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A computational human mitral valve (MV) model under physiological pressure loading is developed using a hybrid finite element immersed boundary method, which incorporates experimentally-based constitutive laws in a three-dimensional fluid-structure interaction framework. A transversely isotropic material constitutive model is used to characterize the mechanical behaviour of the MV tissue based on recent mechanical tests of healthy human mitral leaflets. Our results show good agreement, in terms of the flow rate and the closing and opening configurations, with measurements from in vivo magnetic resonance images. The stresses in the anterior leaflet are found to be higher than those in the posterior leaflet and are concentrated around the annulus trigons and the belly of the leaflet. The results also show that the chordae play an important role in providing a secondary orifice for the flow when the valve opens. Although there are some discrepancies to be overcome in future work, our simulations show that the developed computational model is promising in mimicking the in vivo MV dynamics and providing important information that are not obtainable by in vivo measurements. © 2014 The Authors. International Journal for Numerical Methods in Biomedical Engineering published by John Wiley & Sons Ltd.

Dysfunction of mitral valve causes morbidity and premature mortality and remains a leading medical problem worldwide. Computational modelling aims to understand the biomechanics of human mitral valve and could lead to the development of new treatment, prevention and diagnosis of mitral valve diseases. Compared with the aortic valve, the mitral valve has been much less studied owing to its highly complex structure and strong interaction with the blood flow and the ventricles. However, the interest in mitral valve modelling is growing, and the sophistication level is increasing with the advanced development of computational technology and imaging tools. This review summarises the state‐of‐the‐art modelling of the mitral valve, including static and dynamics models, models with fluid‐structure interaction, and models with the left ventricle interaction. Challenges and future directions are also discussed.

In this paper, three different constitutive laws for mitral leaflets and two laws for chordae tendineae are selected to study their effects on mitral valve dynamics with fluid-structure interaction. We first fit these three mitral leaflet constitutive laws and two chordae tendineae laws with experimental data. The fluid-structure interaction is implemented in an immersed boundary framework with finite element extension for solid, that is the hybrid immersed boundary/finite element(IB/FE) method. We specifically compare the fluid-structure results of different constitutive laws since fluid-structure interaction is the physiological loading environment. This allows us to look at the peak jet velocity, the closure regurgitation volume, and the orifice area. Our numerical results show that different constitutive laws can affect mitral valve dynamics, such as the transvalvular flow rate, closure regurgitation and the orifice area, while the differences in fiber strain and stress are insignificant because all leaflet constitutive laws are fitted to the same set of experimental data. In addition, when an exponential constitutive law of chordae tendineae is used, a lower closure regurgitation flow is observed compared to that of a linear material model. In conclusion, combining numerical dynamic simulations and static experimental tests, we are able to identify suitable constitutive laws for dynamic behaviour of mitral leaflets and chordae under physiological conditions. Because mitral valve (MV) has a very complex tissue structure, any change or loss of its structure will lead to valve diseases. In recent years, valve disease have become one of the major cardiovascular diseases 1 . It is estimated that 850000 patients will be treated with valve replacement by 2050 2 . It is being recognized that the mathematical modelling and numerical simulation of the interaction between MV and blood flow are of great value and significance to deepen our understanding of valve-related diseases and treatment 3-6 .Since early of the 19th century, researchers began to study MV geometric features and have made great progress. Different types of MV model have been developed for simulating MV dynamics, such as symmetrical geometries 7-10 , and idealized parametric models 11 . The rapid development of non-invasive clinical imaging technologies, such as ultrasound, computed tomography and magnetic resonance, have allowed the construction of patient-specific MV model. For example, Lim et al. 12 built an asymmetric MV model with three-dimensional (3-D) dynamic boundaries and non-linear pressure loadings over the whole cardiac cycle based on in-vivo experimental data. Wenk et al. 13 developed a finite element (FE) model consisting of the left ventricle, the MV leaflet and chordae tendineae using magnetic resonance images of sheep. Wang et al. 14 reconstructed a patient-specific MV geometry using a multi-slice CT scan with detailed leaflet thickness and chordae tendineae structure. Ma et al. 15 and Gao et al. 16 developed MV models based on magne...

Abstract. We present an integrated model of mitral valve coupled with the left ventricle. The model is derived from clinical images and takes into account of the important valvular features, left ventricle contraction, nonlinear soft tissue mechanics, fluid structure interaction, and the MV-LV interaction. This model is compared with a corresponding mitral-tube model, and differences in the results are discussed. Although the model is a step closer towards simulating physiological realistic situation, further work is required to ensure that the highly complex valvular-ventricular interaction, and the fluid-structure interaction, can be reliably represented.

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Decellularization method based on trypsin-digestion is widely used to construct small diameter vascular grafts. However, this method will reduce the opening angle of the blood vessel and result in the reduction of residual stress. Residual stress reduced has an adverse effect on the compliance and permeability of small diameter vascular grafts. To improve the situation, acellular blood vessels were treated with glutaraldehyde and photooxidation crosslinking respectively, and the changes of opening angle, circumferential residual strain of native blood vessels, decellularized arteries and crosslinked blood vessels were measured by means of histological examination, scanning electron microscopy (SEM) and transmission electron microscopy (TEM) in this study. The opening angle of decellularized arteries significantly restored after photooxidation crosslinking (P = 0.0216), while that of glutaraldehyde crosslinking blood vessels reduced. The elastic fibers inside the blood vessels became densely rearranged after photooxidation crosslinking. The results of finite element simulation showed that the residual stress increased with the increase of opening angle. In this study, we found at the first time that photooxidation crosslinking method could significantly increase the residual stress of decellularized vessels, which provides biomechanical support for the development of new biomaterials of vascular grafts.