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目的:应用二维斑点追踪显像(2D-STI)分层应变技术评价急性心肌缺血早期左室整体和局部收缩功能。方法:对40只健康大白兔开胸行冠状动脉左室支结扎术建立急性心肌缺血模型,采用心脏超声诊断仪于术前、术后分别采集心尖四腔心、长轴、二腔心切面以及短轴二尖瓣水平、乳头肌水平、心尖水平切面二维动态图像。应用GE Echo PAC软件脱机分析左室整体应变及18节段的收缩期纵向、周向三层心肌(心内膜下心肌、中层心肌、心外膜下心肌)峰值应变。结果:对40只兔子进行长轴纵向应变分析;由于短轴图像质量原因,对成功追踪短轴切面的30只兔子进行周向应变分析。常规参数:兔术前、术后心率(HR)的差异有统计学意义(P<0.05),而室间隔厚度(IVST)、左室后壁厚度(LVPWT)、左室舒张末期内径(LVDd)、左房内径(LAD)、左室射血分数(LVEF)差异均无统计学意义(P>0.05)。整体应变:左室三层心肌整体纵向应变(GLS)、整体周向应变(GCS)及整体跨壁梯度ΔGLS、ΔGCS术后均显著低于术前(P<0.001)。左室GLS、GCS自心内膜下心肌至心外膜下心肌逐层递减(P<0.001)。长轴节段应变:左室侧壁、前间隔、前壁心内膜下心肌、中层心肌、心外膜下心肌纵向收缩期峰值应变术后均显著低于术前(P<0.05)。中间段及心尖段左室下、后壁心内膜下心肌、中层心肌、心外膜下心肌纵向收缩期峰值应变术后均显著低于术前(P<0.05)。基底段、中间段后间隔及基底段下、后壁三层心肌的纵向收缩期峰值应变术前、术后的差异无统计学意义(P>0.05),但术后低于术前。短轴节段应变:中间段左室前壁、侧壁、下壁心内膜下心肌及基底段前间隔、后间隔的心外膜下心肌的周向收缩期峰值应变术后均显著低于结扎前(P<0.05)。其余各节段三层心肌周向收缩期峰值应变的术前、术后的差异无统计学意义(P>0.05),但术后较结扎前有所下降。结论:2D-STI分层应变技术通过分析兔急性心肌缺血早期左室各节段的纵向、周向分层应变,能更加精确评价急性心肌缺血早期左室整体和局部收缩功能。
Objective: To evaluate the global left ventricular regional and regional systolic function in early stage of acute myocardial ischemia by 2D-STI stratified strain technique. Methods: Acute myocardial ischemia model was established in 40 healthy white rabbits underwent thoracotomy coronary artery ligation. The heart apex, four-chamber heart, long axis, And short-axis mitral valve level, papillary muscle level, apical horizontal section of the two-dimensional dynamic images. GE Echo PAC software was used to analyze the left ventricular total strain and the peak strain of longitudinal and circumferential three layers of myocardium (subendocardium, middle myocardium and epicardial myocardium) in 18 segments during systole. Results: Longitudinal longitudinal strain analysis was performed on 40 rabbits. A circumferential strain analysis was performed on 30 rabbits successfully tracking the short axis view due to the short-axis image quality. Conventional parameters: The preoperative and postoperative heart rate (HR) in rabbits were significantly different (P <0.05), while the interventricular septum thickness (IVST), left ventricular posterior wall thickness (LVPWT), left ventricular end diastolic diameter (LVDd) (LAD), left ventricular ejection fraction (LVEF) were not significantly different (P> 0.05). Overall strain: Left ventricular three-dimensional myocardial gross longitudinal strain (GLS), global circumferential strain (GCS) and overall transmural gradient ΔGLS, ΔGCS postoperative were significantly lower than preoperative (P <0.001). Left ventricular GLS, GCS decreased from endocardial to epicardial myocardium layer by layer (P <0.001). Longitudinal segmental strain: left ventricular wall, anterior septum, anterior myocardial subepicardial, middle myocardium, epicardial longitudinal myocardial systolic peak strain were significantly lower than preoperative (P <0.05). In the middle segment and the apical segment, the left ventricular and posterior wall of the subendocardial, midmyocardial, and subependymal myocardium were significantly lower than those before surgery (P <0.05). There was no significant difference in peak strain between the basilar segment, the middle segment and the inferior segment of the basilar segment and the posterior wall in the longitudinal systolic (P> 0.05), but lower than preoperative. Stub strain: the middle segment of the left ventricular anterior wall, the inferior wall of the subependymal myocardium and basal segment anterior septum and posterior septal subepicardial myocardial systolic peak after the peak strain were significantly lower than Before ligation (P <0.05). The preoperative and postoperative differences in peak strain of three layers of myocardial systolic in the other three segments were not statistically significant (P> 0.05), but decreased after the operation. Conclusion: The 2D-STI stratified strain technique can evaluate the left ventricular global and regional systolic function more accurately by analyzing the longitudinal and circumferential stratified strata of left ventricular segments in early stage of acute myocardial ischemia in rabbits.