Abstract 2622: The Left Atrial Ganglionated Plexus - Its Function and Pathways Relative to Atrial Fibrillation Surgery
Introduction: The epicardic ganglionated plexi of the cardiac autonomic nervous system have recently become the target of ablative therapy in the treatment of atrial fibrillation. To identify circuits responsible for the bradycardic response to electrical stimulation of the left atrial ganglionated plexus (LAGP), antegrade and retrograde sequential ablations of presumed autonomic pathways were performed.
Methods: Twenty-two bilaterally thoracotomized canines were instrumented with atrial epicardial 191 unipolar electrode plaques. Regional effects of neural stimulation were assessed by repolarization changes (REPOLΔ) as measured on each atrial electrogram. LAGP stimulation was performed in the basal state and successively following
radiofrequency ablation of the peri-aortic/superior vena caval (AO/SVC) plexi, and
of the right atrial ganglionated plexus (RAGP), in this order (antegrade) or in the reversed order.
Results: In 17 animals (77%), LAGP stimulation induced a sinus bradycardia (151±36 vs 137±29 bpm, p<0.002). In the antegrade group (N=12), response was suppressed by vagal decentralization (N=1), AO/SVC plexi ablation (N=4), and RAGP ablation (N=5), and persisted throughout in 2 canines. At each ablation stage, surface area of LAGP induced REPOLΔ diminished with successive denervation: from 405±226mm2 in the basal state to 239±192mm2 with decentralisation (p<0.05), to 278±193 mm2 with AO/SVC ablation (p<0.04), and to 41±86mm2 following RAGP ablation (p<0.04). With retrograde denervation, bradycardic changes were suppressed following RAGP ablation in 2 canines, and following AO/SVC ablation in the remaining 3.
Conclusion: This data demonstrates that
the LAGP can be identified intraoperatively by the bradycardic response to direct stimulation in most cases;
this response corresponds to neurophysiological repolarization effects on the atria;
LAGP-sinus node connections do not depend on a central extrathoracic vagal reflex but rather multiple epicardial and intracardiac pathways.
These results may have important clinical implications relating to ablative treatment of atrial fibrillation, particularly if the LAGP were shown to harbour neurons with arrythmogenic potential.