Effect of verapamil on long-term tachycardia-induced atrial electrical remodeling

Background-The effect of verapamil on long-term tachycardia-induced atrial electrical remodeling has not been reported. Methods and Results forty-eight dogs were randomly divided into verapamil a nd control groups. The dogs in the verapamil group received verapamil 120 m g every day, those in the control group did not receive verapamil. Atrial e ffective refractory period (AERP), inducibility of atrial fibrillation (AF) , and duration of AF were assessed before and after complete atrioventricul ar junction ablation with 1-day, 1-week, or 6-week rapid atrial pacing (780 bpm). AERP shortening, AERP dispersion, AERP maladaptation, and inducibili ty of AF after 1-day pacing was significantly attenuated by verapamil. Howe ver, verapamil did not have any significant effect on these parameters in t he dogs with 1-week or 6-week pacing. Verapamil did not have any significan t effect on the conduction velocity in the dogs with 1-day, 1-week, or 6-we ek pacing. Before rapid atrial pacing, verapamil significantly prolonged th e duration of AF. In the dogs with 1-day pacing, the duration of AF measure d immediately after termination of pacing was similar between the control a nd verapamil groups. However, in the dogs with 1-week or 6-week pacing, the duration of AF after pacing was significantly longer in the verapamil grou p. Conclusions-Verapamil cannot prevent long-term (1 and 6 weeks, respectively ) tachycardia-induced changes of atrial electrophysiological properties. Fu rthermore, verapamil increases the duration of AF in the dogs either before or after long-term rapid atrial pacing.