分层血管对心脏瓣膜流固耦合的影响

Effect of stratified vessels on fluid-solid interaction of heart valves

背景:心脏瓣膜病的治疗手段主要为心脏瓣膜置换,人工心脏瓣膜的设计和性能优化是目前研究者和业界研究与探索的主要方向。数值分析和实验的方式是分析人工心脏瓣膜力学性能的主要方法。利用有限元技术分析瓣膜力学性能,揭示瓣膜在体内运行环境下的微观受力情况,可为人工心脏瓣膜的设计和性能优化提供更加准确的数据。目的:建立更接近人体实际情况的血管模型,探究分层血管对主动脉瓣变形特点和应力分布的影响,为进一步改进人工心瓣的设计提供力学支持。方法:建立包括主动脉瓣、血管壁和血液的有限元几何模型和数学模型,其中血管壁为分层血管,探讨血管分层特性对主动脉瓣流固耦合变形及应力大小的影响,验证分层血管壁对实验的重要性。结果与结论:①瓣膜变形主要发生在瓣叶处,动脉壁没有明显的变形,瓣叶自由边汇合处变形最大,从瓣叶自由边到缝合边变形量呈梯度降低;②整个心脏瓣膜模型的等效应力最大值位于动脉壁外壁(瓣叶与动脉壁缝合点附近),动脉壁内外壁受力差异大,内壁相较于外壁等效应力值小很多,壁面之间存在应力不连续性;③瓣叶最大等效应力在瓣叶与动脉壁的缝合边处。与以往未考虑血管分层特性的研究结果相比,瓣叶最大等效应力值更接近人体二尖瓣叶的离体失效应力。

BACKGROUND: The main treatment for valvular heart disease is heart valve replacement. The design and performance optimization of artificial heart valves are currently the areas of research. Numerical analysis and experimental methods are major keys to analyzing the mechanical properties of artificial heart valves. Analyzing the mechanical properties of the valves by finite element method and displaying the mciro-stress of the valves in vivo provide more accurate data for the design and performance optimization of artificial heart valve. OBJECTIVE: To establish a more realistic vascular model and investigate the effects of stratified vessels on the deformation characteristics and stress distribution of aortic valves, providing theoretical mechanical data for further improving the design of artificial heart valve. METHODS: Finite element geometric models and mathematical models including aortic valve, vessel wall and blood were established, in which the vessel wall was stratified. The effects of stratification characteristics on the fluid-solid interaction deformation and stress of the aortic valve were investigated to verify the importance of the stratified vessel wall. RESULTS AND CONCLUSION: Valve deformation mainly occurred in the leaflets, the arterial wall had no obvious deformation, the highest level of free deformation was observed at the leaflet free edge. The deformation from the free edge of the leaflet to the suture edge showed a gradient decrease tendency. The maximum equivalent stress of the whole heart valve model was located on the outer arterial wall (near the suture point of the valve leaflet and the arterial wall). The inner and outer arterial walls were greatly different in force. The equivalent stress value of the inner arterial wall was much smaller than that of the outer arterial wall. The stress between inner and outer arterial walls was not continuous. The maximum equivalent stress of the leaflets was at the suture edge of the leaflets and the arterial wall. Compared with the previous studies that did not consider the stratification characteristics of the arterial wall, the maximum equivalent stress value of the leaflets was closer to the ex vivo failure stress of the human mitral valve leaflets.