Effect of the prosthetic mitral valve on vortex dynamics and turbulence of the left ventricular flow
Effect of the prosthetic mitral valve on vortex dynamics and turbulence of the left ventricular flow
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DOI：
10.1063/1.3371720
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发表时间：
2010-04-01
影响因子：
4.6
通讯作者：
Cenedese, A.
中科院分区：
文献类型：
--
作者：
Querzoli, G.;Fortini, S.;Cenedese, A.
在二尖瓣位置植入机械心脏瓣膜对心室血流有很大影响。这些变化包括舒张期产生的旋涡结构的动力学改变和湍流的发生，可能影响心脏泵的效率或引起血细胞损伤。当通过二尖瓣口的血流改变时，左心室血流动力学的改变，在体外使用硅橡胶，柔性心室模型进行了研究。利用图像分析技术——特征跟踪，在空间和时间上测量速度场。进行了三个系列的实验：一个是高帽流入速度曲线（原理上类似于生理条件），两个是不同设计的机械假体瓣膜，安装在二尖瓣位置——一个单片瓣膜和另一个双片瓣膜。在每个系列的跑步中，通过改变搏量来检查两种不同的心输出量。用相平均速度场和紊流波动二阶矩的方法研究了该流体的流动。结果表明，透射流的改变深刻地改变了舒张期第一阶段产生的相干结构与舒张期第二阶段进入射流之间的相互作用。在比较的情况下，顶帽流入提供了最优的收缩功能的连贯结构。双小叶阀产生的流动保留了顶帽流入的大部分有益特征，而单小叶阀产生的强射流阻碍了舒张末期大连贯结构的持久性。此外，与机械阀的测量值相比，更平滑的流型引起的平均剪切速率值几乎减少了一半。最后，湍流统计分析表明，与双叶阀相比，单叶阀产生更高的湍流强度，并且在高帽流入时，没有完全过渡到湍流。
Mechanical heart valves implanted in mitral position have a great effect on the ventricular flow. Changes include alteration of the dynamics of the vortical structures generated during the diastole and the onset of turbulence, possibly affecting the efficiency of the heart pump or causing blood cell damage. Modifications to the hemodynamics in the left ventricle, when the inflow through the mitral orifice is altered, were investigated in vitro using a silicone rubber, flexible ventricle model. Velocity fields were measured in space and time by means of an image analysis technique: feature tracking. Three series of experiments were performed: one with a top hat inflow velocity profile (schematically resembling physiological conditions), and two with mechanical prosthetic valves of different design, mounted in mitral position-one monoleaflet and the other bileaflet. In each series of runs, two different cardiac outputs have been examined by changing the stroke volume. The flow was investigated in terms of phase averaged velocity field and second order moments of turbulent fluctuations. Results show that the modifications in the transmitral flow change deeply the interaction between the coherent structures generated during the first phase of the diastole and the incoming jet during the second diastolic phase. Top hat inflow gives the coherent structures which are optimal, among the compared cases, for the systolic function. The flow generated by the bileaflet valve preserves most of the beneficial features of the top hat inflow, whereas the monoleaflet valve generates a strong jet which discourages the permanence of large coherent structures at the end of the diastole. Moreover, the average shear rate magnitudes induced by the smoother flow pattern of the case of top hat inflow are nearly halved in comparison with the values measured with the mechanical valves. Finally, analysis of the turbulence statistics shows that the monoleaflet valves yield higher turbulence intensity in comparison with the bileaflet and, with top hat inflow, there is not a complete transition to turbulence.