超声血流向量成像评价健康比格犬心脏不同位点起搏左心室血流涡旋

Vector flow mapping for assessing Beagle dogsr left ventricular vortex in selective bi-polar single site cardiac pacing

目的应用超声血流向量成像（VFM）技术评价健康比格犬心脏不同位点起搏心动周期内左室流场涡旋分布、强度变化及心肌力学参数，探讨起搏状态下心腔内涡旋变化特征，为临床优化人工心脏起搏位点提供流体力学基础实验数据。方法分别采集8只健康比格犬开胸模型基础窦性心律状态和右室心尖、左室心尖和侧壁起搏状态下二维彩色多普勒血流图，导入血流向量标测软件分析图像，定性观察并比较不同状态下特定时相左室涡旋分布及强度涡量变化，应用速度向量标测软件分析左室心内膜下心肌力学参数，同时测量左室每搏输出量（LVSV）、射血分数（LVEF）、心输出量（LVCO）、dp／dt max和E／Vp。结果心脏各位点起搏LVsV、LVEF、LVCO和dp／dt max均较基础状态降低（P〈0．05），E／Vp起搏与基础状态间比较差异无统计学意义（P〉0．05），左室心尖和侧壁起搏LVSV、LVEF、LVCO均低于右室心尖起搏（Pd0．05）；与基础状态相比，不同位点起搏心动周期内左室腔内生理涡旋的方向、有序对称分布及涡旋强度发生改变，其中左室壁各位点起搏均导致了较右室心尖起搏更为明显的变化，左室心尖起搏导致异常最为明显。多变量回归分析中，基础状态收缩早期涡强分别与舒张晚期涡强和整体纵向应变独立相关（R2=0．63，P〈0．001及P=0．003）。结论心脏不同位点起搏导致了左室内血流涡旋状态改变，舒张晚期到收缩早期的持续涡旋从血流动力学表明舒张期与收缩期之间良好的耦联。

Objective To investigate the changes of left ventricular（LV） vortex strength（VS） and distribution during selective cardiac pacing in a phases of cardiac cycle using vector flow mapping techniques,and associate with LV mechanical performance,so as to provide basic experimental database for optimizing the sites of the artificial cardiac pacing in clinic conditions. Methods Eight heathy open-chest Beagle dog models were employed for selective right ventricular apical （RVAP）, left ventricular apical （LVAP） and lateral wall pacing （LVLP）. The standard two-dimensional apical three views with color Doppler flow and dynamic two-dimensional images were acquired consecutively in three cardiac cycles for further off-line analysis, conventional parameters were measured at same time. Results Compared with baseline, LVSV, LVEF, LVCO and dp/dtmax were both reduced, and the parameters obtained leftside cardiac pacing were lower than that of right ventricular pacing （ P 〈 0.05）, therer s no significant difference in E/Vp. The vortex pattern,distribution and vorticity at six typical phases induced by selective cardiac pacing were totally different from those at baseline with sinus rhythm, and leftside pacing were worsen than RVAP,the LVAP were most obvious. On multivariable regression analysis, the VS during ES （VSEs） at baseline was independently related to late-diastolic VS and longitudinal strain （R2 = 0.63, P 〈0.001 and P = 0.003,respectively）. Conclusions The selective cardiac pacing could induce intracardiac vortex changes and differ from that at baseline,and the persistence of vortex from late diastole into ES is a haemodynamic