| Objective: To evaluate the feasibility of real-time myocardial contrast echocardiographyperforming on models of myocardial ischemic-reperfusion rabbits, and to observe theeffects of ischemic postconditioning on myocardial no-reflow.Methods:60New Zealand white rabbits were randomly divided into Shamoperation(Sham) group, ischemia reperfusion(IR) group and ischemicpostconditioning(IPostC) group, with20rabbits in each group. Sham group： onlythoracotomy without ligation, and suctures were inserted under the left anterior descendingartery(LAD); IR group:LAD occlusion for1h and reperfuseion for2h; IPostC group:fourepisodes of30s reperfusion and30s occlusion after1h ischemia, and before2hours ofreperfusion. ECG monitoring was continuously performed during operation. Andrespectively we record ECG before ligating LAD,10minutes after ligating LAD and2hours after reperfusion. Blood was draw to evaluate serum troponin I, high sensitive C-reactive protein, SOD and MDA before operation,2h after reperfusion and1week after theoperation. Echocardiography and myocardial contrast echocardiography were performedand analyzed1week after the operation. Myocardial infarcted size of rabbits in each groupwas determined by staining with triphyltetrazolium chloride dye(TTC).Morphologicexamination of myocardial tissue was done using optical microscope.Results:1.73New Zealand white rabbits were used, and only60were taken into the experimentalanalysis.There were two died of pneumothorax, and1died of intercostal arterialemorrhage.Death rates were2.74%and1.37%respectively.there was no infection ordeath after the operation.2. There is no difference in age,body weight and sex between each group (P>0.05). 3. The heart rate slightly accelerated after ligation,but there was no difference comparedwith pre-operation(P>0.05). The level of ST-segment rise ten minutes after ligation wassimilar between IPostC and IR group(3.59±0.63mm vs3.75±0.72mm, P>0.05).TheST-segment resolutions ten minutes after reperfusion were signigicantly decreased inIPostC group compared with IR group (1.64±0.84mm vs2.95±0.76mm P<0.05).4.3h after ligation, the value of cTnI was similar between IPostC group and IRgroup(2.03±0.25ng/ml vs2.17±0.33ng/ml，P>0.05). the value of hsCRP and MDA ofIR group was higher than IPostC group,and the value of SOD waslower(7.94±1.20μg/ml vs4.55±0.90μg/ml，2.46±0.58μmol/ml vs0.94±0.34μmol/ml,17.13±5.75ng/ml vs40.87±9.93ng/ml，P<0.05). One week after the ligation,the valueof cTnI and MDA of IR group was higher than IPostC group,and the value of SOD waslower(1.65±0.25ng/ml vs1.09±0.17ng/ml，2.52±0.57μmol/ml vs1.02±0.28μmol/ml，16.50±5.89ng/ml vs40.58±9.16ng/ml，P<0.05). There was no significant difference inthe value of hsCRP(0.78±0.17μg/ml vs0.74±0.11μg/ml，P>0.05).5. There was no significant difference between IR and IPostC group in LVEDD、LVESDand LVEF measured by echocardiography performed1w after the operation(18.6±5.2mm vs17.4±3.8mm，13.1±2.4mm vs12.6±5.1mm，59.5±7.9%vs62.4±8.2%，P>0.05).6. During the operation of myocardial contrast echocardiography, there was no adversereaction on rabbits.there was no significant difference in heart rate and ST-segmentbefore and after the operation.7. Quantitative analysis by myocardial contrast echocardiography:The A value,β valueand A×β value between six segments in Sham group had no significant difference(P<0.05). Low perfusion was observed in the front wall, lateral wall and anteriorseptal. The A value,β value and A×β value in these segments were lower than posteriorwall, inferior wall and posterior septum in IR group (P<0.05). In IPostC group, The Avalue and A×β value were lower (P<0.05),and the β value was not. The A value,β valueand A×β value between Sham and IR group and between IR and IPostC group were significant different (P<0.05). The A value and A×β value had significant differencebetween Sham group and IPostC group (P<0.05), but the β value was not (P>0.05).8. The areas of myocardial infarction by TTC staining were observed in the front wall,lateral wall and anterior septal. Infarction area of IPostC group was less than IR groupwith significant differences (7.72±1.63%vs22.0±3.42%，P<0.05).9. Morphologic examination indicated that there were milder injuries of thecardiomyocyte of rabbits in IPostC group compared with IR group. No thrombus orcontrast agent was observed in the capillaries of three groups.Conclusions:1. The method of “four sutures and four knots” allying with dividing sternocostal jointcould successfully reduce intercostal arterial hemorrhage and pneumothorax formation,and was helpful to keep the normal shape of thorax and reduce postoperativecomplications.2. Myocardial contrast echocardiography(MCE) examination is a real-time andnon-invasive method evaluating microcirculation and can be quantified. This studyfound that MCE could be performed safely and accurately on models of myocardialischemic-reperfusion rabbits.3. Ischemic postconditioning could obviously reduce myocardial reperfusion injury,restrain release of inflammatory factors and reduce aeras of myocardial infarctions.4. It was found by using the method of real-time myocardial contrast echocardiographyexamination that ischemic postconditioning was conductive to maintaining myocardialblood volume and blood flow velocity and thus was helpful to improve the myocardialmicrocirculation.But the current research results are controversial, it is worth furtherdiscussion. |
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