Vagal stimulation prior to atrial rapid pacing protects the atrium from electrical remodeling in anesthetized dogs

Atrial electrical remodeling is thought to be the cause of the maintenance of atrial fibrillation (AF). Although the initiation and maintenance of AF is partially associated with autonomic nervous tone, vagally mediated A-F d oes not tend to become permanent. Therefore, the effects of preceding vagal stimulation (VS) on the atrial effective refractory period (ERP) under ele ctrical remodeling conditions were investigated in anesthetized dogs. Atria l ERPs were measured at 5 sites before and after a 7-h period of atrial rap id pacing in the control group. In the VS group, the vagus nerve was stimul ated for 20 min before a period of atrial rapid pacing. Atrial rapid pacing shortened the ERP at each site in the control group (electrical remodeling ). On the other hand, atrial rapid pacing after VS did not shorten the ERP at any site in the VS group. Tetrodotoxin, which was administered into the fatty tissue overlying the right atrial side of the fight pulmonary vein ju nctions, blocked the protective effect of VS against the shortening of the ERP induced by atrial rapid pacing. In contrast, atropine did not interfere with such protective effects. These results suggest that VS prior to atria l rapid pacing protects the atrium from atrial electrical remodeling.