二维应变超声心动图评价大鼠急性心肌梗死模型局部心肌功能改变的应用价值

目的 探讨二维应变超声心动图定量评价大鼠急性心肌梗死模型左室局部心肌功能改变的应用价值.方法 60只Wistar大鼠随机分为两组:实验组50只,制备急性冠状动脉心肌梗死模型;假手术组10只.两组分别于术前及术后1周、4周、8周行超声心动图检查.解剖M型超声心动图测量左室舒张末期及收缩末期内径(LVIDd、LVIDs)、短轴缩短率(FS)、射血分数(EF)和左室质量(LVM).记录左室乳头肌短轴高帧频图像,应用二维应变分析软件测量各节段的收缩期峰值径向应变(PRS)、环向应变(PCS).实验组大鼠检查结束后处死,取出心脏行TTC染色并计算梗死面积;VG染色观察心肌组织中的胶原纤维.结果 根据TTC染色结果将实验组大鼠左窀分为梗死心肌、梗死周围和远处心肌.术后1周VG染色显示实验组大鼠左室各节段均出现不同程度的胶原纤维沉着.与术前及同时期假手术组相比,实验组大鼠于术后1周时梗死心肌、梗死周围及远处心肌的PRS、PCS均明显降低(P<0.01),并持续至第8周.与术后1周时相比,术后4周、8周实验组大鼠梗死心肌、梗死周围及远处心肌的PRS、PCS差异无统计学意义.实验组大鼠于术后4周和8周LVIDd、LVIDs及LVM明显增加,FS明显减低(P<0.05).二维应变测量组间及组内比较均具有高度一致性.结论 二维应变超声心动图可定量评价大鼠心肌梗死模型不同血供区域局部心肌的功能改变,为无创性跟踪心肌梗死后左室重构进程提供了一种敏感可行的方法.

Assessment of left ventricular regional myocardial function after acute occlusion of the left anterior descending artery in rats model by two-dimensional strain echocardiography

Objective To explore the value of two-dimensional strain echocardiography for quantitative assessing the change of regional left ventricular myocardial function in rats following acute myocardial infarction. Methods Sixty Wistar rats were randomly divided into two groups. The study group consisted of 50 rats with occlusion of LAD for 30-45 minutes and the sham-operated group consisted of 10 rats without occlusion of LAD. Echocardiography were performed before operation, which was defined as baseline, and 1 week, 4 weeks and 8 weeks after operation. Left ventricular internal diameter at diastole ( LVIDd) and systole < LVIDs), fractional shortening( FS), ejection fraction (EF) and left ventricular mass(LVM) were measured by anatomical M-model echocardiography. High frame rate two-dimensional images were recorded in the left ventricular short-axis views at the papillary muscle level. Peak systolic radial strain(PRS) and circumferential strain(PCS) of each segment were measured using 2-dimensional strain software. The rats were sacrificed and the infarcted size of each segment was measured using triphenyl tetrazolium chloride (TTC) after echocardiography was performed. Fibrosis of left ventricular myocardium was displayed using Van Gieson stain in 1 weeks after infarction. Results Based on the TTC findings,the left ventricle of the study group was divided into three regions:infarcted,peri-infarct and remote myocardial regions. Van Gieson stain showed fibrosis existed in all the three regions. Compared with baseline and sham-operated group, PRS and PCS of infarcted, peri-infarct and remote myocardial regions of the study group significantly decreased within 1 week after operation ( P <0. 01) and persisted for 8 weeks. PCS and PRS of infarcted, peri-infarct and remote myocardial regions of the study group in 4 weeks and 8 weeks after operation showed no significant difference when compared with those in 1 week after operation ( P >0. 01). Compared with baseline and sham-operated group,LVIDd,LVIDs and LVM of study group all increased significantly ( P <0. 05) in 4 weeks and 8 weeks after operation,and FS and EF reduced significantly ( P <0. 05). Two-dimensional strain obtained in interobserver and intraobserver both showed high agreement. Conclusions Two-dimensional strain echocardiography can assess regional function of myocardium with different perfusion in rats following acute myocardial infarction, and provides a sensitive and reliable method to follow up the process of left ventricular remodeling after myocardial infarction.