ATRIAL FIBRILLATION
Increased AAI mode pacing threshold after termination of atrial fibrillation by acute administration of disopyramide phosphate
1 Division of Cardiology, Department of Internal Medicine, Jikei University School of Medicine, 3-25-8 Nishi-Shimbashi, Minato-ku, Tokyo 105-8461, Japan; 2 Department of Internal Medicine, Tsunan Hospital, Niigata, Japan
Aims We studied changes in atrial pacing threshold after termination of atrial fibrillation (AF) by acute administration of disopyramide phosphate (DP) to elucidate the suitable setting for atrial pacing output before AF termination.
Methods and results Four patients with sick sinus syndrome implanted with AAI mode pacemakers were examined. Disopyramide phosphate (2 mg/kg body weight) was injected intravenously for termination of a total of eight AF episodes. The maximal pacing threshold after AF termination (5.2±0.8 V at 0.45 ms) was significantly higher than that at baseline (1.3±0.2 V at 0.45 ms; P<0.01) and the average increment was 433±68%. During a period free from AF, an acute administration of DP did not increase the atrial pacing threshold and serum disopyramide levels were not toxic.
Conclusion The increased atrial pacing threshold observed after AF termination cannot be explained by the action of DP alone. However, our results suggest that atrial pacing output should be set at the maximum value before DP is administered to induce AF termination in patients with AAI pacemaker-dependent bradyarrhythmias.
Key Words: Antiarrhythmic drug, Atrial fibrillation, Disopyramide phosphate, Pacing failure, Pacing threshold, Sick sinus syndrome
* Corresponding author. Tel: +81 3 3433 1111 ext. 3261 or 3262; fax: +81 3 3459 6043. E-mail address: anzawar{at}jikei.ac.jp