| Objective: The incidence of ventricular arrhythmia(VA)is higher in patients with acute myocardial infarction(AMI)patients.Sympathetic overactivation and sympathetic remodeling are important mechanisms for the development and maintenance of VA after MI.However,electrical stimulation of the vagus nerve branch can reduce the incidence of ventricular arrhythmia in the AMI model.Methods and Results: Fourteen healthy adult dogs were anesthetized and ligated the anterior descending branch of coronary artery to establish the MI model.A successful model of MI dogs were randomly divided into two groups: AB-VNS group(auricular stimulation group,n=7)and control group(with no stimulation,n=7).The electrical stimulation of AB-VNS group(80% threshold voltage,20 Hz,1-ms pulse width,square wave)was applied to the left or right ear for 1h every other day a total of 30 days;The control group was not given any stimulation;We have monitored spontaneous ventricular arrhythmias at basic level,30 min post MI and 4weeks post-stimulus,respectively.The effective refractory period(ERP)of different sites of the two groups at different sites and different time periods were monitored separately.The MAP90 of both groups was also monitored and the slope of the MAP90 recovery curve was calculated.After the completion of the electrophysiological examination,Tyrosinehydroxylase(TH)and Choline acetyltransferase(Chat)staining of myocardium and nerve tissue was performed to evaluate the positive expression of nerve.The vagus nerve(ABVN)fiber ear branch is given Hematoxylin-Eosin(HE)staining.The structure and morphological changes of nerve tissue are evaluated by HE staining and ultrastructural.In addition,TTC staining was used to assess the area of myocardial infarction,and RT-PCR was used to assess receptor expression and distribution of autonomic nerves.Results-Compared with the control group,the incidence of all types of ventricular arrhythmia in the AB-VNS group was significantly lower(P<0.05).After 4 weeks of vagus nerve stimulation,the ERP of the endocardial and epicardial membrane of the AB-VNS group increased significantly,and the dERP decreased compared with the control group.The difference was statistically significant.No difference was found between two groups in MAPD90.The maximum slope of the MAP90 recovery curve was: AB-VNS<control group(1.27 vs 1.78).The results of tissue staining showed that the number of Chat-positive nerve fibers in the LV of the AB-VNS group was decreased than the control group,whereas the positive expression in the vagus nerve was increased.Compared with the control group,the TH-positive nerve fibers of the LV and sympathetic nerves in the AB-VNS group were reduced.Ultrastructure: In the AB-VNS group,the mitochondria in the axons of the neurons were slightly swollen under visual conditions.TTC staining showed a significant decrease in myocardial infarction area after 4 weeks of vagus nerve stimulation.RT-PCR: The expression of CHRNA7 in the AB-VNs group increased after vagus nerve stimulation;the beta1 and beta3 in the MI region of the AB-VNS group were higher than those in the control group;the beta1 and beta3 in the non-infarcted AB-VNs group were lower than the control group.Conclusions: Percutaneous vagus nerve stimulation can reduce the electrical remodeling and nerve remodeling of the heart after myocardial infarction.Increase the electrical stability,improve the abnormal distribution of the heart after myocardial infarction,reduce the structural remodeling of the heart and further prevent the occurrence of ventricular arrhythmia,thus it will play a protective role to the myocardium after acute myocardial infarction.Therefore,non-invasive stimulation may be a new treatment. |
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