Computational modeling of heart valve dynamics incorporating both fluid dynamics and valve structural responses has been challenging. In this study, we developed a novel fully-coupled fluid-structure interaction (FSI) model using smoothed particle hydrodynamics (SPH). A previously developed nonlinear finite element (FE) model of transcatheter aortic valves (TAV) was utilized to couple with SPH to simulate valve leaflet dynamics throughout the entire cardiac cycle. Comparative simulations were performed to investigate the impact of using FE-only models vs. FSI models, as well as an isotropic vs. an anisotropic leaflet material model in TAV simulations. From the results, substantial differences in leaflet kinematics between FE-only and FSI models were observed, and the FSI model could capture the realistic leaflet dynamic deformation due to its more accurate spatial and temporal loading conditions imposed on the leaflets. The stress and the strain distributions were similar between the FE and FSI simulations. However, the peak stresses were different due to the water hammer effect induced by the fluid inertia in the FSI model during the closing phase, which led to 13-28% lower peak stresses in the FE-only model compared to that of the FSI model. The simulation results also indicated that tissue anisotropy had a minor impact on hemodynamics of the valve. However, a lower tissue stiffness in the radial direction of the leaflets could reduce the leaflet peak stress caused by the water hammer effect. It is hoped that the developed FSI models can serve as an effective tool to better assess valve dynamics and optimize next generation TAV designs.

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Fluid–Structure Interaction Study of Transcatheter Aortic Valve Dynamics Using Smoothed Particle Hydrodynamics

Quantification and comparison of the mechanical properties of four human cardiac valves

Structural analysis of the natural aortic valve in dynamics: From unpressurized to physiologically loaded

Microfabricated poly(glycerol sebacate) (PGS) scaffolds may be applicable to tissue engineering heart valve leaflets by virtue of their controllable microstructure, stiffness, and elasticity. In this study, PGS scaffolds were computationally designed and microfabricated by laser ablation to match the anisotropy and peak tangent moduli of native bovine aortic heart valve leaflets. Finite element simulations predicted PGS curing conditions, scaffold pore shape, and strut width capable of matching the scaffold effective stiffnesses to the leaflet peak tangent moduli. On the basis of simulation predicted effective stiffnesses of 1.041 and 0.208 MPa for the scaffold preferred (PD) and orthogonal, cross-preferred (XD) material directions, scaffolds with diamond-shaped pores were microfabricated by laser ablation of PGS cured 12 h at 160°C. Effective stiffnesses measured for the scaffold PD (0.83 ± 0.13 MPa) and XD (0.21 ± 0.03 MPa) were similar to both predicted values and peak tangent moduli measured for bovine aortic valve leaflets in the circumferential (1.00 ± 0.16 MPa) and radial (0.26 ± 0.03 MPa) directions. Scaffolds cultivated with fibroblasts for 3 weeks accumulated collagen (736 ± 193 μg/g wet weight) and DNA (17 ± 4 μg/g wet weight). This study provides a basis for the computational design of biomimetic microfabricated PGS scaffolds for tissue-engineered heart valves.

Laser microfabricated poly(glycerol sebacate) scaffolds for heart valve tissue engineering.

Introduction: Replacement with a prosthetic device remains a major treatment option for the patients suffering from heart valve disease, with prevalence growing resulting from an ageing population....

/pdf/computational-methods-for-the-aortic-heart-valve-and-its-2bmmppcwao.pdf

Computational methods for the aortic heart valve and its replacements.

This work was concerned with the numerical simulation of the behaviour of aortic valves whose material can be modelled as non-linear elastic anisotropic Linear elastic models for the valve leaflets with parameters used in previous studies were compared with hyperelastic models, incorporating leaflet anisotropy with pronounced stiffness in the circumferential direction through a transverse isotropic model The parameters for the hyperelastic models were obtained from fits to results of orthogonal uniaxial tensile tests on porcine aortic valve leaflets The computational results indicated the significant impact of transverse isotropy and hyperelastic effects on leaflet mechanics; in particular, increased coaptation with peak values of stress and strain in the elastic limit The alignment of maximum principal stresses in all models follows approximately the coarse collagen fibre distribution found in aortic valve leaflets The non-linear elastic leaflets also demonstrated more evenly distributed stress and strain which appears relevant to long-term scaffold stability and mechanotransduction

T M Koch

Papers

Aortic valve leaflet mechanical properties facilitate diastolic valve function