Radiofrequency Ablation Of Cardiac Vagus Ganglia Attenuate Bezold-Jarisch Reflex And It's Effect On Cardiac Electrophysiological Characteristic In Dogs

Background:The Bezold-Jarisch reflex(B JR) is a cardiovascular inhibitory reflex, which means cardiac receptors stimulated,excitation is conducted to the solitary tract nucleus of the brain stem and rostral ventrolateral medulla nuclear by the non-myelinated vagus nerve fibers,causing the increases of parasympathetic output activity,the decreases of sympathetic output activity and the secretion of renin and antidiuretic hormone, ultimately lead to the decrease of heart rate and arterial blood pressure.BJR is consided one of the main triggering mechanisms of vasovagal syncope(VVS).Block or reduce vagus nerve activity may contribute to the prevention of VVS.Vagal postganglionic neurons to the sinus node are mainly located in a fat pad adjacent to the right pulmonary vein-atrial junction(RPV fat pad),while the vagal postganglionic neurons to the AV node are mainly located in a fat pad at the junction of the inferior vena cava and left atria(IVC-LA fat pad).The postganglionic neurons in the fat pad located between the superior vena cava and aortic root(SVC-Ao fat pad) are the head stations of vagal fibers traveling to the sinus node,the AV node and atria.Destruction of the vagus ganglia and fibers in the fat pads above mentioned could attenuate the negative chronotropic,inotropic and dromotropic effects caused by BJR.PartⅠBuilding Bezold-Jarisch reflex model by injecting veratridine into the left ventricle in dogsObjective:To observe the Bezold-Jarisch reflex(BJR) induced by injecting different doses of veratridine into the left ventricle and build Bezold-Jarisch reflex model in dogs.Methods:Seven mongrel dogs were anesthetized and a cardiac catheter was inserted from the left carotid artery to the left ventricle.Veratridine was injected into the left ventricle in bolus doses of 5μg/kg,10μg/kg,15μg/kg and 20μg/kg in sequence through the cardiac catheter to induce BJR.Changes of heart rate(HR),mean arterial pressure(MAP) were observed.The basic values of them before injection,the minimum values of them after injection and the maximum decrements of them which were indicated withΔHR andΔMAP were measured.When HR and MAP recovered to the basic values after the former dose had been injected and maintained at this level for more than 15 minutes,the latter dose of veratridine was injected.The relationship between the doses of veratridine and the percentage ofΔHR andΔMAP was observed.The standard of canine BJR model was defined as that the percentage ofΔHR andΔMAP should exceed 50%.Results:The temporary decrease of HR and MAP was observed after injecting each dose of veratridines in all dogs.The minimum value of HR and MAP which was causes by the four doses of veratridine was significantly smaller than the basic value(P<0.01). The correlation between the dose of veratridine and the minimum value of HR after injecting veratridine was negative,while the correlation between the dose of veratridine andΔHR was positive.The differences between the minimum values of HR which caused by the adjacent doses of veratidine have statistical significance(P<0.05),the percentage ofΔHR was the same(P<0.05).The correlation between the dose of veratridine and the minimum value of MAP after injecting veratridine was negative. Comparing the differences between the minimum values of MAP which caused by the adjacent doses of veratidine,only the values between the does of 10μg/kg and 5μg/kg have statistical significance(P<0.05).The correlation between the dose of veratridine andΔMAP was positive.Comparing the differences between the percentage ofΔMAP which caused by the adjacent doses of veratidine,only the values between the does of 10μg/kg and 5μg/kg,the values between the does of 15μg/kg and 10μg/kg have statistical significance(P<0.05).The percentage ofΔHR andΔMAP which was caused by veratridine at the doses of 15μg/kg and 20μg/kg exceeded 50%.The two above-mentioned doses could be regarded as the doses to build the BJR model in dogs.Conclusion:BJR can be successfully induced by injecting veratridine into the left ventricle in dogs.This model is built conveniently and reliably.PartⅡRadiofrequency ablation of cardiac vagus ganglia attenuate Bezold- Jarisch reflex in dogsObjective:To observe the influences of radiofrequency ablation of vagus ganglia in the three fat pads(RPV,IVC-LA,and SVC-AO fat pads) on the BJR and left ventricular function.Methods:Sixty mongrel healthy dogs were randomly divided into four groups,each group have fifteen dogs.All dogs were anesthetized by 3%pentobarbital sodium intravenously,ventilated with room air by use of a cuffed endotracheal tube and a respirator.A sheathing canal was placed in the left femoral artery and connected to a transducer to monitor arterial blood pressure.Another sheathing canal was placed in the left carotid artery,then a cardiac catheter was inserted from the sheathing canal to the left ventricle to monitor left ventricular pressure.ECG monitor was also performed.After the chest was opened through a right sternotomy,the pericardium was opened and sewn to the chest wall to cradle the heart.The three fat pads above mentioned were exposed. Dogs in control group were not accepted radiofrequency ablation.Dogs in epicardial ablation group 1 were accepted ablation of RPV and IVC-LA fat pads epicardially,while dogs in epicardial ablation group 2 were accepted ablation of RPV,IVC-LA and SVC-AO fat pads epicardially.Dogs in endocardial ablation group were