中文摘要：

目的探讨正常人及左束支传导阻滞（left bundle branch block，LBBB）患者左心室内膜、中层及外膜圆周应变的变化。方法选取40例LBBB患者，根据左室射血分数（left ventricular ejection fraction，LVEF）分为两组，LBBB1组（LVEF≥50％）和LBBB2组（LVEF〈50％），另外选取25例健康人，分别采集胸骨旁左心室短轴二尖瓣水平、乳头肌水平及心尖水平图像，应用分层斑点追踪技术分析左心室内膜、中层及外膜圆周应变。结果与正常对照组相比，LBBB1组外膜及中层圆周应变在二尖瓣水平及乳头肌水平差异无统计学意义（P〉0．01），在心尖水平差异有统计学意义（P=0．004），内膜圆周应变在二尖瓣水平差异无统计学意义（P〉0．01），在乳头肌及心尖水平差异均有显著统计学意义（P=0．000）；与正常对照组和LBBB1组相比，LBBB2组内膜、中层及外膜圆周应变在短轴各个水平差异均有显著统计学意义（P=0．000）。结论心尖水平内膜圆周应变在LVEF正常的LBBB患者即发生明显的改变，可以较早地提供诊断信息。

英文摘要：

Objective To evaluate the left ventricular systolic circumferential strain by layer-specific speckle tracking imaging in healthy volunteers and patients with left bundle branch block （LBBB）. Methods Forty patients with LBBB were divided into two groups, LBBB1 group l-left ventricular ejection fraction （LVEF≥50%] and LBBB2 group （LVEF〈50%）, and 25 healthy subjects were selected as the control group. High frame rate two-dimensional images were recorded from the left ventricular short-axis views at the levels of the mitral annulus, papillary muscle and apex respectively. The peak systolic circumferential strain of the endocardium, myocardium and epicardium were measured using layer-specific strain software. Results The circumferential strain of the epicardium and myocardium at the level of the apex showed a statistically significant difference between the LBBB1 group and the control group （ P = 0. 004）, while there was no statistically significant difference demonstrated at the levels of the mitral annulus and papillary muscle（ P 〉0.01）. The circumferential strain of the endocardium at the levels of the papillary muscle and apex showed a statistically significant difference between the LBBB1 group and the control group（ P = 0. 000）, while there was no statistically significant difference demonstrated at the level of the mitral annulus （ P 〉0.01 ）. The circumferential strain of the endocardium, myocardium and epicardium at the three short- axis view levels showed statistically significant differences between the LBBB2 group and the control or LBBB1 groups respectively（ P = 0.000）. Conclusions The circumferential strain of the endocardium at the level of the apex can provide more information about disease prognosis, especially in LBBB patients with a LVEF of ≥50%.