| Objective: To investigate the effects on the electronic remodel of atrium and pulmonary vein and atrial fibrillation(AF) induced by rapid atrial pacing and vagus nerve.Methods: (1)Electrophysiologic chanage of canine atria and pulmonery vein(PV) and inductive incidence of paroxysmal AF with or without bilatalal cervical vagal stimulation were examined before and afther atropine administration or removing of SVC-AO fat pad. (2)The changes of ectrophysiology were observed after sixteen auto-randomized controlled canines were subjected to 1 hour of atrial pacing at 600 ppm with or without removing of SVC-AO fat pad. (3)Eectrophysiology of atria and PV and inductive incidence of AF of canine were examined before and after canines were subjected to 6 weeks of atrial pacing at 600 ppm with or without removing of SVC-AO fat pad.Results: (1)There were significant increase in sinus cycle length(SCL), and decrease in effective refractory period(ERP) of atria and PV, and increase in dispersion of the atrial effective refractory period (dAERP) and in inductive rate and duration of paroxysmal AF without removing of SVC-AO fat pad compared with removing of SVC-AO fat pad while bilatalal cervical vagal stimulation. (2)There were significant decrease in ERP and increase in dAERP after cessation of the 1 hour of atrial rapid pacing without removing of SVC-AO fat pad, and dAERP was becoming an increasing in a long-time. After removing of the SVC-AO fat pad, the shortening of ERP was reduced and the dAERP was effectivelly inhibited during the atrial rapid pacing. (3) SVC-AO fat pad group: there were significant decrease in ERP, and increase in dAERP and in inductive rate of paroxysmal AF and persistent AF, and increase in duration of paroxysmal AF after cessation the 6 weeks of atrial rapid pacing. With removing of group: there decrease in ERP and inrease in duration of paroxysmal AF after cessation of the 6 weeks of atrial rapid pacing, and there were no change in dAERP and in inductive rate of paroxysmal AF, persistent AF was not successfully induced in all canines.Conclusions: (1)Vagal tone could be increased by bilatalal cervical vagal stimulation, which resulted in the atrial and PV electrial remodeling,and removing of SVC-AO fat pad can inhibit this effect. (2)Rapid atrial pacing could increase vagal tone, and resulted in the atrial and PV electrial remodeling, and removing of SVC-AO fat pad could effectivelly reduce and inhibit the atrial and PV electrial remodeling. (3)Vagal nerve mediate the persistent atrial fibrilationg induced by rapid atrial pacing. (4)The study suggests that we can possibilly reduce the development of vagal nerve mediated AF by romoving of the SVC-AO fat pad or ablationing of it. |
