Aim of the study: To evaluate the effectiveness of Ibutilide in cardioversion of persistent atrial fibrillation in patients with sinus node disease wearing a dual chamber pacemaker and to assess the potential role of overdrive ventricular pacing in prevention of drug related proarrhythmia.
Methods and results: Fifty-three sinus node disease patients (35 males; mean age 75 +/- 9.5 years), implanted with a dual chamber pacing system, with persistent atrial fibrillation, lasting for 328 +/- 416 days, received 1-2 mg of intravenous Ibutilide. Pacing mode was programmed in VVI at 90 ppm, in order to suppress spontaneous ventricular activity. All patients were monitored for 4 hours. Late occurrence of ventricular arrhythmias was evaluated using the pacemaker memory. Ventricular pacing threshold, spontaneous electrogram amplitude and pacing impedance were measured before and after Ibutilide infusion. Cardioversion to sinus rhythm occurred in twenty-two patients (41.5%). Treatment success was significantly related to shorter atrial fibrillation duration. Paced QT interval duration increased from 412 +/- 36 ms to 481 +/- 40 ms (p < 0.0001), without differences between responders and non responders; QRS width did not change significantly (from 152 +/- 25 ms to 161 +/- 25 ms; p = n.s.). No early or late episodes of sustained or non sustained polymorphic ventricular tachycardia were observed. Pacing and sensing threshold did not show any significant variation.
Conclusions: Ibutilide showed a good effectiveness in treating persistent atrial fibrillation in paced patients. Overdrive ventricular pacing may have played a role in preventing drug induced ventricular proarrhythmia. No adverse effect on pacing threshold was observed.