| Part one Effects of coronary vein peripheral sympathetic denervation on ventricular electrophysiological properties in normal heartObjective: Observed effects of local radiofrequency denervation on left ventricular electrophysiological properties in normal dogs. Stimulate the left stellate ganglion of dogs, observed the influence of local sympathetic denervation on Cardiac sympathetic nerve system.Methods: 16 mongrel dogs were randomly assigned into the ablation group(n = 8) and the sham-operated group(n = 8). In ablation group, the irrigated radiofrequency catheter tip was placed on the left ventricular, which was only 2 mm away from LAD artery. Current was delivered from the LAD artery bifurcation to the apex.Catheter tip impedance and temperature were constantly monitored. In sham-operated group, the catheter tip were placed on the same position but without application of ablation energy. Isolated and exposed the left stellate ganglion, stimulated the left stellate ganglion, then measured systolic blood pressure, heart rate, recording the surface ECG. The ventricular effective refractory period(ERP) and the monophasic action potential duration(MAPD) were determined with the programmed ventricular stimulation during baseline sinus rhythm and 1h after local radiofrequency denervation and during left stellate ganglion stimulation. Pathological examination of the ablation area to confirm if there is any destroy on vascular and sympathetic fibers. Results were shown by x ± s, ERP and MAPD90 changes were tested by paired t test. p<0.05 was considered significance. All statistical analyzes were applyed by SPSS 21.0 software.Results: 1. Pathology showed no injury in ablation group and sham-group. TH staining in ablation group showed the sympathetic nerve fibers damage at the ablation area; 2. ERP values in ablation group were significantly prolonged after ablation(174.2±8.8ms vs. 163.5±8.1ms,p<0.05), sham group was observed inconsistencies(164±7.4ms vs. 163.1±7.8ms,p>0.05); 3. ERP dispersion in ablation groups and sham group showed no difference after ablation compared with the baseline(0.028±0.003 vs.0.021±0.005,p>0.05); 4. ERP values in ablation group and sham group were significantly shorter in response to left stellate ganglion stimulation(142.2±4.9ms vs. 163.1±7.8ms,p<0.01;170.8±7.9ms vs. 174.2±8.1ms,p<0.05). ERP shorten-values in ablation group was significantly lower than the sham group,(2.5 ± 2.5ms vs 21 ± 5.2ms, p <0.05); 5. MAPD90 values in ablation group were significantly prolonged compared with the previous measurement before ablation(235.7±13.8ms vs. 213.7±9.7ms,p<0.05). The sham group was not observed significant change after false-ablation.(214.4±6.9ms vs. 216.4±8.6ms,p>0.05); 6. Both groups showed increased systolic blood pressure after stimulation of the left sympathetic ganglion(162±13mm Hg vs. 141±13 mm Hg, p<0.01; 149±15 mm Hg vs. 146±14 mm Hg, p<0.05); No significant change in heart rate in both groups. The systolic blood pressure of ablation group was significantly lower than that of the sham operation group(149±15 mm Hg vs. 162±13mm Hg, p<0.01); 7. TH staining showed that the density of sympathetic nerve fibers in the ablation group was significantly less than that in the sham-operated group(482.97±173.9 vs. 1416.02±336.06,p<0.05).Conclusion: 1. Coronary vein peripheral sympathetic denervation was safe and effective, which could partially damage the left ventricular sympathetic nerve; 2. Local sympathetic denervation can extend left ventricular ERP and MAPD. Radiofrequency ablation does not affect left ventricular refractory period dispersion; 3. Radiofrequency ablation could partially inhibit the positive inotropic caused by left sympathetic ganglion stimulation.Part Two Effects of coronary vein peripheral sympathetic denervation on sympathetic and electrophysiological properties in myocardial infarction dogsObjective: Observed effects of local radiofrequency denervation in myocardial infarction dogs on sympathetic and electrophysiological properties. Investigate its influence on ventricular arrhythmia after myocardial infarction.Methods: 18 mongrel dogs were randomly divided into the ablation group(ablation+AMI, n=9) and the control group(AMI, n=9). In ablation group, the irrigated radiofrequency catheter tip was placed on the left ventricular, 2 mm away from LAD artery. Current was delivered from the LAD artery bifurcation to the apex. The animals in control group were also undergoing thoracotomy and pericardiotomy, Catheter tip were placed on the same position without application of ablation energy. An hour after local denervation or sham treatment, the first diagonal artery was isolated in both group, then occluded by ligature(3-0 silk) for half hour until the ischemic part turned dark red to make sure that the ligation was successful. Norepinephrine levels and the ERP values were measured. The incidence of VA was recorded in these two groups. Results were shown by x± s,NE changes were test by independent-samples T test. ERP and MAPD90 changes were tested by paired t test, to compare the incidence of VF between groups, Fisher’s exact test was used. p<0.05 was considered significance. All statistical analyzes were applyed by SPSS 21.0 software.Results: 1. Half hour after AMI, a significant decrease of MAPD90 from the infarct zone was shown in the control group(197±6.7ms vs. 214.4±6.9ms, P<0.05) but no change in ablation group(215.7±5.3ms vs. 213.4±9.6ms,p>0.05); 2. The MAPD90 from the remote area was not changed during AMI in both groups(217.2±8.3ms vs. 214.4±10.3ms;229.1±8.8ms vs. 234.4±10.8ms,p>0.05) and kept at a level almost same to that before AMI; 3. ERP values in both groups were significantly shorter compared with the