accepted ablation of RPV and IVC-LA fat pads endocardially.Heart rate(HR),systolic arterial pressure(SAP),diastolic arterial pressure(DAP),mean arterial pressure(MAP),left ventricle systolic pressure(LVSP),left ventricle end-diastolic pressure(LVEDP),left ventricular peak systolic and diastolic velocity(±dp/dt_max)were measured before and after injecting veratridine in bolus doses of 15μg/kg through the left ventricular catheter.The fat pads were performed HE staining after above experiment. Results:The basic values of HR,SAP,DAP,MAP,LVSP,LVEDP,+dp/dt_max and -dp/dt_max in each group had no significant difference(P>0.05).After injecting veratridine in bolus doses of 15μg/kg,all the indexes appeared temporary decrease except LVEDP, the minimum values of them were significantly lower than the basic values(P<0.01).The minimum value of HR in the three ablation groups were significantly higher than of the control group(P<0.01).The value of AHR and the percentages ofΔHR in the three ablation groups were significantly lower than of the control group(P<0.01).There was no difference in the value ofΔHR and the percentages ofΔHR among the three ablation groups(P>0.05).ΔSAP,ΔDAP,ΔMAP,ΔLVSP,Δ+dp/dt_max andΔ-dp/dt_max had no difference among the four groups(P> 0.05).In the fat pad before ablation,the membranes of vagus ganglia were intact,the postganglionic neuron cells were full and the arrange was compact,the nerve fibers were abundant.In the fat pad after ablation,fatty tissues appeared necrosis,the membrane of vagus ganglia were destroyed,the postganglionic neuron cells appeared shrinkage,the nerve fibers reduced and were deranged.Conclusions:1.Radiofrequency ablation of canine vagus ganglia in RPV and IVC-LA fat pads epicardially can significantly attenuate the decrease of heart rate of BJR which induced by veratridine,but it can not attenuate the decrease of arterial pressure, the pressure and the contractility of left ventricle.On this ablation base,adding ablation of SVC-AO fat pad has no additional effect on the BJR.2.Radiofrequency ablation of canine vagus ganglia in RPV and IVC-LA fat pads endocardially can also significantly attenuate the decrease of heart rate of BJR which induced by veratridine.This effect has no difference with the effect of ablation of RPV and IVC-LA fat pads epicardially.But it can not attenuate the decrease of arterial pressure,the pressure and the contractility of left ventricle also.This method may be useful in the prevention of cardio-inhibitory type of VVS but invalid in the prevention of vascular-inhibitory type of VVS.PartⅢRadiofrequency ablation of cardiac vagus ganglia affect cardiac electrophysiological characteristic in dogs Objective:To estimate the function of sinoatrial node and atrioventricular node, atrial effective refractory period(AERP) before and after radiofrequency ablation of vagus ganglia in the three fat pads(RPV,IVC-LA,and SVC-AO fat pads) on the baseline and the truncus vagosympathicus stimulation state.Methods:Fourty five mongrel healthy dogs were randomly divided into three groups,each group have fifteen dogs.All dogs were anesthetized by 3%pentobarbital sodium intravenously,ventilated with room air by use of a cuffed endotracheal tube and a respirator.The left and right vagus truncus vagosympathicus in the neck were exposed.After the chest was opened through a right sternotomy,the pericardium was opened and sewn to the chest wall to cradle the heart.The three fat pads above mentioned were exposed. Dogs in epicardial ablation group 1 were accepted ablation of RPV and IVC-LA fat pads epicardially,while dogs in epicardial ablation group 2 were accepted ablation of RPV, IVC-LA and SVC-AO fat pads epicardially.Dogs in endocardial ablation group were accepted ablation of RPV and IVC-LA fat pads endocardially.Sinoatrial node recovery time(SNRT),sinus node recovery time correction(CSNRT),sinoatrial node conduction time(SACT),atrioventricular nodal anterior Wenckebach cycle length(WCL) and atrial effective refractory period(AERP) were measured in the dogs of three ablation groups before and after ablation.Results:1.On the baseline,compared with the values of SNRT,CSNRT,SACT and atrioventricular nodal WCL before ablation,the values after ablation had no difference in the three groups(P>0.05).There were also no difference among the three ablation groups(P>0.05).AERP of epicardial ablation group 2 after ablation was longer than of before ablation(P<0.05),while AERP of the other two ablation groups before and after ablation had no significant difference(P>0.05).2.On the truncus vagosympathicus stimulation state,the values of SNRT,CSNRT,SACT and atrioventricular nodal anterior WCL after ablation were shorter than of before ablation in the three groups(P<0.05). There were also no difference among the three ablation groups(P>0.05).AERP of epicardial ablation group 2 after ablation was longer than of before ablation(P<0.05), while AERP of the other two ablation groups before and after ablation had no significant difference(P>0.05).Conclusions:Radiofrequency ablation of canine vagus ganglia in RPV and IVC-LA fat pad or combinating ablation of vagus ganglia in SVC-AO fat pad have no significantly effect on the sinus node function and the atrioventricular nodal function on baseline,but it can improve the sinus node function and the atrioventricular nodal function on the truncus vagosympathicus stimulation state.Radiofrequency ablation of canine vagus ganglia in RPV and IVC-LA fat pad had no significantly effect on AERP. Combinating ablation of vagus ganglia in SVC-AO fat pad can extend AERP.