Objective To investigate the mechanism of influence of network between cervical vagus trunk and fat pads on sinus node function, ERP of atria and pulmonary veins and inducibility and maintenance of atria fibrillation.

Methods 7 dogs, of weight 14 to 18 kg, were placed under anaesthesia using sodium pentothal 30 mg/kg, midazolam 0.4 mg/kg IV and 0.05 mg/kg/h. Bipolar electrode catheters were placed into the right atrial, right ventricular and bundle branch for mapping and stimulating. The hearts were exposed via right thoracotomy to expose the SAN-FP (sinus-atrial node fad pad) and AVN-FP (atria ventricular node fad pad). Bipolar electrodes and ten-polar electrodes were fixed on the left atrial appendage and the pulmonary veins. Comparison of sinus rate (SR), effective refractive period (ERP) of atrial and pulmonary vein, and both inducibility and maintenance of atrial fibrillation were performed before and after sequential ablation of SAN-FP and AVN-FP.

Results (1) The heart rate (HR) decreased significantly from 133.0±13.5 ms and 130.0±15.9 ms to 32.6±20.4 ms and 85.6±33.2 ms by stimulating right and left cervical vagus trunk, respectively, and HR decreased slightly from 125.2±21.3 ms to 102.5±4.94 ms by stimulation of SAN-FP, while HR was not affected by stimulating AVN-FP. The effect of stimulating cervical vagus trunk on reducing HR was partially expressed with SAN-FP ablation and totally eliminated by SAN-FP+AVN-FP combined ablation. (2) The ERP and increased ERP dispersion of atrial and pulmonaries were significantly by stimulating SAN-FP and abolished by ablating SAN-FP, while no big difference of ERP and ERP dispersion in atrial and pulomonaries was recorded when stimulation and ablation was exerted on AVN-FP; (3) Pacing at right atrial with 600 bpm, the AF was induced 60% and 18.4% by stimulating right and left cervical vagus trunk as well as 15.29% and 2.25% by stimulating SAN-FP and AVN-FP. However, with the stimulating at right and left cervical vagus trunk, the inducibility of AF was reduced to 16.8% and 6% when SAN-FP had ablated and even to 0% when AVN-FP had ablated.

Conclusion We concluded that sinus node function was adjusted mainly by stimulating at right cervical vagus trunk through AVN-FP. The shorted ERP and increased ERP dispersion of atrial and pulmonary as well as AF were induced by stimulating cervical vagus trunk mainly coordinated with AVN-FP. Our study strongly suggested that AVN-FP is a very important coordinator in relation to parasympathetic dominant AF.