超声二维斑点追踪显像技术检测犬顿抑心肌跨壁力学状态的变化

目的 应用超声二维斑点追踪显像技术检测犬顿抑心肌心内、外膜纵向的应变变化,探讨顿抑心肌的跨壁力学变化及其随时间的变化规律。方法 12只犬左冠状动脉前降支结扎20 min,再灌注120 min,分别于结扎前、结扎期间、再灌注后即刻、30、60、90、120 min采集心尖切面图像。应用超声二维斑点追踪显像技术检测缺血及非缺血节段心内膜、心外膜、整体节段应变参数:纵向峰值应变(LS_peak)、峰值应变延迟时间(TPS_LS),并进行比较分析。结果 犬心肌左冠状动脉前降支结扎后、再灌注后即刻缺血节段心内、外膜、整体节段LS_peak明显减低,TPS_LS延长,且LS_peak以心内膜下心肌减低更明显;随再灌注时间延长,二维应变逐渐恢复,心外膜下心肌恢复更快,缺血节段整体心肌恢复正常时,心内膜下心肌仍未恢复正常。非缺血节段在左冠状动脉前降支结扎后、再灌注后即刻心内、外膜下LS_peak明显增加,TPS_LS延长,再灌注30 min恢复正常。结论 超声二维斑点追踪显像技术可检测犬顿抑心肌在缺血及再灌注阶段心内、外膜下心肌二维应变变化。

Evaluation of changes in transmural mechanics of stunned myocardium in dogs with speckle tracking imaging

Objective To explore the cross-wall mechanical change and its variation with time through evaluation on the systolic longitudinal strain changes of endocardium, epicardium overall canine stunned myocardium during ischemia and reperfusion with two-dimensional speckle tracking imaging (2D-STI). Methods Left anterior descending coronary artery of 12 dogs was ligated for 20 min and then reperfused for 120 min, respectively. Apex aspect images were acquired before ligation, during ligation period, reperfusing immediately and 30, 60, 90, 120 min after reperfusion, respectively. Two-dimensional ultrasound speckle tracking imaging was used to detect the systolic strain parameters of endocardium, epicardium in ischemia and non-ischemic segments: Peak longitudinal strain (LS_peak) and its delayed time to peak strain (TPS_LS), and a comparative analysis was done as well. Results During left anterior descending coronary artery ligation, immediately after reperfusion ischemic heart segment, LS_peak of endocardium, epicardium and overall myocardium decreased significantly, TPS_LS prolonged, and LS_peak reduced more obviously in endomyocardium. With the extension of reperfusion, strain parameters gradually restored, but the epicardial myocardium recovered faster, and ischemic myocardial segments as a whole returned to normal when the subendocardial did not yet return to normal. A marked increase of LS_peak and TPS_LS was found immediately after reperfusion in non-ischemic segments in the left anterior descending coronary artery ligation, and recovered to normal 30 min later. Conclusion Two-dimensional ultrasound speckle tracking imaging can detect two-dimensional strain change of endocardium and epicardium in dogs with ischemia and reperfusion.