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

Abstract

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. Key words: Echocardiography; Ventricular function,left; Myocardial infarctions Two-dimensional strain