急性心肌缺血状态下左心室心肌的力学研究

Mechanics study on Left Ventricular myocardial During Acute Myocardial Ischemia

目的通过构建动物急性心肌缺血模型,运用速度向量成像技术观察急性心肌缺血前、后左心室心肌的径向应变、周向应变的变化,探讨急性心肌缺血状态下左心室心肌部分力学变化规律。方法 9只杂种犬经开胸暴露心脏后,通过结扎左前降支造成急性心肌缺血,分别采集缺血前、后左心室不同的短轴二维动态灰阶切面图像,通过离线速度向量成像技术,观察左心室心内膜下心肌16节段的径向应变及周向应变的变化规律。结果缺血前左心室同一室壁心内膜下心肌周向应变从基底水平节段至心尖水平节段依次增大;缺血后这一变化规律消失,且所有节段周向应变均降低。缺血前同一室壁径向应变基底水平节段均低于乳头肌节水平节段和心尖水平节段,所有室壁乳头肌节段与心尖节段径向应力呈均一性变化;缺血后,出现部分节段径向应变增大和相应节段应变减小。结论急性心肌缺血早期,左心室心内膜下心肌应力状态异常改变是左心室功能重构和结构重构的重要力学基础。

Objective To investigate segmental subendocardial mechanical pattern of left ventricle （LV） during acute myocardial ischemia using ultrasonic velocity vector imaging（VVI）,and to demonstrate LV subendocardial mechanicals changs for the precise quantitative evaluation of early ischemic myocardial function.MethodsNine mongrel dogs after thoracotomy and the heart was exposed by ligation of the left anterior descending branch of the induced acute myocardial ischemia were collected before ischemia, after different left ventricular short axis two-dimensional dynamic grey scale of image plane, by off-line velocity vector imaging were left ventricular endocardium myocardial 16 segments of radial strain and the variation of circumferential strain.Results Beforeischemia,the myocardial circumferential strain of the left ventricle was increased from the basal level to the apical level in the same wall, thechanges disappear after ischemia, andthecircumferential strain of all segments decreased.Before ischemia with one compartment wall radial strain basal segment level were lower than those of the papillary muscle level segments and apical level segments, all room wall papillary myotome segments and apical section radial stress appeared as homogeneous change, after ischemia, part of segmental radial strain increases and the corresponding segment of strain is reduced.Conclusion Demonstrates that abnormal mechanical pattern of LV subendocardium induced by acute myocardial ischemia is the important pathophysiological mechanism of LV functional and anatomical remodeling.