We develop a fluid-structure interaction (FSI) model of the mitral valve (MV) that uses an anatomically and physiologically realistic description of the MV leaflets and chordae tendineae. Three different chordae models-complex, 'pseudo-fibre' and simplified chordae-are compared to determine how different chordae representations affect the dynamics of the MV. The leaflets and chordae are modelled as fibre-reinforced hyperelastic materials, and FSI is modelled using an immersed boundary-finite element method. The MV model is first verified under static boundary conditions against the commercial finite element software ABAQUS and then used to simulate MV dynamics under physiological pressure conditions. Interesting flow patterns and vortex formulation are observed in all three cases. To quantify the highly complex system behaviour resulting from FSI, an energy budget analysis of the coupled MV FSI model is performed. Results show that the complex and pseudo-fibre chordae models yield good valve closure during systole but that the simplified chordae model leads to poorer leaflet coaptation and an unrealistic bulge in the anterior leaflet belly. An energy budget analysis shows that the MV models with complex and pseudo-fibre chordae have similar energy distribution patterns but the MV model with the simplified chordae consumes more energy, especially during valve closing and opening. We find that the complex chordae and pseudo-fibre chordae have similar impact on the overall MV function but that the simplified chordae representation is less accurate. Because a pseudo-fibre chordal structure is easier to construct and less computationally intensive, it may be a good candidate for modelling MV dynamics or interaction between the MV and heart in patient-specific applications.

中文翻译：

---

关于二尖瓣的腱索结构和动态行为。

我们开发了二尖瓣 (MV) 的流固耦合 (FSI) 模型，该模型使用 MV 小叶和腱索的解剖学和生理学真实描述。比较三种不同的腱索模型（复杂的、“伪纤维”和简化的腱索模型），以确定不同的腱索表示如何影响 MV 的动态。小叶和腱索被建模为纤维增强超弹性材料，并且 FSI 使用浸入式边界有限元方法进行建模。MV模型首先在商业有限元软件ABAQUS的静态边界条件下进行验证，然后用于模拟生理压力条件下的MV动力学。在所有三种情况下都观察到有趣的流动模式和涡流形成。为了量化 FSI 产生的高度复杂的系统行为，对耦合的 MV FSI 模型进行了能量预算分析。结果表明，复杂和伪纤维腱索模型在收缩期间产生良好的瓣膜闭合，但简化的腱索模型导致小叶接合较差，并且前叶腹部出现不切实际的凸起。能量预算分析表明，具有复杂腱索和伪纤维腱索的 MV 模型具有相似的能量分布模式，但具有简化腱索的 MV 模型消耗更多能量，特别是在阀门关闭和打开期间。我们发现复杂腱索和伪纤维腱索对整体 MV 功能有类似的影响，但简化的腱索表示不太准确。由于伪纤维弦结构更容易构建且计算强度较小，因此它可能是在患者特定应用中对 MV 动力学或 MV 与心脏之间的相互作用进行建模的良好候选者。