二维斑点追踪技术评价犬缺血心肌局部功能及侧支循环的应用价值

目的 探讨二维斑点追踪技术评价犬缺血心肌局部功能及侧支循环建立的应用价值.方法 10只杂种犬,结扎左冠状动脉前降支(LAD)主干建立急性心肌缺血模型.分别于术前、LAD结扎后即刻、30、60、180、240、360 min,采集左心室短轴二尖瓣水平及乳头肌水平二维灰阶动态声像图,QLAB软件分析左心室短轴基底部及乳头肌水平12节段心肌整体收缩期平均峰值周向应变(CS)、径向应变(RS)及左室短轴缩短率(LVFS)的变化.实验结束后行心肌组织氯化三苯基四氮唑(TTC)染色.结果 ①与术前相比,LAD结扎术后30～60 min,左心室短轴缺血节段(前间隔、前壁及侧壁)的心肌应变CS及RS收缩期峰值均显著降低(P＜0.05);60 min后CS及RS收缩期峰值均有恢复趋势,但与术前差异仍有统计学意义.非缺血节段后壁及下壁术后部分CS及RS收缩期峰值较术前有所下降(P＜0.05),后间隔CS及RS无明显变化.②与术前相比,LAD结扎术后60～360 min,左心室短轴缺血节段(前间隔、前壁及侧壁)的LVFS均显著降低(P＜0.05),非缺血节段LVFS均无显著改变.③TTC染色结果显示,左心室短轴心肌梗死节段为LAD供血的前间隔、前壁及侧壁,与CS和RS的结果相一致.结论 心肌应变参数CS、RS能够敏感反映急性心肌缺血的范围、程度及侧支循环建立后局部心肌节段应变的变化.

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

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.