Abstract
Given the clinical interest concerning 'reflex vagal' responses to identify left atrial (LA) targets for ablative therapy of atrial fibrillation, we investigated whether vagal and bilateral atrial neural pathways may be involved in chronotropic and atrial repolarization responses to LA ganglionated plexus (GP) stimulation. Unipolar electrograms were recorded from 191 right atrial (RA) and LA sites in anaesthetized canines prior to and during electrical stimulation of the right vagus nerve (VgN), left VgN, or LAGP at baseline and following (i) bilateral VgN decentralization, and radiofrequency ablation of (ii) periaortic/superior vena cava (Ao/SVC) and (iii) RAGP in 14 animals (anterograde group), and in the reverse order in 7 (retrograde). Repolarization changes were also measured in similar preparations during Ao/SVC (n = 8) and RAGP stimulation (n = 23). Sinus cycle length (SCL) prolongation, and RA and LA repolarization changes (affected atrial surface area) were induced during LAGP stimulation. SCL prolongation and RA repolarization changes were unaffected by VgN decentralization but reduced following Ao/SVC and RAGP ablation in the anterograde group. In the retrograde group, chronotropic and RA repolarization changes were reduced following RAGP and abolished following Ao/SVC ablation. In contrast, LA repolarization responses to LAGP stimulation were reduced following VgN decentralization and each subsequent ablation step, with small residual responses after completing the anterograde protocol. Ao/SVC and RAGP stimulation exerted predominant influences in adjacent regions as well as demonstrating LA extensions. Vagal as well as bilateral atrial neural pathways are involved in mediating chronotropic and LA repolarization responses to LAGP stimulation.
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