e0018 Vagus nerve-mediated electrical remodelling of pulmonary veins in chronic atrial pacing dogs with or without superior vena cava and aortic root fat pad

Objectives We aim to elucidate the relationship between vagus nerve and the electrical remodelling of pulmonary veins in vagus nerve-mediated atrial fibrillation dogs. Methods 24 adult mongrel dogs weighing 15–20 Kg were randomly divided into sham operation group (S group, n=8), SVC-Ao fat pad removal group (R group, n=8) and SVC-Ao fat pad reserved group (Re group, n=8). After exposure of superior vena cava and aortic root fat pad, SVC-Ao fat pad was excised in R group dogs, and sewed epicardial pacing lead into high right atrium and successively paced for 6 weeks; for Re group dogs, suture of epicardial pacing leads and pace for 6 weeks, take the sham operation dogs as control. To detect the Left Superior Pulmonary Vein, Right Superior Pulmonary Vein, Left Inferior Pulmonary Vein, Right Inferior Pulmonary Vein respectively, including Sinus Cycle Length (SCL), Effective Refractory Period (ERP), dispersion of ERP (dERP), and the expression of Cx40 and Cx43 by Western Blot, observed the distribution of gap junctions at pulmonary vein sleeves by immunofluorescence and electron microscope. Results One dog in R group died for anaesthesia, another dog in Re group had pacemaker problem that required us to remove them from the study. The SCL shortened after pacing (510±24 ms vs 430±18 ms, 380±26 ms, p<0.05), ERP shortened (146±18 ms vs 125±18 ms, 115±19 ms, p<0.01), dERP increased. The expression of Cx40 increased significantly in both experiment groups (1017.23±314.46 Int×mm2 vs 1709.43±429.88 Int×mm2, 2956.05±829.38 Int×mm2 p<0.01), the expression of Cx43 increased significantly in above groups (915.21±338.93 Int×mm2 vs 1859.94±412.11 Int×mm2, 3048.83±931.35 Int×mm2, p<0.01). The length and width of GJ in pulmonary vein sleeves shortened (L: 0.381±0.034 μm vs 0.390±0.117 μm, 0.260±0.069 μm; W: 23.29±3.70 nm vs 22.38±2.46 nm, 18.54±2.56 nm, p<0.05), and the Termination/Side (T/S) ratio of Cx40 and Cx43 decreased (Cx40: 1.34±0.11 vs 1.16±0.07, 0.98±0.06; Cx43: 1.27±0.09 vs 1.10±0.07, 0.90±0.09, p<0.05). Conclusions The vagus nerve originated from SVC-Ao fat pad plays a role in pulmonary vein reconstitution, and these are part of basal elements for the development and maintenance of experimental atrial fibrillation.