急性心肌缺血单点双极起搏犬左心室功能的超声三维斑点追踪研究

目的应用超声三维斑点追踪成像技术评价心室单点双极起搏对急性心肌缺血犬左心室壁心肌力学和左心室功能的影响。方法开胸比格犬10只,分别采集基础状态、急性心肌缺血状态和缺血后右心室心尖、左心室心尖、左心室侧壁单点双极起搏状态一个完整心动周期的左心室三维全容积实时图像;同步记录左心室压力变化时间曲线并获取左心室射血压力(LVEP)和收缩期压力最大上升速率(dp/dtmax)。用超声三维斑点追踪分析软件分别提取不同状态左心室壁径向三维应变图、左心室壁径向三维峰值应变(PRS)和左心室收缩末期容积(LVESV)、舒张末期容积(LVEDV)、每搏输出量(LVSV)、射血分数(LVEF)、心输出量(LVCO)等参数。定性观察并比较不同状态左心室壁不同节段心肌的径向三维应变同步性,线性校正并两两比较不同状态左心室功能参数;相关分析不同状态左心室壁整体径向三维峰值应变与左心室容量、压力参数。结果①左心室壁径向三维应变图可视化分析提示急性心肌缺血后心室起搏状态左心室壁机械运动不同步程度较基础状态和急性心肌缺血状态明显;②急性心肌缺血状态左心室壁整体及16个不同节段心肌的PRS、LVEF、LVCO、LVEP和dp/dtmax均较基础状态减低(P0.05);③与急性心肌缺血状态比较,心室起搏状态左心室壁整体PRS增大(P0.05),而左心室容量参数、压力参数差异无统计学意义;④不同起搏状态间左心室壁整体PRS、LVESV、LVEDV、LVSV、LVEF、LVCO、LVEP和dp/dtmax差异无统计学意义(P0.05);⑤不同状态左心室壁整体PRS与LVSV、LVEF和LVCO呈线性正相关(r=0.628~0.889,P0.05)。结论应用超声三维斑点追踪成像技术发现心室单点双极起搏能够增强心肌缺血状态左心室壁心肌收缩力,但同时导致左心室壁机械运动不同步程度加重,不能有效改善因急性心肌缺血受损的左心室整体功能。

The study on left ventricular function in acute ischemic canine during one point dipolar pacing using three-dimensional ultrasonic speckle tracking

Objective To evaluate the one point dipolar pacing effects on myocardial mechanics and left ventricular function of acute ischemic canine using ultrasonic three-dimensional（3D） speckle tracking imaging technique. Methods Ten open-chest beagles with ventricular 3D full volumetric real-time imaging in a completed cardiac cycle were acquired respectively at baseline （BASE）, and during acute ischemia （ISCH） , post-ischemic right ventricular apex, left ventricular apex and lateral wall one point dipolar pacing. Left ventricular pressure-time sequence curve was recorded simultaneously for achieving left ejection pressure （LVEP） and the maximal upstroke velocity of left ventricular systolic pressure（ dp/dtmax ）. Radial 3D strain maps and radial 3D peak strain of left ventricular wall, and left ventricular end systolic volume, diastolic volume, stroke volume, ejection fraction, cardiac output of different states were extracted respectively using ultrasonic 3D speckle tracking analysis software. The radial 3D strain synchrony of left ventricular wall during different states was qualitatively observed and compared. All parameters of left ventricular function in different mechanic patterns were linearly correlated each other. At different states, the correlation test was applied respectively between the global 3D peak strain of left ventricular wall and global volumetric parameters or pressure parameters. Results （1）The mechanical asynchrony of left ventricular wall during different post-ischemic ventricular pacings was worse than those at BASE and during ISCH on the radial 3D strain maps of left ventricular wall;（2）Compared with BASE： left ventrieular global and its 16 myocardial segments radial peak 3D strain, left ventrieular ejection fraction ,cardiac output, left ventricular ejection pressure and the maximal upstroke velocity of left ventricular systolic pressure decreased significantly during ISCH （ P 〈 0.05 ） ;（3）Compared with ISCH： statistic significant increase was found for the global peak radial 3D strain of left ventricular wall（ P 〈0. 05 ） , but left ventricular stroke volume and left ventricular ejection fraction did not improve in all post-isehemic pacing patterns ; （4）No significant difference of LVESV, LVEDV, LVSV, LVEF, LVCO, LVEP and left ventricular dp/dtmax between each post-ischemic pacing patterns （ P 〉 0.05 ） was found;（5）The statistical significant linear correlations between the global 3D peak strain of left ventricular wall and left ventricular stroke volume, and left ventricular ejection fraction, and cardiac output in different pacing patterns were found. Conclusions Using ultrasonic 3D speckle tracking technique, The left ventricular myocardial contractility of ISCH beagles was improved via one point dipolar pacing, but the mechanical asynchrony was aggravated; therefore, ventricular one point dipolar pacing could not improve acute-ischemiadamaged left ventricular global function effectively.