Efficacy and Safety of Ibutilide for the Conversion of Monomorphic Atrial Tachycardia

BACKGROUND: Ibutilide is a class III antiarrhythmic drug, frequently used for conversion of atrial fibrillation and flutter. We studied the efficacy of ibutilide for acute conversion of monomorphic atrial tachycardia (monoAT) in a prospective, open label study in the intensive care unit of a cardiological clinic. METHODS: We examined 49 episodes of monoAT in 38 patients (19 men/19 women). Thirty-three patients (87%) suffered from structural heart disease. Twenty-three episodes occurred while on antiarrhythmic therapy with class I or III drugs. Patients with prolonged QT interval (except for patients with pretreatment with class III drugs), hypokalemia, left ventricular failure, and recent myocardial infarction were excluded. All patients received one or two doses of 1 mg ibutilide fumarate under continuous rhythm monitoring. RESULTS: Conversion to sinus rhythm occurred in 19 episodes (38.8%), in 6 episodes (12.2%) after the first dose. Conversion rate was significantly higher in patients with a short history of symptoms (66.6% vs 28.6%; P < 0.05), of documented arrhythmia (0.13 (0/5.7) vs 2.6 (0.38/23.5) months, median (interquartile range); P < 0.03), higher atrial rate (272 +/- 49 vs 207 +/- 36 beats/min (means +/- SD); P < 0.004), or without preexisting antiarrhythmic therapy (53.8% vs 21.7%; P < 0.02). No differences in conversion rates were found regarding gender, age, body mass index, left ventricular function, left atrial diameter, or underlying disease. In three episodes torsade de pointes occurred after ibutilide (6.1%), requiring defibrillation in two cases (4.1%). CONCLUSIONS: Ibutilide can be used for conversion of monoAT with a similar efficacy as for atrial fibrillation, but with a considerably lower efficacy compared to typical atrial flutter.