Feng Z, Umezu M, Fujimoto T, Tsukahara T, Nurishi M, Kawaguchi D
Department of Mechanical Engineering, Waseda University, Shinjuku, Tokyo, Japan.
Artif Organs. 2000 May;24(5):346-54. doi: 10.1046/j.1525-1594.2000.06498.x.
The non-fully open phenomenon of the advancing standard medical bileaflet heart valves (the ATS valve) are frequently observed in clinical cases, even though there is no problem with their hemodynamic function. The movement of the leaflets was affected easily by the transvalvular flow because of the unique open pivot design of the ATS valve. In this paper, a comparative in vitro hydrodynamic test was conducted among 3 different types of bileaflet valves, and the effect of different shapes of downstream conduits, which induce different transvalvular flow, on hydrodynamic performance was studied. Three bileaflet valves, the ATS valve, CarboMedics valve (CM), and St. Jude Medical valve (SJM), with an annulus diameter of 29 mm for the mitral position were chosen throughout our experiments. First, pressure drops across the valves under steady flow were measured. Then, the valves were tested at the mitral position with our pneumatically driven pulsatile pump. In this pulsatile flow study, 2 different conduits (straight shape and abrupt enlargement shape) were in turn incorporated at the downstream portion of the mitral valve. A high-speed video camera was employed to observe leaflet movements. In a steady-flow test, the ATS and the SJM produced the same pressure drop, but the CM recorded a higher value. In the pulsatile study, it was observed that the ATS leaflets did not open fully in the mitral position when the downstream conduit with an abrupt enlargement shape was incorporated. However, the CM and the SJM always indicated a fully open movement regardless of the shape of downstream conduits. When the straight downstream conduit was incorporated, the ATS produced a similar pressure drop to that of the SJM, which coincided with the steady test results. When the enlargement conduit was incorporated, however, the ATS presented the lowest pressure drop despite the non-fully open movement. The conduit shape at the valve downstream had a significant influence on the closing volume. These findings indicate that the conduit shape at the valve outlet can affect the hydrodynamic characteristics of bileaflet valves.
先进的标准双叶心脏瓣膜（ATS瓣膜）的非完全开放现象在临床病例中经常出现，尽管其血流动力学功能没有问题。由于ATS瓣膜独特的开放枢轴设计，瓣叶运动很容易受到跨瓣血流的影响。本文对3种不同类型的双叶瓣膜进行了体外流体动力学对比试验，研究了不同形状的下游管道（会导致不同的跨瓣血流）对流体动力学性能的影响。在我们所有的实验中，选用了三种二尖瓣位置瓣环直径为29mm的双叶瓣膜，即ATS瓣膜、卡博美迪克斯瓣膜（CM）和圣犹达医疗瓣膜（SJM）。首先，测量了稳定流情况下瓣膜两端的压力降。然后，使用我们的气动搏动泵在二尖瓣位置对瓣膜进行测试。在这个搏动流研究中，二尖瓣下游部分依次接入2种不同的管道（直管形状和突然扩大形状）。使用高速摄像机观察瓣叶运动。在稳定流试验中，ATS瓣膜和SJM瓣膜产生的压力降相同，但CM瓣膜记录的压力降值更高。在搏动研究中，观察到当接入下游管道为突然扩大形状时，ATS瓣膜在二尖瓣位置的瓣叶没有完全打开。然而，CM瓣膜和SJM瓣膜无论下游管道形状如何，总是呈现完全打开的运动状态。当接入直管下游管道时，ATS瓣膜产生的压力降与SJM瓣膜相似，这与稳定试验结果一致。然而，当接入扩大管道时，尽管ATS瓣膜的瓣叶没有完全打开，但其压力降却是最低的。瓣膜下游的管道形状对关闭容积有显著影响。这些发现表明，瓣膜出口处的管道形状会影响双叶瓣膜的流体动力学特性。
