Mao Wenbin, Li Kewei, Sun Wei
Tissue Mechanics Laboratory, The Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology and Emory University, 206 Technology Enterprise Park, 387 Technology Circle, Atlanta, GA, 30313-2412, USA.
Institute of Biomechanics, Graz University of Technology, Stremayrgasse 16-II, 8010, Graz, Austria.
Cardiovasc Eng Technol. 2016 Dec;7(4):374-388. doi: 10.1007/s13239-016-0285-7. Epub 2016 Nov 14.
Computational modeling of heart valve dynamics incorporating both fluid dynamics and valve structural responses has been challenging. In this study, we developed a novel fully-coupled fluid-structure interaction (FSI) model using smoothed particle hydrodynamics (SPH). A previously developed nonlinear finite element (FE) model of transcatheter aortic valves (TAV) was utilized to couple with SPH to simulate valve leaflet dynamics throughout the entire cardiac cycle. Comparative simulations were performed to investigate the impact of using FE-only models vs. FSI models, as well as an isotropic vs. an anisotropic leaflet material model in TAV simulations. From the results, substantial differences in leaflet kinematics between FE-only and FSI models were observed, and the FSI model could capture the realistic leaflet dynamic deformation due to its more accurate spatial and temporal loading conditions imposed on the leaflets. The stress and the strain distributions were similar between the FE and FSI simulations. However, the peak stresses were different due to the water hammer effect induced by the fluid inertia in the FSI model during the closing phase, which led to 13-28% lower peak stresses in the FE-only model compared to that of the FSI model. The simulation results also indicated that tissue anisotropy had a minor impact on hemodynamics of the valve. However, a lower tissue stiffness in the radial direction of the leaflets could reduce the leaflet peak stress caused by the water hammer effect. It is hoped that the developed FSI models can serve as an effective tool to better assess valve dynamics and optimize next generation TAV designs.
结合流体动力学和瓣膜结构响应来对心脏瓣膜动力学进行计算建模一直具有挑战性。在本研究中，我们使用光滑粒子流体动力学（SPH）开发了一种新型的全耦合流固相互作用（FSI）模型。利用先前开发的经导管主动脉瓣膜（TAV）非线性有限元（FE）模型与SPH耦合，以模拟整个心动周期中的瓣膜小叶动力学。进行了对比模拟，以研究在TAV模拟中使用仅有限元模型与FSI模型的影响，以及各向同性与各向异性小叶材料模型的影响。从结果来看，观察到仅有限元模型和FSI模型之间小叶运动学存在显著差异，并且FSI模型能够捕捉到实际的小叶动态变形，因为它施加在小叶上的空间和时间加载条件更为精确。有限元模拟和FSI模拟之间的应力和应变分布相似。然而，由于FSI模型在关闭阶段流体惯性引起的水击效应，峰值应力有所不同，这导致仅有限元模型的峰值应力比FSI模型低13 - 28%。模拟结果还表明，组织各向异性对瓣膜血液动力学的影响较小。然而，小叶径向方向较低的组织刚度可以降低水击效应引起的小叶峰值应力。希望所开发的FSI模型能够作为一种有效工具，更好地评估瓣膜动力学并优化下一代TAV设计。
