ABSTRACT
Background Atrial electrical remodeling(AER)plays an important role in the pathogenesis and maintenance of atrialfibrillation.However,little is known about modulation of vagal activilty to AER.This study aimed to investigate the relationshipbetween vagal moduation and AER. Methods Twenty four adult mongrel dogs under general anesthesia were randomized into 3groups.Sympathetic activity was blocked by administration of metoprolol in 3 groups.The changes in vagal modulation to atria afterAER were observed in 10 dogs without vagal interruption in group A.The effects of vagal intervention on AER were investigated in 8dogs with administration of atropine in group B.The impact of aggressively vagal activity on AER was studied in 6 dogs with bilateralcervical vag sympathetic trunLks stimulation during AER in group C.Bilateral cervicall vagosympathetic trunks were decentralized.Multipolar catheters wereplaced into high right atria(RA),coronary sinus(CS)and rightventricle(RV).AER was induced by 600 bpmpacing through RA catheter for 30 minutes.Attial effective refractory period(ERP)and vulnerability window (VW)of atrial fibrillationwere measured with and without vagal stimulation before and after AER.Results In group A,ERP decreased significantly at baselineand during vagal stimulation after AER compared with that beforeAER(all P＜0.05).In group B,ERP remaind unchanged at baselineand vagal stimulation after AER compared with tbat before AER (all P＞0.05).In group C,ERP shortened significantly at baseline andvagal stimulation after AER compared with that before AER(all P＜0.05).ERP shortening after AER in Groups A and C increasedsignificantly than that in group B (all P＜0.05).Atrial fibrillation could not be induced at baseline(VW close to 0) before and after AERin three groups.VW became widen significantly during vagal stimulation after AER compared with that before AER in Groups A and C(all P＜0.05),while VW remained unchanged in group B (VW close to 0).Conclusions Short-term AER results in the decrease inERP.AER is accompanied by the increases in atrial vagal modulation.The increased vagal activity and vagal stimulation promote AER,thereby increase the susceptibility to atrial fibrillation.The interrupted vagal activity attenuates AER.thereby suppresses the atriaIfibrillation mediated by vagal stimutlation.