Objective To analyze the endocardial and epicardial strain by ultrasound biomicroscopy (UBM) and two-dimensional speckle tracking imaging (2D-STI) for identify of left ventricular (LV) myocardial dysfunction. Methods A total of 24 mdx mice (C57BL/10ScSn-Dmdmdx/J) and 24 control mice (C57BL) were examined by ultrasound at 3, 6, 9, 12 months. Two-dimensional images of parasternal left ventricle (LV) long-axis view and short-axis at the midventricular level were acquired and the measurements such as the LV size, ejection fraction (EF) and fraction shortening (FS) were gotten. Endocardial and epicardial strain in longitudinal, circumferential and radial directions were analyzed by using special software. Peak systolic strain (PK) of all directions were obtained. Results Compared with the controls, significant LV remodeling and dysfunction were detected by M-mode UBM from 9 months, including the increase of left ventricular end-dias-tolic dimension (LVEDD), left ventricular end-systolic dimension (LVESD), left ventricular end-diastolic volume (LV-EDV), left ventricular end-systolic volume (LVESV) and the decrease of EF and FS. There was statistical difference between mdx and the control mice of the same age. 2D-STI could detect myocardial dysfunction of 6 months in mdx mice. Compared with the mdx mice of 3 months, the endocardial strain of the 6, 9 and 12 months mdx mice decreased significantly. There were significant differences among mdx mice of 6, 9 and 12 months, also between the mdx and the control mice of the same age. For the epicardial longitudinal and circumferential strain, compared with mdx mice of 3 months, statistical difference appeared only in 9 and 12 months mdx mice. Compared with the control mice of the same age, there were statistical differences in 9 and 12 months mdx for the peak systolic strain of longitudinal epicardial strain and circumferential epicardial strain. Conclusion Systolic function decreased significantly in 6 months mdx mice, which can be detected by UBM 2D-STI. However, M-mode echocardiography can only detect the systolic dysfunction of mdx mice aged over 9 months.%目的 应用超声生物显微镜(UBM)二维斑点追踪应变成像(2D-STI)评价mdx小鼠/S内、外膜下心肌收缩功能异常.方法 对24只mdx小鼠(C57BL/10ScSn-Dmdmdx/J)和24只正常对照小鼠(C57BL/10ScSn)进行研究.小鼠分别在3、6、9和12月龄时接受超声检查,常规心动图采集胸骨旁左心室(LV)长轴、乳头肌水平LV短轴二维图像,测量LV腔体积、射血分数(EF)及内径缩短率(FS)等指标.脱机分析两个不同切面LV心肌内外膜的纵向应变、圆周向应变及径向应变的收缩期峰值.结果 M型常规超声心动图发现,与正常对照小鼠相比,9月龄mdx小鼠心脏收缩功能异常,包括LV舒张末期内径(LVEDD)、LV收缩末期内径(LVESD)、LV舒张末期容积(LVEDV)和LV收缩末期容积(LVESV)增加,EF和FS降低.2D-STI分析发现6月龄mdx小鼠心脏收缩功能异常,与3月龄小鼠相比,6、9和12月龄小鼠的峰值应变(长轴、径向及圆周向)显著下降,6月龄与9月龄小鼠之间、9月和12月龄小鼠之间差异显著,与同期正常对照小鼠测值间差异也有统计学意义；而外膜下长轴及圆周向应变,与3月龄小鼠相比,9和12月龄时比较差异有统计学意义,与同月龄正常对照小鼠相比,9、12月龄mdx小鼠外膜下心肌长轴向应变及圆周向应变的峰值应变差异有统计学意义.结论 mdx小鼠6月龄时已经出现心肌收缩功能减低.UBM 2D-STI可发现这种变化,而传统M型超声心动图仅能发现9月龄及以上的心肌收缩功能异常.
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