Dumont Kris, Vierendeels Jan, Kaminsky Rado, van Nooten Guido, Verdonck Pascal, Bluestein Danny
Cardiovascular Mechanics and Biofluid Dynamics Research Unit, IBiTech, Ghent University, Belgium.
J Biomech Eng. 2007 Aug;129(4):558-65. doi: 10.1115/1.2746378.
The hemodynamic and the thrombogenic performance of two commercially available bileaflet mechanical heart valves (MHVs)--the ATS Open Pivot Valve (ATS) and the St. Jude Regent Valve (SJM), was compared using a state of the art computational fluid dynamics-fluid structure interaction (CFD-FSI) methodology. A transient simulation of the ATS and SJM valves was conducted in a three-dimensional model geometry of a straight conduit with sudden expansion distal the valves, including the valve housing and detailed hinge geometry. An aortic flow waveform (60 beats/min, cardiac output 4 l/min) was applied at the inlet. The FSI formulation utilized a fully implicit coupling procedure using a separate solver for the fluid problem (FLUENT) and for the structural problem. Valve leaflet excursion and pressure differences were calculated, as well as shear stress on the leaflets and accumulated shear stress on particles released during both forward and backward flow phases through the open and closed valve, respectively. In contrast to the SJM, the ATS valve opened to less than maximal opening angle. Nevertheless, maximal and mean pressure gradients and velocity patterns through the valve orifices were comparable. Platelet stress accumulation during forward flow indicated that no platelets experienced a stress accumulation higher than 35 dyne x s/cm2, the threshold for platelet activation (Hellums criterion). However, during the regurgitation flow phase, 0.81% of the platelets in the SJM valve experienced a stress accumulation higher than 35 dyne x s/cm2, compared with 0.63% for the ATS valve. The numerical results indicate that the designs of the ATS and SJM valves, which differ mostly in their hinge mechanism, lead to different potential for platelet activation, especially during the regurgitation phase. This numerical methodology can be used to assess the effects of design parameters on the flow induced thrombogenic potential of blood recirculating devices.
使用先进的计算流体动力学-流固耦合（CFD-FSI）方法，比较了两种市售双叶机械心脏瓣膜（MHV）——ATS开放枢轴瓣膜（ATS）和圣犹达Regent瓣膜（SJM）的血流动力学和血栓形成性能。在瓣膜远端有突然扩张的直管三维模型几何结构中，对ATS和SJM瓣膜进行了瞬态模拟，包括瓣膜外壳和详细的铰链几何结构。在入口处施加主动脉血流波形（60次/分钟，心输出量4升/分钟）。FSI公式采用了完全隐式耦合程序，使用单独的求解器分别求解流体问题（FLUENT）和结构问题。计算了瓣膜小叶偏移和压力差，以及小叶上的剪应力和在正向和反向流动阶段通过打开和关闭的瓣膜释放的颗粒上的累积剪应力。与SJM不同，ATS瓣膜打开到小于最大开口角度。然而，通过瓣膜孔的最大和平均压力梯度以及速度模式是可比的。正向流动期间血小板应力累积表明，没有血小板经历高于35达因·秒/平方厘米的应力累积，这是血小板激活的阈值（赫勒姆斯标准）。然而，在反流流动阶段，SJM瓣膜中0.81%的血小板经历了高于35达因·秒/平方厘米的应力累积，而ATS瓣膜为0.63%。数值结果表明，ATS和SJM瓣膜的设计主要在其铰链机制上有所不同，导致血小板激活的潜力不同，尤其是在反流阶段。这种数值方法可用于评估设计参数对血液再循环装置的流动诱导血栓形成潜力的影响。
