解剖M型超声、定量组织多普勒检测心肌梗死大鼠左室局部收缩功能

目的大鼠心肌梗死模型上,探讨急性心肌缺血、梗死及其演变过程中解剖M型超声(AME)、定量组织多普勒速度成像(QTVI)变化规律及特征,比较它们在检测局部心肌收缩功能变化中的相对价值。方法31只SD大鼠分成MI组(n=22)和对照组(n=9)。MI组大鼠在开胸手术下结扎左冠状动脉前降支(LAD),随后复苏饲养4周。对照组动物仅行假手术。应用超声显像仪分别同步记录术前、术后即刻、2周及4周的AME、QTVI图像或曲线,以AME观察左室壁局部收缩期与舒张期厚度(WTs、WTd)及局部室壁增厚率(WTF)、QTVI观察局部心肌内膜下、外膜下及全层室壁组织速度(SPVendo、SPVepi、SPV)。结果与术前基线及对照组对应阶段比较:术后即刻WTd、WTs及WTF呈降低趋势,术后2周及4周WTd、WTs和WTF均呈显著性降低。术后即刻SPVepi及SPV呈降低趋势,而SPVendo则呈显著性降低;术后2周及4周SPVendo、SPVepi及SPV均呈显著性降低。与术前基线及对照组对应阶段比较:大面积MI组WTF在术后即刻即显著降低,而中小面积MI组WTF在术后2周或以上才显著降低;无论大或中小面积MI组,术后即刻SPV即显著降低。AME确定的与组织学确定的心肌梗死的范围无显著性差异(0.28±0.14和0.35±0.13,P>0.05),且两者具有高度相关性(r=0.73,SEE=0.14,P<0.01)。结论AME和QTVI均能对缺血或梗死心肌进行局部心功能定量分析;心肌缺血或梗死面积大小影响AME、但可不影响QTVI对局部心功能异常的早期检测;AME可较好地确定缺血或梗死心肌的受累范围,而QTVI通过检测从心内膜下至心外膜下层心肌的速度梯度变化可区别不同层次的心肌功能。

Comparison of anatomic M-mode and tissue velocity imaging in quantification of regional left ventricular function in rat myocardial infarction model

Objective To investigate alterations of parameters derived by anatomic M-mode echocardiography(AME), quantitative tissue velocity imaging (QTVI) during the process from myocardial ischemia to infarction, and to compare the relative values of two imaging modalities in detection and quantification of regional left ventricular systolic function. Methods A rat model of myocardial ischemia/infarction was created by the procedures of open-chest operation and ligation of left anterior descending coronary artery (LAD) in 22 rats (MI-group), and 9 rats only with open-chest operation and without ligation of LAD (sham-operation) served as controls (CL-group). Echocardiography by using two new imaging modalities of AME and QTVI was performed pre-procedurally at baseline, and immediately, 2-week and 4-week after the procedures. The parameters included systolic and diastolic thickness of regional left ventricle (WTs and WTd) and systolic thickening fraction of regional left ventricle (WTF) derived by AME, subendo-, subepi-, and transmural myocardial tissue velocities (SPVendo, SPVepi and SPV) derived by QTVI. Results Comparing with those parameters measured at baseline pre-procedurally in MI-group and at the corresponding stages in CL-group, WTd, WTs and WTF trended to be insignificantly reduced immediately after the procedures, and significantly decreased 2-week and 4-week post-procedurally; SPVepi and SPV trended to be insignificantly decreased and SPVendo significantly decreased immediately post-procedurally, SPVepi, SPVendo and SPV significantly decreased 2-week and 4-week post-procedurally. Comparing with those parameters detected at baseline in MI-group and at the corresponding stages in CL-group, WTF markedly diminished immediately after the procedures in rats with larger size of MI, and until more than 2 weeks post-procedurally in rats with smaller size of MI; SPV markedly reduced immediately post-procedurally despite of MI size. The infracted sizes decided by AME and pathologically were not different (0.28±0.14 vs 0.35±0.13, P>0.05) with highly linear relationship between them (r=0.73, SEE=0.14, P<0.01). Conclusion Both AME and QTVI are able to quantitatively detect regional left ventricular systolic function; the size of myocardial ischemia/infarction may significantly influence the ability of AME, and may not affect QTVI in the earlier detection of regional left ventricular systolic function; AME may more accurately measure the size of myocardial infarction, QTVI may identify myocardial velocity gradient transmurally.