A functionally graded material model for the transmural stress distribution of the aortic valve leaflet
A functionally graded material model for the transmural stress distribution of the aortic valve leaflet
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DOI：
10.1016/j.jbiomech.2017.01.039
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发表时间：
2017-03-21
影响因子：
2.4
通讯作者：
Sacks, Michael S.
中科院分区：
文献类型：
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作者：
Rego, Bruno V.;Sacks, Michael S.
心脏瓣膜小叶内结构和应力的异质性对其功能生理学具有重要意义，因为它们影响组织成分如何在病理和非病理性（如运动、妊娠）心功能改变时进行重塑。事实上，已知瓣膜间质细胞（vic）以特定于其局部微机械环境的方式合成和降解小叶细胞外基质（ECM）成分。因此，量化ECM结构和应力的局部变化对于了解内稳态瓣膜维持以及建立疾病进展和术后结果的预测模型是必要的。在主动脉瓣（AV）中，通过将小叶建模为连续但机械上不同的层的复合物，先前已经研究了跨壁应力变化。基于先前关于这些层粘合性质的发现（Buchanan和Sacks， BMMB, 2014），我们通过将小叶视为功能梯度材料（FGM），其性质随厚度连续变化，开发了更广义的结构本构模型。我们使用高分辨率形态学测量来建立FGM模型，结果表明，成分和纤维结构随着AV小叶的厚度逐渐变化。为了验证，我们拟合模型对整个传单和个别层力学响应的广泛数据库。FGM模型预测了舒张末期小叶层之间和内部的大应力变化，低胶原蛋白区域承受显著的径向应力。这些新结果表明，持续变化的房室小叶结构在瓣膜功能和组织稳态方面具有重要作用。(C) 2017 Elsevier Ltd.版权所有。
Heterogeneities in structure and stress within heart valve leaflets are of significant concern to their functional physiology, as they affect how the tissue constituents remodel in response to pathological and non pathological (e.g. exercise, pregnancy) alterations in cardiac function. Indeed, valve interstitial cells (VICs) are known to synthesize and degrade leaflet extracellular matrix (ECM) components in a manner specific to their local micromechanical environment. Quantifying local variations in ECM structure and stress is thus necessary to understand homeostatic valve maintenance as well as to develop predictive models of disease progression and post-surgical outcomes. In the aortic valve (AV), transmural variations in stress have previously been investigated by modeling the leaflet as a composite of contiguous but mechanically distinct layers. Based on previous findings about the bonded nature of these layers (Buchanan and Sacks, BMMB, 2014), we developed a more generalized structural constitutive model by treating the leaflet as a functionally graded material (FGM), whose properties vary continuously over the thickness. We informed the FGM model using high-resolution morphological measurements, which demonstrated that the composition and fiber structure change gradually over the thickness of the AV leaflet. For validation, we fit the model against an extensive database of whole-leaflet and individual layer mechanical responses. The FGM model predicted large stress variations both between and within the leaflet layers at end-diastole, with low-collagen regions bearing significant radial stress. These novel results suggest that the continually varying structure of the AV leaflet has an important purpose with regard to valve function and tissue homeostasis. (C) 2017 Elsevier Ltd. All rights reserved.