【摘要】 目的采用超声速度向量成像技术评价急性心肌缺血犬左心室收缩期心内膜下心肌力学变化规律。方法对12只健康比格犬结扎冠状动脉左前降支制作急性心肌缺血模型,采集缺血前后左心室二尖瓣口水平、乳头肌水平、心尖水平动态二维灰阶动态图像;获取左心室不同水平各节段缺血前后心内膜下心肌周向应变、径向应变、旋转角度与径向位移;分析同一节段心肌周向和径向应变与旋转角度的相关性,及两个相邻节段心肌周向应变差值(ΔCS)与相应节段心肌旋转角度和径向位移的相关性。结果缺血前左心室心内膜下心肌同一室壁周向应变、旋转角度从基底段到心尖段依次增大,缺血后这一力学状态发生改变,其中前间隔基底段周向应变大于心尖节段(P<0.05),后间隔中段周向应变大于心尖节段(P<0.05);后壁基底段旋转角度大于中段(P<0.01)、下壁中段旋转角度小于心尖节段(P<0.05)、前间隔中段旋转角度小于心尖节段(P<0.05)。缺血前心尖水平切面相邻两个节段心肌ΔCS与其相应节段心肌的旋转角度呈线性相关(r=0.609～0.739,P<0.05或P<0.01);缺血前左心室心内膜下心肌同一室壁乳头肌水平节段与基底水平节段心肌ΔCS与其乳头肌节段心肌的径向位移呈线性相关(r=0.657～0.852,P<0.05或P<0.01),缺血后相关性消失。结论缺血前左心室心内膜下心肌相邻两个节段间的ΔCS与对应节段心肌旋转角度、径向位移的线性相关提示,相邻两个节段心肌间的ΔCS与心尖节段旋转运动以及左心室心腔向心性收缩密切相关。急性心肌缺血状态下,左心室心内膜下心肌应变状态异常改变是左心室重构的重要力学基础。更多还原

【Abstract】 Objective To investigate segmental subendocardial mechanical pattern of left ventricle(LV) during acute myocardial ischemia by ultrasonic velocity vector imaging(VVI),and to demonstrate LV subendocardial mechanical changes by accurate quantitative assessment on early ischemic myocardial function.Methods Twelve healthy Beagle dogs were used for echocardiographic scanning from LV base to apex,and three short-axis views of dynamic gray-scale images at the levels of mitral annulus,papillary muscle and apex before the left anterior descending coronary(LAD) ligation and 20 minutes after acquired.The segmental subendocardial mechanical parameters of LV at the subendocardiaum including circumferential strain(CS),radial strain(RS),rotation angle(RA) and radial displacement(RD) were derived from dynamic gray-scale images using a dedicated VVI workstation.The linear correlationship was analyzed among the segmental subendocardial CS,circumferential strain difference(ΔCS) of the two adjacent segments and RA,RD respectively.Results The CS and the RA of segmental subendocardium increased from LV base to apex.However,this mechanical pattern changed after acute myocardial ischemia.Before the LAD ligation,a linear correlation-ship was demonstrated between the ΔCS of the two adjacent segmental subendocardium and RA at LV apical level(r=0.609-0.739,P<0.05 or P<0.01,in four segments).A significant linear correlation was demonstrated between the ΔCS of the regional subendocardium from base level to midwall level at one ventricular wall and the RD of the midwall(r=0.657-0.852,P<0.05 or P<0.01,in six segments).All of these spatial correlation-ship changed after acute myocardial ischemia.ConclusionsThis study demonstrated that the ΔCS of the subendocardium between the two adjacent segments at LV apical level was mainly related to counterclockwise rotation at LV apex,and the ΔCS of the two adjacent segmental subendocardium at the same LV wall from the base and the midwall levels showed the RD of LV subendocardial in the radial direction during LV systole before LAD ligation.Abnormal mechanical pattern of LV subendocardium induced by acute myocardial ischemia is important for functional and anatomical remodeling in pathophysiological mechanism of LV.更多还原