measurement results before ligation(156.9±11.4ms vs 143.8±10.8ms; 175±13 ms vs 165.3±14.8ms, p<0.05); Both groups all showed different shortness of ERP among different areas, especially on the infarct area(p<0.05);4. ERP shorten-values in ablation group was significantly lower than the control group(17.4±7.1ms vs 31.9±9.4ms, p<0.05); 5. Both groups showed increased ERP dispersion after AMI compared to baseline(p<0.05); ERP dispersion in ablation group was significantly lower than the control group(0.0364±0.015 vs 0.0734±0.0177, p<0.05); 6. NE concentrations in control group were significantly higher compared with the previous(199.1±25.9 ng/L vs. 576.9±78.5 ng/L; p<0.05), they were also higher than the ablation group(196.5±20.8 ng/L vs. 292.1±59.8 ng/L, p <0.05); Changes in the ablation group was increase less than the control group; 7. The number of PVC in the ablation group was significantly decreased compared with the control group(51±35.4 vs. 117.6±56.1,p<0.05); Moreover, the number of VT episodes and the duration of VT were significantly decreased in the ablation group compared with the control group(6±2.4 vs. 2.1±0.6,1.6±0.6s vs. 2.7±1s, p<0.05); Spontaneous VF occurred in 33%(3/9) of all control animals during LAD occlusion. By contrast, 11%(1/9) of all ablation animals during LAD occlusion experienced spontaneous VF(P<0.05).Conclusion: 1. Coronary vein peripheral sympathetic denervation can decrease sympathetic nerve activity, significantly prolonged ventricular APD after acute myocardial infarction. 2. Radiofrequency ablation can extend left ventricular ERP, especially in the ischemia area. ERP dispersion was progressively decreasing after ablation. 3. Radiofrequency ablation can reduce the catecholamine concentrations and prevented the incidence of AMI-induced VAs, improve ventricular electrical stability after AMI.Part Three Effects of coronary vein peripheral sympathetic denervation on cardiac sympathetic remolding and its correlation with arrhythmia after myocardial infarctionObjective: Observed effects of local radiofrequency denervation on sympathetic innervation and myocardial repolarization after myocardial infarction.Methods: 12 mongrel dogs were randomly divided into the MI group(n = 4), the ablation group(n = 4) and control group(n = 4). In ablation group, Ablation of cardiac sympathetic was also conducted. An hour after local denervation or sham treatment, the first diagonal artery was isolated in MI group and ablation group, then occluded by ligature(3-0 silk) for half an hour until the ischemic part turned dark red to make sure that the ligation was successful. The ERP of the no infarcted myocardium apical and basal to the infarction were determined with the programmed ventricular stimulation during baseline sinus rhythm and left sympathetic ganglion stimulation and under high-dose norepinephrine 4 weeks after infarction. ventricular fibrillation threshold(VFT) were measured during the experiments. Immunohistochemical technique was carried out in the regions where electrode sites located to identified cardiac sympathetic nerve. Results were shown by x± s, ERP values were tested by paired t test. p<0.05 was considered significance. All statistical analyzes were applyed by SPSS 21.0 software.Results: 1. ERP in both the apical and basal regions to the infarction were same in all three groups.(162.5±9.4ms vs. 164±10.8ms;161.5±12.6ms vs. 157.8±12.8ms;165.5±10.3ms vs. 160±9.9ms,p>0.05); 2. Shortening of ERP values in response to left stellate ganglion stimulation was present at both regions in control group(142.3±7.9 ms vs. 162.5±9.4 ms;143.8±5.8ms vs. 164±10.8ms;p<0.05); During the infusion of norepinephrine, basal and apical ERPs shortened in control group(147±8.6 ms vs. 162.5±9.4 ms;148.8±6.2ms vs. 164±10.8ms;p<0.05); 3. In MI group, the ERP of the non-infarcted myocardium at the base of heart proximal to the infracted myocardium was significantly shortened after stimulation on left stellate ganglion(139.8±9.1ms vs. 161.5±12.6,p<0.05); The ERP of the non-infarcted myocardium at the apex of heart has no significantly change after stellate ganglion stimulation.(154 ± 14.4ms vs. 157.8 ± 12.8ms, p>0.05); However, the apical ERP shortened significantly more than did basal ERP in MI group after the infusion of norepinephrine.(137.3±14.8ms vs. 122.8±9.8ms,p<0.05); 4. The ERP values of the both regions were no significantly different from that before stellate ganglion stimulation in ablation group.(165.5±10.3ms vs. 164.8±6.8 ms;160±9.9ms vs. 163.2±12.3ms;p>0.05); During the infusion of norepinephrine, ERP values at basal and apical sites shortened in ablation group(123±10.7 ms vs. 165.5±10.3ms;122.3±8.3ms vs. 164.8±6.8ms;p<0.05). And the degree of shortening at apical and basal sites was equivalent(123±10.7ms vs. 122.3±8.3ms,p>0.05); 5. In comparison with the MI group, the VFT in the ablation group significantly decreased(12±2.4 vs. 16.2±2.1,p<0.05). 6. Immunohistochemistry showed extensive denervation in the region below the infarct, but sympathetic nerve fibers were retained in the base of heart in the MI group(2229.02±316.04 vs. 580.55±105.65,p<0.05). The whole areas in the ablation group showed extensive denervation(527.01±248.14 vs. 472.89±420.16,p>0.05).Conclusion: 1. Coronary vein peripheral sympathetic denervation can decrease sympathetic nerve activity, significantly prolonged ventricular APD after AMI. 2. Radiofrequency ablation can extend left ventricular ERP, especially in the ischemia area. ERP dispersion was progressively decreasing after ablation. 3. Radiofrequency ablation can reduce the catecholamine concentrations and the incidence of AMI-induced VAs, improve ventricular electrical stability after AMI. |
PDF Full Text Request