Oral verapamil attenuates the progression of pacing-induced electrical and mechanical remodeling of the atrium

Background: Calcium overload plays a major role in the development of electrical and mechanical remodeling during atrial fibrillation, but the potential of verapamil, a Ca blocker, for preventing atrial electrical remodeling remains controversial. Methods and Results: Pacing and recording electrodes were sutured to the right atrium in 16 dogs. After a 5-day recovery period, rapid atrial pacing at 400 ppm was initiated in 8 dogs (control group). In the remaining 8 dogs, oral administration of verapamil (8 mg/kg per day) was started 1 week before the initiation of rapid pacing (verapamil group). On the day before and at 2, 7, 14 days after rapid pacing, electrophysiological (EP) and transesophageal echocardiographic (TEE) studies were performed under autonomic blockade. In response to rapid pacing, EP and TEE parameters changed progressively in the control group (p<0.05 vs day 0), whereas in the verapamil group, no significant changes in the various parameters were observed for the first 7 days. However, verapamil failed to prevent progression of both types of remodeling after 14 days of pacing. Conclusion: Verapamil can attenuate the progression of electrical and mechanical remodeling of the atrium for at least 7 days.