| Backgroud:Myocardial ischemia reperfusion injury often occurs during the period of restoration of myocardial blood supply after transient ischemia. With the widely use of cardiac extracorporeal circulation, coronary artery bypass grafting, vascular surgical procedures and so on, myocardial ischemia reperfusion injury has become a principal problem of clinical treatment. So far, studys on myocardial preservation have been extensive, including classic ischemia preconditioning, ischemia postconditioning, drugs preconditioning, drugs postconditioning, delayed preconditioning or postconditioning and so on. Morphine, an nonselective opioid receptor agonist, has been widely applied in therapy of anesthesia, analgesia, myocardial infarction and acute left ventricular failure. Further more, being a part of all these preservation method, investigations on Morphine's protection mechanism of myocardial ischemia reperfusion injury have been done deeply and several researchers have found the mechanisms through global or isolated organ and different levels of histiocyte, and confirmed them through ultrastructural organization of cardiac myocyte, infarct size and so on. When myocardial ischemia occurs, segmentally reduced ventricular movements appear meanwhile. However, common two-dimensional echocardiogram can only evaluate the global heart movement efficiently rather than the regional myocardial movement. Strain rate imaging derived from tissue Dopple imaging can evaluate the regional myocardial function accurately during the whole cardiac cycle, especially the systolic and diastolic function of ischemia myocardium by overcoming the drag of surrounding myocardia and interference of global heart movement.Objective:The purpose of the study was utilizing SRI to analyse the change of regional myocardium systolic function within 4 weeks before and after myocardial ischemia reperfusion induced by occlusion and recanalization of coronary artery in New Zealand white rabbits. To investigate the value of non-invasive estimation of regional myocardial function by SRI in myocardial ischemia reperfusion. To evaluation Morphine's attenuation in myocardial ischemia reperfusion injury combining with SRI.Methods:Forty New Zealand white rabbits were divided into sham operated group(n=10), Morphine preconditioning ischemia reperfusion group(n=15) and Normal saline preconditioning ischemia reperfusion group(n=15). All rabbits went with routine echocardiography before the operation and after within 4 weeks(lday,3day,7day,14day,28day after the operation), and dynamic TDI images of left long axis views, four-chamber and two-chamber views were collected at the same time. All of these images were analyzed off-line using TDI software, to survey and statistics analyze TDI parameters including systolic velocity(Vs),systolic strain rate(SRs).Results:1 day after operation, ejection fraction and shortening fraction of left ventricle in morphine preconditionging group and normal saline preconditionging group were lower than preoperative and sham operation group(p<0.05), and they were much more obvious in normal saline preconditionging group(P<0.05).3 day after operation, left ventricular end-diastolic diameter increased in morphine preconditionging group and normal saline preconditionging group compared with preoperative and sham operation group(p<0.05), and they were also much more obvious in normal saline preconditionging group(P<0.05).In basic condition, longitudinal velocity decreased from mitral annulars to apical segment(P<0.05), strain rate did not change(P>0.05); the velocity of left ventricular dissociative wall was higher than that of septum(p<0.05), the strain rate of posterior wall higher than anterior septal, but there's no significant difference(p>0.05).In ischemia reperfusion condition, the Vs has no significant changes in the mitral annulars, basal segments and middle segments of each wall(posterior septal, lateral, anterior, inferior, anterior septal, posterior) in sham operation group within 4 weeks after operation(p>0.05).1 day after operation, the Vs in morphine preconditionging group and normal saline preconditionging group were lower than preoperative and sham operation group in mitral annulars, basal segments and middle segments of anterior wall and anterior septal (P<0.01); as time went after ischemia reperfusion, above-mentioned parameters decreased gradually(p<0.05), and they were decreased obviously in normal saline preconditionging group(P<0.05).In ischemia reperfusion condition, the SRs has no significant changes in the basal segments and middle segments of each wall(posterior septal, lateral, anterior, inferior, anterior septal, posterior) in sham operation group within 4 weeks after operation(P>0.05). 1 day after operation, the SRs in morphine preconditionging group and normal saline preconditionging group were lower than preoperative and sham operation group in basal segments and middle segments of anterior wall and anterior septal (P<0.01); as time went after ischemia reperfusion, above-mentioned parameters decreased gradually(P<0.05), and they were decreased obviously in normal saline preconditionging group(P<0.05).Conclusion:After myocardial ischemia reperfusion, global and regional systolic function of the long axis left ventricular in morphine preconditionging group and normal saline preconditionging group decreased significantly compared with sham operation group, and it is much more obvious in normal saline preconditionging group. Morphine preconditioning attenuate apparently in myocardial ischemia reperfusion injury in rabbits. SRI can detect the variance of regional myocardial function non-invasively, objectively and accurately, and becomes an reliable method of evaluateing myocardial ischemia reperfusion. |
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