A hybrid phenomenological finite element model of transcatheter aortic valve leaflet behaviour under non-circular annular deployment: in vitro validation and biomechanical insights

Figures

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  Fig. 1. Benchmark finite element model of a cantilever beam sample of bovine pericardium under boundary conditions mimicking the real experimental test conditions

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  Fig. 2. Scheme of application of a neural network to obtain the response surface

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  Fig. 3. Response surface obtained from the inverse analysis. The minimum RMSE is highlighted in red. Left: 2D colour representation, where colour indicates the error magnitude. Right: 3D representation of the same response surface, where the error magnitude is represented along the vertical axis

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  Fig. 4. Comparison between real deformation and the deformation obtained from simulation for the cantilever bending model that best represents the behaviour of the material. The x- and y-axis scales are not identical, following the representation format used in Murdock et al. (Murdock et al. 2018), in order to facilitate comparison between results

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  Fig. 5. Comparison between the real ALLEGRA transcatheter aortic valve and the corresponding finite element model developed in this study. Two of the valve gold markers are visible in the real device picture with their characteristic gold colour, whereas the corresponding markers are represented in blue in the FEM model

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  Fig. 6. Transformation of the leaflet geometry from its initial configuration: flat pericardial tissue after cutting of the leaflet pattern, displacement of the elliptical border from the planar configuration to the final three-dimensional geometry connected to the skirt, and final mesh smoothing and refinement

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  Fig. 7. Time-varying pressure for human cardiac cycle: a Left ventricular and aortic pressure b transvalvular pressure. From Shier et al. (1996)

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  Fig. 8. First step of the simulation: radial compression of the valve using a cylindrical surface to fully introduce it into the elliptical geometry

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  Fig. 9. Second step of the simulation: adaptation of the valve to the eliptical geometry

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  Fig. 10. Comparison between the FE model (top row) and the in vitro test (bottom row) for E=1E=1: a valve closure during diastole showing the pinwheeling effect; b valve opening during systole with full leaflet expansion

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  Fig. 11. Commissural alignment for the elliptical annulus (E=1.5E=1.5). a FE model with major axis aligned with leaflet commissures (90\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$^\circ$$\end{document}∘ orientation); b In vitro setup with same alignment; c FE model with major axis perpendicular to commissures (0\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$^\circ$$\end{document}∘ orientation)

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  Fig. 12. Comparison between the FE model and the in vitro test for E=1.5E=1.5 (90º orientation): a–d leaflet opening during systole; d–f leaflet closure during diastole