Jun Brian H, Saikrishnan Neelakantan, Arjunon Sivakkumar, Yun B Min, Yoganathan Ajit P
J Biomech Eng. 2014 Sep;136(9):091008. doi: 10.1115/1.4027935.
The hinge regions of the bileaflet mechanical heart valve (BMHV) can cause blood element damage due to nonphysiological shear stress levels and regions of flow stasis. Recently, a micro particle image velocimetry (μPIV) system was developed to study whole flow fields within BMHV hinge regions with enhanced spatial resolution under steady leakage flow conditions. However, global velocity maps under pulsatile conditions are still necessary to fully understand the blood damage potential of these valves. The current study hypothesized that the hinge gap width will affect flow fields in the hinge region. Accordingly, the blood damage potential of three St. Jude Medical (SJM) BMHVs with different hinge gap widths was investigated under pulsatile flow conditions, using a μPIV system. The results demonstrated that the hinge gap width had a significant influence during the leakage flow phase in terms of washout and shear stress characteristics. During the leakage flow, the largest hinge gap generated the highest Reynolds shear stress (RSS) magnitudes (~1000 N/m²) among the three valves at the ventricular side of the hinge. At this location, all three valves indicated viscous shear stresses (VSS) greater than 30 N/m². The smallest hinge gap exhibited the lowest level of shear stress values, but had the poorest washout flow characteristics among the three valves, demonstrating propensity for flow stasis and associated activated platelet accumulation potential. The results from this study indicate that the hinge is a critical component of the BMHV design, which needs to be optimized to find the appropriate balance between reduction in fluid shear stresses and enhanced washout during leakage flow, to ensure minimal thrombotic complications.
双叶机械心脏瓣膜（BMHV）的铰链区域可因非生理性剪切应力水平和血流淤滞区域而导致血液成分受损。最近，开发了一种微观粒子图像测速（μPIV）系统，用于在稳定泄漏流条件下以更高的空间分辨率研究BMHV铰链区域内的整个流场。然而，脉动条件下的整体速度图对于全面了解这些瓣膜的血液损伤潜力仍然是必要的。当前研究假设铰链间隙宽度会影响铰链区域的流场。因此，使用μPIV系统在脉动流条件下研究了三种具有不同铰链间隙宽度的圣犹达医疗（SJM）BMHV的血液损伤潜力。结果表明，在泄漏流阶段，铰链间隙宽度在冲洗和剪切应力特性方面有显著影响。在泄漏流期间，最大的铰链间隙在铰链心室侧产生了三种瓣膜中最高的雷诺剪切应力（RSS）幅值（约1000 N/m²）。在此位置，所有三种瓣膜的粘性剪切应力（VSS）均大于30 N/m²。最小的铰链间隙表现出最低水平的剪切应力值，但在三种瓣膜中冲洗流特性最差，表明有血流淤滞倾向以及相关的活化血小板积聚潜力。本研究结果表明，铰链是BMHV设计的关键部件，需要进行优化，以在降低流体剪切应力和增强泄漏流期间的冲洗之间找到适当平衡，以确保血栓形成并发症最少。
