Value of two-dimensional speckle tracking imaging on assessing the local function and coronary collateral circulation of acute myocardial ischemia in dogs

Abstract

Objective To evaluate the applicable value of two - dimensional speckle tracking imaging on assessing the local function and coronary collateral circulation of acute myocardial ischemia in dogs.Methods Open-chest model to induce acute myocardial ischemia in 10 dogs was established by ligating their anterior descending coronary artery(LAD). Two-dimensional dynamic gray- scale images of two standard left ventricular short axis views at the levels of mitral annulus and papillary muscle were acquired for the off -line comparative analysis before the operation and 0, 30, 60, 120, 240 and 360 minutes after the operation respectively. Peak systolic circumferential strain(CS), peak systolic radial strain(RS) and left ventricular fraction shortenting(LVFS) of 12 segments at the levels of mitral annulus and papillary muscle were analyzed with QLAB software. After the lab experiment,the fresh hearts of dogs were dyed by TTC.Results ①Compared with the preoperative value , the peak systolic CS and RS of ischemia myocardial regions(anteroseptum,anterior and lateral) in left ventricular short-axis decreased significantly( P ＜0. 05)during 30 to 60 minutes after ligating LAD. Sixty minutes later, the peak systolic CS and RS had a tendency to return to the level before the operation,although the statistical difference was existing. The peak systolic RS and CS also decreased in certain nonischemic regions (inferolateral and inferior). But CS and RS in inferoseptal regions didn't alter significantly. ②Compared with the preoperative value,LVFS in the ischemia regions were significantly decreased( P ＜0.05), while nonischemic regions had no significant difference. ③The results of TTC dyeing showed that the infarcted regions in left ventricular short-axis were anteroseptum, anterior and lateral with blood supplied by LAD, which were consistent with the results of RS and CS. Conclusions RS and CS,as the parameters of myocardial strain may reflect the range and extent of acute myocardial ischemia,and the strain changes of local myocardial segments after the construction of coronary collateral circulatory. Key words: Echocardiography; Myocardial ischemia; Ventricular function,left ; Collateral circulation; Speckle tracking imaging