Abstract 14300: Low-level Ganglionated Plexus (GP) Stimulation Facilitates Atrial Fibrillation: in vivo and in vitro Studies
Introduction: Clinical studies showed that GP ablation as an independent or adjunct strategy can increase the success rate of atrial fibrillation (AF) ablation not only in vagotonic AF patients but also in the other AF patients without noticeable increase in cardiac vagal tone. We hypothesized that long-term low level autonomic activation without marked change in sinus rate would cause significant alternations in atrial electrophysiology and contribute to AF. This study investigated the effects of six-hour low-level GP stimulation on atrial electrophysiological properties.
Methods: In 16 anesthetized open-chest dogs, electrodes on the anterior right GP and superior left GP allowed six-hour low level GP stimulation at 1 V below that which slowed the sinus rate or atrioventricular conduction. Multi-electrode catheters were fixed at the right and left superior and inferior PVs and both atria and atrial appendages. At the end of 3rd and 6th hour of low level GP stimulation, the effective refractory period (ERP) and window of vulnerability (WOV) for AF were measured at each site. The similar low-level stimulation (without myocardial capture) was delivered to the myocardium remote from GP for 6 hours in another 6 dogs for control. At the end of in vivo experiments, the ICa-L, IK-Ach and action potentials were recorded by patch-clamp.
Results: AF was not induced (WOV=0) in every case prior to low level GP stimulation. Six-hour low level GP stimulation induced a progressive shortening of ERP and increase in WOV at each site (p<0.05 for all). The spatial dispersion of ERP among the 8 sites was increased (p<0.05). The similar low level stimulation delivered to the myocardium remote from GP did not significantly change the ERP and WOV at any site. Patch-clamp experiments showed a significant shortening of action potential duration, a decrease in ion density of ICa-L, and an increase in IK-Ach, especially at the pulmonary veins, after six-hour of low level GP stimulation.
Conclusions: Six-hour low level GP stimulation induced significant changes in atrial electrophysiology and facilitated the initiation of AF, indicating that long-term low level autonomic activation without noticeable change in sinus rate would form electrophysiological substrate for AF.
- © 2010 by American Heart Association, Inc.