| Objective:Recently,it has been found that ablation the vein of Marshall(VOM)can further improve the success rate of atrial fibrillation ablation(AF).The VOM is a branch of coronary vein,which runs on the posterior wall of left atrium and is adjacent to the left ganglionated plexus(LSGP).Amount of autonomic nerve fibers were distributed in the VOM.Stimulation the VOM result in increased tension of vagus nerve,such as sinus brady.The mechanism of alcohol ablation the vein of Marshall in the treatment of AF may be related to the removal of vagus.In addition,low-level stimulation of vagus nerve can be used to inhibit the local inducibility of the AF.The aim of this study was to investigate the effects of low-level stimulation and anhydrous alcohol infusion of VOM on vagal function and inducibility to AF in dogs.Methods: Seven adult mongrel dogs weighing 10-15 kg were anesth etized with Na-pentobarbital,30mg/kg,and ventilated with room air by a positive pressure respirator.Both cervical vagosympathetic trunks were exposed by surgical dissections.The proximal brain was ligated.Propranolol was used to block the sympathetic nerve activity.The left superior pulmonary vein(LSPV),left inferior pulmonary vein(LIPV),left atrial appendage(LAA)exposed and sutured to fix the electrode catheter.The indwelling was inserted into the VOM.Two stimulation electrodes were inserted into VOM and LSGP respectively.In basic state,LSGP was stimulated,LSGP was stimulated with low-level stimulation of VOM,as well as the LSGP was stimulated after atropine was injected into VOM,measurement of the refractory period(ERP)of LSPV、LIPV and LAA,Atrial susceptible window(VW).Finally,the ERP and VW of the above sites were measured in the basal state and during the stimulation of LSGP after anhydrous alcohol infusion of VOM.ERP is defined as the longest S1S2 interval during which programmed stimulation does not capture the atrium.ERP shortening value is defined the difference between ERP in basic state and ERP during other nerve stimulation.VW is defined as the difference between the longest S1S2 interval that can cause atrial repetitive response or AF and ERP.Result :(1)Changes in atrial ERP:Before VOM was perfused with anhydrous alcohol,atrial ERP can be significantly shortened by LSGP stimulation(LSPV was1.43±2.45 ms VS 50±5.71 ms,p<0.001;LIPV was 0 ms VS41.43±10.2ms,p<0.001;LAA was 4.29±4.90 ms VS 54.30±9.39 ms,p<0.001).Low-level stimulation of VOM inhibits atrial ERP shortening induced by LSGP stimulation(LSPV was 131.43 ±4.90 ms vs 124.28± 8.98 ms,p=0.09;LIPV was 121.43± 8.16 ms vs 114.29 ±11.84 ms,p=0.09;LAA was 114.3 ± 12.24 ms vs 110.0C14.29 ms,p=0.08).The shortening value of ERP also decreased significantly(LSPV was 32.8 ± 4.88 ms vs7.14±9.51 ms,p<0.001;LIPV was 22.86±7.56 ms vs 7.14±9.51 ms,p=0.03;LAA was 25.7 ±7.87 ms vs 4.23±5.35 ms,p=0.002).The results suggest that low intensity stimulation of VOM can inhibit the shortening of atrial ERP mediated by LSGP.After injection of atropine into VOM under conditions of LSGP stimulation,the ability of atrial ERP shortening was significantly decreased(LSPV was 131.43 ± 4.90 ms vs118.57 ±7.76 ms,p=0.02;LIPV was 121.43±8.16 ms vs 114.29±7.76 ms,p= 0.046;LA A was 114.3±12.24 ms vs 100.0±14.29 ms,p=0.008).The shortening value of ERP was also significantly lower than that of LSGP stimulation alone(LSPV was 32.8±4.88 ms vs 12.85±11.13 ms,p=0.006;LIPV was 22.86±7.56 ms vs 7.14±7.56 ms,p < 0.001;LAA was 25.7±7.87 ms vs 14.29±9.76 ms,p=0.005).The results suggest that the injection of atropine into VOM can partially inhibit the LSGP mediated atrial ERP shortening.After anhydrous alcohol infused with VOM,the ERPs of LSPV and LIPV were unlimited extension,the effect of ERP shortening on LAA induced by LSGP was significantly decreased(LAA was 118.57 ± 10.61 ms vs 111.43 ± 10.20 ms,p >0.05).The ERP shortening of LAA was also significantly reduced(LAA was 25.7±7.87 ms vs 7.14±3.60 ms,p=0.01).The results suggest that ERP shortening induced by LSGP could be significantly decreased by anhydrous alcohol infusion of VOM.(2)Changes of VW in atrium:Before VOM was perfused with anhydrous alcohol,VW was significantly increased by LSGP stimulation(LSPV was 1.43±2.45 ms vs 50±5.71 ms,P < 0.001;LIPV was 0ms VS 41.43±10.2ms,P < 0.001;LAA was 4.29± 4.90 ms vs 54.30 ± 9.39 ms,p< 0.001).That is,AF is easily induced by LSGP stimulation.On the basis of LSGP stimulation with low-level stimulation of VOM,VW of LSGP-mediated decreased markedly(The VW measured by LSPV、LIPV and LAA were 8.57±4.90 ms,p < 0.05;11.43±4.90 ms,p<0.005;11.43±4.90 ms,p<0.05)..On the basis of LSGP stimulation with injection of atropine into VOM,VW of LSGP-mediated decreased markedly(The VW measured by LSPV、LIPV and LAA were17.14±8.98 ms,p=0.01;5.71±6.53 ms,p=0.1;14.29±7.76 ms,p=0.06).The VW was significant differences between LSGP stimulation and low-level stimulation on the basis of LSGP stimulation,LSGP stimulation and injection of atropine into VOM on the basis of LSGP stimulation(P<0.05).It suggested that low-level stimulation of VOM and VOM injection of atropine could inhibit the increasing of VW mediated by LSGP.After anhydrous alcohol was infused in VOM,The increase of VW in basic state and LSGP stimulation were significantly decreased.(LSPV was 0 ms vs 0 ms;LIPV was 0 ms vs 0 ms;LAA was 14.29±7.76 ms vs 18.57±4.90 ms),VW measured by LSGP stimulation before and after anhydrous alcohol infusion in VOM was significantly different(P<0.05).The results suggest that anhydrous alcohol infusion of VOM could inhibit the increase of VW mediated by LSGP.Conclusion:Low-level stimulation and perfusion of atropine could inhibit the shortening of atrial ERP and the increase of AF inducibility mediated by LSGP.Anhydrous alcohol infusion in VOM could prolong atrial ERP and decrease VW.In addition to myocardial injury and local vagotomy in VOM,the mechanism may also be related to the inhibition of LSGP activity. |
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