Background: Tricuspid valve chordae tendineae play a vital role in our cardiovascular system. They function as “parachute cords” to the tricuspid leaflets to prevent prolapse during systole. However, in contrast to the tricuspid annulus and leaflets, the tricuspid chordae tendineae have received little attention. Few previous studies have described their mechanics and their structure-function relationship. Objective: In this study, we aimed to quantify the mechanics of tricuspid chordae tendineae based on their leaflet of origin, insertion site, and size. Methods: Specifically, we uniaxially stretched 53 tricuspid chordae tendineae from sheep and recorded their stress-strain behavior. We also analyzed the microstructure of the tricuspid chordae tendineae based on two-photon microscopy and histology. Finally, we compared eight different hyperelastic constitutive models and their ability to fit our data. Results: We found that tricuspid chordae tendineae are highly organized collageneous tissues, which are populated with cells throughout their thickness. In uniaxial stretching, this microstructure causes the classic J-shaped nonlinear stress-strain response known from other collageneous tissues. We found differences in stiffness between tricuspid chordae tendineae from the anterior, posterior, or septal leaflets only at small strains. Similarly, we found significant differences based on their insertion site or size also only at small strains. Of the models we fit to our data, we recommend the Ogden two-parameter model. This model fit the data excellently and required a minimal number of parameters. For future use, we identified and reported the Ogden material parameters for an average data set. Conclusion: The data presented in this study help to explain the mechanics and structure-function relationship of tricuspid chordae tendineae and provide a model recommendation (with parameters) for use in computational simulations of the tricuspid valve.

中文翻译：

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三尖瓣腱索力学：插入位点、传单和特定尺寸的分析和本构建模

背景：三尖瓣腱索在我们的心血管系统中起着至关重要的作用。它们充当三尖瓣小叶的“降落伞绳”，以防止收缩期间脱垂。然而，与三尖瓣环和小叶相比，三尖瓣腱索很少受到关注。以前的研究很少描述它们的力学和它们的结构-功能关系。目的：在这项研究中，我们旨在根据三尖瓣腱索的起源、插入部位和大小来量化它们的力学。方法：具体而言，我们对绵羊的 53 条三尖瓣腱索进行单轴拉伸并记录其应力应变行为。我们还基于双光子显微镜和组织学分析了三尖瓣腱索的微观结构。最后，我们比较了八种不同的超弹性本构模型及其拟合数据的能力。结果：我们发现三尖瓣腱索是高度有组织的胶原组织，其整个厚度都充满了细胞。在单轴拉伸中，这种微结构会导致其他胶原组织中已知的经典 J 形非线性应力应变响应。我们发现来自前、后或间隔小叶的三尖瓣腱索之间的刚度差异仅在小应变下。同样，我们发现基于它们的插入位点或大小的显着差异也仅在小菌株中。在我们拟合数据的模型中，我们推荐 Ogden 两参数模型。该模型非常适合数据，并且需要最少的参数。为了将来使用，我们确定并报告了平均数据集的 Ogden 材料参数。结论：本研究中提供的数据有助于解释三尖瓣腱索的力学和结构 - 功能关系，并提供用于三尖瓣计算模拟的模型推荐（带参数）。