二维超声斑点追踪成像评估大鼠不同程度心肌损伤的应用价值

目的 探讨基于二维超声斑点追踪成像(2D-STI)技术的左心室整体环向应变及应变率参数评估急性心肌梗死大鼠不同程度心肌损伤的应用价值.方法 55只Wistar大鼠随机分为急性心肌梗死组(MI组)45只和假手术组(SO组)10只.MI组大鼠随机分为MI15组、MI30组和MI60组各15只,分别钳夹冠状动脉左前降支15 min、30 min、60 min,以建立不同梗死面积的急性心肌梗死模型.各组大鼠分别于基础状态和恢复灌注24 h后行超声心动图检查,记录左室乳头肌短轴高帧频二维图像,应用EchoPAC工作站分析获得左室乳头肌短轴整体收缩期峰值环向应变(GSc)和应变率(GSRc)值,并采用解剖M型测量左室舒张末期内径(LVIDd)和收缩末期内径(LVIDs)、短轴缩短率(FS)、射血分数(EF).实验结束后处死大鼠取出心脏行TTC染色并计算左室乳头肌短轴的梗死面积(AN).结果 ①MI15组、MI30组和MI60组的LVIDd和LVIDs测值均较基础状态和假手术组明显增加,FS和EF测值明显降低;MI60组的LVIDd和LVIDs测值均较MI15和MI30组明显增大,FS和EF测值明显降低(P<0.05);②MI15组、MI30组和MI60组GSc和GSRc测值均较假手术组明显减低;MI组的GSc和GSRc测值随缺血时间延长而显著降低(P<0.05);③GSc和GSRc与AN显著相关(P<0.01),相关系数分别为0.90和0.88;GSc和GSRe参数是AN的显著预测因子(P<0.01),标准回归系数(Beta)分别为0.558和0.491;④TTC染色显示AN随缺血时间延长而显著增加(P<0.05).结论 基于2D-STI技术的左室整体环向应变及应变率随心肌梗死面积增加而显著降低,该参数可准确评价急性心肌梗死后不同程度心肌损伤.

Value of two-dimensional speckle tracking imaging in assessing myocardial injury in various degree of rats

Objective To investigate the value of left ventricular global two-dimensional strain and strain rate index measured by two-dimensional speckle tracking imaging (2D-STI) in assessing myocardial injury in various degree of rats following acute myocardial infarction. Methods Fifty-five Wistar rats were randomly divided into myocardial infarction(MI) group ( n =45) and sham-operation(SO) group ( n = 10).To establish rats acute myocardial infarction model with different infarct extent, MI group were randomly divided into MI15 group,MI30 group and ML60 group( n = 15,respectively) which underwent occlusion of left anterior descending coronary artery for 15 minutes, 30 minutes and 60 minutes respectively. Echocardiography was performed at baseline and 24 hours after reperfusion. High frame rate twodimensional images were recorded from the left ventricular short-axis views at the papillary muscle level.Left ventricular global circumferential strain(GSc) and strain rate(GSRc) were measured using EchoPAC work station. Left ventricular internal diameter at diastole (LVIDd) and systole ( LVIDs), fractional shortening(FS) and ejection fraction(EF) were measured by anatomical M-model echocardiography. Area of necrosis(AN) of each segment was measured after triphenyl tetrazolium chloride(TTC) staining. Results ① Compared with baseline and SO group, LVIDd and LVIDs of MI15, MI30 and MI60 group significantly increased respectively,whereas FS and EF significantly decreased( P <0. 05). Compared with MI15 group and MI30 group, LVIDd and LVIDs of MI60 group significantly increased, whereas FS and EF significantly decreased(P <0. 05). ② Compared with baseline and SO group,GSc and GSRc of MI15 group, MI30 group and MI60 group significantly decreased. GSc and GSRc of MI group decreased with ischemia duration ( P <0.05). ③ GSc and GSRc significantly correlated with AN respectively ( P <0. 01) while the correlation coefficient was 0. 90 and 0. 88 respectively, and GSc and GSRc were significantly predictors of AN( P <0.01) while the Beta was 0.558 and 0.491 respectively.④AN increased with ischemia duration( P <0.05). Conclusions Left ventricular global circumferential strain and strain rate index measured by 2D-STI,which decreased significantly as the area of necrosis increased, can accurately assess myocardial injury after myocardial infarction in various degree.