| Part One Spinal cord stimulation induce changes in compound actionpotentials of cardiac sympathetic nerves and cardiac function in rabbitswith heart failure after acute myocardial infarctionObjective: This study sought to evaluate the effect of different electricalfrequency of spinal cord stimulation(SCS) on cardiac sympathetic nerveregulation and cardiac function in rabbits with heart failure (HF) after acutemyocardial infarction(AMI), in order to explore theoretical mechanism andevidence based medicine for next clinical trials.Methods:40New Zealand white rabbits weighing2.5-3.0Kg wereselected for left anterior descending artery ligation for the induction of HFafter AMI. Another20age-and weight-matched health New Zealand whiterabbits with normal electrocardiogram and without AMI were used as controls.Detailed echocardiography was performed to measure cardiac function beforeand after4weekend and different frequency of SCS separately, the compoundaction potentials of cardiac sympathetic nerves and cardiac function wasestimated before and after SCS. After completed all SCS and removed theheart, recorded infarct location and calculated infarct size.Results: After SCS treatment, there were no significant differences inthe maximum stimulus intensity(82.31±14.16VS.100.57±12.14μv，P=0.733) and amplitude（158.49±3.51VS.201.22±10.35ms，P=0.687） of compoundcardiac action potentials before and after stimulation(5HZ) in HF group;However, there had significant differences in the maximum stimulusintensity(48.32±7.58μv) and amplitude (116.65±3.47ms) of compoundcardiac action potentials in stimulus frequency (50HZ) as compared withstimulation(5HZ) and stimulation before(P＜0.05). Moreover, there hadsignificant differences in the maximum stimulus intensity(57.32±7.55μv)and amplitude (127.21±2.69ms) of compound cardiac action potentials instimulus frequency (500HZ) as compared with stimulation(5HZ) andstimulation before either(P＜0.01). the maximum stimulus intensityand amplitude of compound cardiac action potentials in stimulus frequency(500HZ) was lower than in stimulus frequency (50HZ)(P＜0.01). Meanwhile,the whole heart weight (189.35±17.64VS.143.17±13.26mg, P=0.033),ventricular weight (104.57±8.63VS.73.35±11.03mg,P=0.029) in HF groupwas higher than controls. In comparisons of cardiac function parameters,LVEDD(5HZ:16.39±2.63mm VS.19.11±2.96, P=0.147,50HZ:12.53±2.36VS.19.11±2.96, P=0.034,500HZ:14.33±1.61VS.19.11±2.96, P=0.041),LVESD(5HZ:12.11±1.3VS.13.18±3.14, P=0.419,50HZ:9.6±2.77VS.13.18±3.11, P=0.024,500HZ:10.96±2.14VS.13.18±3.11, P=0.039) and E/A(5HZ:2.42±1.68VS.2.87±1.13, P=0.473,50HZ:1.67±0.72VS.2.87±1.13,P=0.021,500HZ:1.67±0.72, P=0.039)had lower than before SCS. However,EF（5HZ:0.59±0.02VS.0.51±0.03,P=0.428,50HZ：0.71±0.04VS.0.51±0.03,P=0.014，500HZ：0.65±0.03VS.0.51±0.03, P=0.025），Evelocity(5HZ:73.56±3.11VS.72.35±2.63cm/s, P=0.223,50HZ:81.56±1.19VS.72.35±2.63cm/s, P=0.018,500HZ:79.53±2.34VS.72.35±2.63cm/s, P=0.021) and Avelocity (5HZ:27.49±1.39VS.24.19±2.67, P=0.369,50HZ:40.37±3.3 VS.24.19±2.67cm/s, P<0.01,500HZ,34.42±1.57VS.24.19±2.67cm/s，P=0.041）had higher in HF group compared with before SCS.Conclusions: In rabbit model of ischemic HF, the compound actionpotentials of cardiac sympathetic nerves decreased and LV contractilefunction improved by the medium-high frequency of SCS. Part two Regulation of spinal cord stimulation on serum brainnatriuretic peptide,cTnT and CK-MB in rabbits with heart failure afteracute myocardial infarctionObjective: To investigate SCS triggers the content changes of serumbrain natriuretic peptide (B-type natriuretic peptide, BNP), cardiac troponin(cardiac troponin T, cTnT) and myocardial creatine kinase (MB isoenzyme ofcreatine kinase, CK-MB) in rabbits with HF after AMI.Methods:40New Zealand white rabbits weighing2.5-3.0Kg wereselected for left anterior descending artery ligation for the induction of HFafter AMI. Another20age-and weight-matched health rabbits with normalelectrocardiogram and without AMI were used as controls. Detailedechocardiography was performed to measure cardiac function and myocardialenzymes examination in4weekends, before and after SCS. Drawed venousblood from rabbit ears before and after established HF model and before andafter SCS in HF group and controls, analyzed the content changes ofBNP, cTnT and CK-MB. Results: Compared with the control group, the levels of BNP, cTnT andCK-MB significantly increased in HF group(BNP:324.63±9.86VS.54.68±6.51ng/ml,P=0.006, cTnT:2.18±1.36VS.0.34±1.06ng/ml, P=0.028,CK-MB:7.18±3.36VS.3.23±0.41, P=0.031). After SCS, the levels of BNPincreased compared with SCS before (56.35±6.14VS.324.63±9.86ng/ml,P=0.004) in HF group. However, there were no significant differences in thecontent of cTnT and CK-MB before and after SCS(P＞0.05)..Conclusion: SCS can decrease sympathetic nerve activity, reduced thelevels of BNP, improved the cardiac function, SCS may reduce myocardialinjury as a new treatment for heart failure. |
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