中文摘要：

目的 应用二维超声斑点跟踪成像技术评价犬右心室心尖起搏状态下等容收缩期左心室前壁心肌力学状态,评价起搏导致的局部心肌力学状态重构.方法 将8只健康雌性比格犬分为对照组和右心室心尖起搏组,每组4只.分别采集两组无起搏和右心室心尖起搏状态下左心室前壁标记点处连续3个心动周期二维超声灰阶图像,脱机应用STI软件对图像上标记位点处心内膜下、中层和心外膜下心肌应变进行分析,获取力学参数,同时测量起搏前、后等容收缩期时间.对所有数据进行统计学分析.结果 右心室心尖起搏后等容收缩期较对照组持续时间延长（P＜0.01）.标记点处各层次应变值与位移值起搏前后具有不同程度差异,部分位点差异有统计学意义（P＜0.05）,部分位点应变与位移方向起搏前、后相反,主要体现在室间隔和心尖部.结论 犬右心室心尖起搏后等容收缩期延长;犬心肌力学状态异常重构即刻产生并持续较长时间.

英文摘要：

Objective To assess the left ventricular myocardium mechanics reconstruction of healthy canine in isovolumetric contraction phase （ICP） during right ventricular apical loading pacing （RVAP）tentatively based on ultrasonic speckle tracking imaging （STI）.Methods Eight healthy female Beagle canine were randomly divided into RVAP group and contrast group （each n=4）.The strain （circumferential strain,CS; radial strain,RS; longitudinal strain,LS） and the displacement parameters （radial displacement,RaD; rotational displacement,RoD; longitudinal displacement,LD） at local marked myocardium （subepicardial myocardium,sub-epi; midwall myocardium,mid; subendocardial myocardium,sun-edo） were derived with a dedicated off-line STI workstation.Meanwhile the isovolumetric systolic interval before and after pacing was measured.All data were statistically analyzed.Results After RVAP pacing,the ICP was longer than that of contrast group（P＜0.01）.At the sites of ventricular septum and apex,LD and LS increased in a reversal direction （P＜0.05） and RoD with different directions of rotation before and afterpacing （P＜0.05）.The direction and amplitude of RaD and CS before and after pacing were all statistically different （P＜0.05） and RS with a different directions （P＜0.05）.LD,LS,RoD and RaD at sub-epi and mid had statistical difference after RVAP pacing （P＜0.05）.Conclusion Isometric contraction interval of left ventricle is much longer than that of contrast group during RVAP pacing.The reconstruction of myocardial mechanics induced by RVAP mainly occurred at ventricular septum and apex instantly and persistently.