Conversion of recent-onset atrial fibrillation or flutter with ibutilide after amiodarone has failed

Objective: To evaluate whether ibutilide can convert atrial fibrillation or flutter in patients in whom antiodarone has failed. Design and setting: Clinical study in a university hospital intensive care unit (ICU). Patients: Twenty-six patients were studied, in whom atrial fibrillation or flutter persisted for a maximum of 6 h at maximum. Patients were monitored continuously during the arrhythmia. Medical conversion was necessary due to symptomatic or hemodynamic causes. Interventions: All patients initially received amiodarone (150 mg i.v.) and after 2 h of persistent arrhythmia ibutilide (1 mg or, without success and body weight >70 kg, 2 mg i.v.). Before the administration of ibutilide 1 g magnesium was administered, and high normal levels of potassium serum levels were achieved (4.5-5.0 mmol/1). Results:After amiodarone atrial flutter persisted in 73% and atrial fibrillation in 27% of patients. After ibutilide the QT interval was prolonged from 327+/-61 to 387+/-62 ms. The QTc interval increased from 456+/-32 to 461+/-66 ms. Conversion to normal sinus rhythm was achieved in 22 of 27 of cases. Nonsustained torsade de pointes tachycardia was seen in three patients (11%). No patient showed sustained ventricular tachycardia. Patients with proarrhythmic effects were characterized by a decreased left ventricular function. Conclusions: In ICU patients ibutilide led to conversion to sinus rhythm in 81.5% of patients in whom amiodarone was unsuccessful. Nonsustained tachycardias were seen in 11%; sustained ventricular tachycardia was not seen. Ibutilide seems to be well suitable for conversion of recent onset atrial fibrillation or flutter and had no severe side effects in this study population.