斑点追踪成像评估小鼠心肌功能不全及纤维化的研究

Evaluation of mouse models of myocardial dysfunction and myocardial fibrosis by speckle tracking imaging

目的探讨二维超声斑点追踪成像技术评估小鼠心肌梗死模型局部心肌功能不全及心肌纤维化程度的应用价值。方法20只C57／B6小鼠随机分成两组：心肌梗死手术模型（MI）组10只和假手术（S0）组＋10只。实验小鼠于术后4周行超声心动图检查，应用EchoPac工作站分析左室乳头肌短轴观高帧频图像，测量各节段收缩期峰值径向应变（peak radical strain，PRS）及峰值径向应变率（peak radical strain rate，PRSR）。实验结束后处死小鼠，取出心脏行Masson染色观察心肌组织中的心肌纤维，计算心肌各节段纤维化百分比（percent segmental fibrosis，PSF）。结果与sO组相比，MI组各节段心肌收缩期PRS及PRSR均明显降低，差异有统计学意义（P〈0．01），MI组前间隔、前壁、侧壁的PRS及PRSR值明显低于其他节段（P〈0．05）；相对于SO组，MI组前间隔、前壁、侧壁、后壁心肌PSF明显升高（P〈0．01），相应节段PRS、PRSR与PSF呈负相关性（r=-0．88，P〈0．001；r=-0．77，P〈0．001）。结论应用二维超声斑点追踪成像技术评估小鼠心肌梗死模型心功能不全，可以准确量化局部心肌功能。该技术测量的PRS及PRSR与PSF显著相关，可作为无创监测心肌梗死后局部心肌纤维化的工具。

Objective To investigate the value of two-dimensional speckle tracking imaging （STI） in assessing regional myocardial dysfunction and myocardial fibrosis in a mouse model of myocardial infarction. Methods Twenty C57/B6 mice were randomly divided into two groups： myocardial infarction （MI） group （n = 10） and sham-operation （SO） group （ n = 10）. Echocardiography was performed four weeks after surgery. High frame rate two dimensional images were recorded in the left ventricular short axis views at the papillary muscle level and analysised at EchoPac workstation. Peak radical strain （PRS） and peak radical strain rate （PRSR） of each segment were measured at systolic period. Percent segmental fibrosis （PSF） was assessed from histological left ventricular cross sections stained by Masson trichrome. Results Compared with SO group, PRS and PRSR decreased significantly in all segments of MI group （P 〈 0.01 ）, especially in anterosepetal, anterior and lateral segments （ P 〈 0.05 ）. PSF of anterosepetal, anterior,lateral and posterior segments in MI group increased significantly than those in SO group（ P 〈 0.01） ,and were negatively correlated with PRS and PRSR of these segments（ r = - 0.88, P〈0. 001 ; r = -0.77, P〈0. 001）. Conclusions STI could accurately quantify regional myocardial function in a mouse model of myocardial infarction. Segmental radial strain and strain rate measured by STI were significantly correlated with PSF, which can be a non-invasive tool for monitoring myocardial fibrosis after myocardial infarction.