Layer-specific strain of speckle tracking imaging to assess longitudinal myocardial function in pharmacological postconditioning rabbits′ model

Objective To evaluate the effect of pharmacological postconditioning on longitudinal myocardial function in rabbits′ model of myocardial inshemia-reperfusion using layer-specific strain of ultrasound speckle tracking imaging. Methods Forty healthy rabbits were randomly divided into two groups: ischemia-reperfusion group(IR) and pharmacological postconditioning group(ATP-PPost). Echocardiography examinations were performed at baseline, 45 min after ligation and 30 min, 60 min, 120 min after reperfusion. Pathological examinations were applied in two rabbits randomly selected from each group at 45 min after ligation and 30 min, 60 min after reperfusion and at the end of experiment. Results ①After coronary artery ligation, left ventricular ejection fraction (LVEF) decreased in two groups(P<0.05) and longitudinal systolic strain(SLsys) of 3 myocardial layers decreased in two groups (P<0.01). And the SLsys in the endocardium had greater variation than that in the epicardium. ②Compared with that after ligation, the SLsys of all myocardial layers increased at 30 min after reperfusion in ATP-PPost group ( P<0.01), and the SLsys in endocardial layer kept increasing with the time of reperfusion(P<0.05). And the SLsys of 3 myocardial layers were significantly higher in ATP-PPost group than those in IR group(P<0.01). ③In two groups, the values of SLsys were decreasing from endocardial layer to epicardial layer. They were higher in the endocardium than those in the epicardium at any time(P<0.01 and P<0.05). Conclusions Layer-specific strain of STI can evaluate exactly the regional myocardial function of rabbit myocardial pharmacological-postconditioning model. SLsys of endocardial layer is more sensitive to myocardial ischemia than that of epicardial layer. Key words: Echocardiography; Myocardial ischemia; Postconditioning; Adenosine; Speckle tracking imaging