单点双极选择性心脏起搏犬左心室腔内流场状态的超声观察

Ultrasonic visualization of intracardiac fluid field of beagle's left ventricle during selective bi-polar single site cardiac pacing

目的采用基于多普勒血流成像原理的血流速度向量标测技术观察不同位点单点双极心脏起搏状态左心室腔内流场变化。方法 9只Beagle犬开胸动物模型,分别选择性起搏右心室心尖、左心室心尖和左心室侧壁,获取不同心脏电机械兴奋状态下连续3个心动周期的标准心尖四腔、两腔和左心室长轴切面二维彩色多普勒血流图。通过血流速度向量工作站,得到左心室心腔内血流二维速度向量、流线和涡流成像。通过在流线成像基础上同时设置左心室心尖、乳头肌和基底水平3条取样线获取跨线速度向量分布。在心动周期6个特定时相同时观察上述3个切面血液流场状态。结果采用血流速度向量标测技术能够观察到特定时相左心室心腔内的血液流场状态,与基础窦性心律状态比较心脏起搏状态收缩期和舒张期左心室腔内血液流场的有序梯度分布和生理涡流状态遭到破坏或改变。左心室壁各位点起搏导致的左心室腔内流场异常状态均较右心室心尖起搏严重,其中左心室心尖位点起搏导致的左心室腔内流场状态改变程度较左心室侧壁起搏明显。结论选择性心室起搏导致了左心室心腔内流场状态改变,应用血流速度向量标测技术能够检测到心脏起搏导致的左心室心腔内流场变化。

Objective To visualize the dynamic changes of intracardiac fluid field of left ventricle during selective cardiac pacing using ultrasonic vector flow mapping techniques. Methods Nine healthy open-chest beagle dog models were employed for selective right ventricular apical, left ventricular apical and lateral wall pacing. The standard two-dimensional apical four, apical two and left ventricular long axis views with color Doppler flow were acquired consecutively in three cardiac cycles for further off-fine analysis. The dynamic images of intracardiac two-dimensional velocity vector, stream-line and vortex were derived respectively using a dedicated vector flow mapping work-station. Three sample lines were placed across the left ventricular chamber at the levels of apex, papillary muscle and base simultaneously to display the cross-line velocity vector distribution at six typical phases of cardiac cycle in three standard apical long axis views. Results The dynamic changes of intracardiac fluid field of left ventricle could be visualized using dedicated flow velocity vector mapping techniques. The fluid field patterns at six typical phases in three cardiac cycles induced by selective cardiac pacing respectively were totally different from those at baseline with sinus rhythm. Compared with the baseline, the sequential velocity gradient distribution from the base to apex and the vortex formation during systole and diastole were changed and disturbed obviously during cardiac pacing. The patterns of intracardiac fluid field of left ventricle induced by left side pacing were more turbulent than that during right ventricular apical pacing, and the pattern induced by left ventricular apical pacing was worse than that during lateral wall pacing. Conclusions The selective cardiac pacing could introduce intracardiac fluid field change of left ventricle and differ from that at baseline. The Doppler principle based flow velocity vector mapping techniques could be used to demonstrate the abnormal changes of intracardiac fluid field patterns induced by cardiac pacing.