Valvular heart diseases are complex disorders, varying in pathophysiological mechanism and affected valve components. Understanding the effects of these diseases on valve functionality requires a thorough characterization of the mechanics and structure of the healthy heart valves. In this study, we performed biaxial mechanical experiments with extensive testing protocols to examine the mechanical behaviors of the mitral valve and tricuspid valve leaflets. We also investigated the effect of loading rate, testing temperatures, species (porcine versus ovine hearts), and age (juvenile vs adult ovine hearts) on the mechanical responses of the leaflet tissues. In addition, we evaluated the structure of chordae tendineae within each valve and performed histological analysis on each atrioventricular leaflet. We found all tissues displayed a characteristic nonlinear anisotropic mechanical response, with radial stretches on average 30.7% higher than circumferential stretches under equibiaxial physiological loading. Tissue mechanical responses showed consistent mechanical stiffening in response to increased loading rate and minor temperature dependence in all five atrioventricular heart valve leaflets. Moreover, our anatomical study revealed similar chordae quantities in the porcine mitral (30.5 ± 1.43 chords) and tricuspid valves (35.3 ± 2.45 chords) but significantly more chordae in the porcine than the ovine valves (p < 0.010). Our histological analyses quantified the relative thicknesses of the four distinct morphological layers in each leaflet. This study provides a comprehensive database of the mechanics and structure of the atrioventricular valves, which will be beneficial to development of subject-specific atrioventricular valve constitutive models and toward multi-scale biomechanical investigations of heart valve function to improve valvular disease treatments.

瓣膜性心脏病是复杂的疾病，其病理生理机制和受影响的瓣膜成分各不相同。了解这些疾病对瓣膜功能的影响需要对健康心脏瓣膜的力学和结构进行全面表征。在这项研究中，我们通过广泛的测试协议进行了双轴机械实验，以检查二尖瓣和三尖瓣小叶的机械行为。我们还研究了加载速率、测试温度、物种（猪心与绵羊心）和年龄（幼年绵羊心与成年绵羊心）对小叶组织机械反应的影响。此外，我们评估了每个瓣膜内腱索的结构并对每个房室小叶进行了组织学分析。我们发现所有组织都表现出特征性的非线性各向异性机械响应，在等双轴生理负荷下，径向拉伸比周向拉伸平均高 30.7%。组织机械反应显示一致的机械硬化响应所有五个房室心脏瓣膜小叶中增加的负荷率和较小的温度依赖性。此外，我们的解剖学研究表明，猪二尖瓣 (30.5 ± 1.43 弦) 和三尖瓣 (35.3 ± 2.45 弦) 的腱索数量相似，但猪的腱索明显多于绵羊瓣膜 (p < 0.010)。我们的组织学分析量化了每个小叶中四个不同形态层的相对厚度。