patients. Patients with LA size ∼ 45 mm had a conversion 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 predictor of drag success. The QTc intervals were significantly prolonged after IB administration, with a mean change of 47.1 ms for successfully treated patients. Sustained polymorphic ventricular tachycardia occurred in one patient within 1 min of IB infusion, requiring electrical cardioversion to SR. This patient's serum electrolytes and QTc interval were normal prior to IB infusion; however, the QTc increased by 160 ms (from 387 to 547 ms) during drug infusion. No systemic or pulmonary emboli occurred. Conclusion: The efficacy of IB for conversion of AF to SR in this prospective observational study was considerably better than previously reported. Duration of AF remains an important predictor of conversion to SR. Complications are rare and without long-term adverse effects.