Abstract
Abstract While the current generation of devices for minimally invasive treatment of severe symptomatic aortic valve stenosis is based on xenogenic leaflet-material, artificial polymeric leaflet-structures represent a promising approach for future improvement of heart valve performance. For enhanced long-term success of polymeric leafletstructures, limitations regarding calcification and durability have to be addressed. The objective of the presented study was the development of a constitutive law representing the material properties of artificial polymeric leaflet-structures of transcatheter heart valve prostheses in numerical simulation to assess the in silico leaflet-performance. Mechanical characterization of cast films and nonwoven specimens of a polycarbonate based silicone elastomer were conducted by means of uniaxial tension and planar shear testing, respectively. For validation purposes, experimental data were compared with the results of finite-element analysis (FEA) using different hyperelastic models. Strain energy function for third-order ogden hyperelastic model achieved the best fit of the non-linear stress-strain behavior of the isotropic polymeric material with the experimental data. It was chosen for further FEA of valve leaflet-performance under physiological pressurization to analyze the suitability of various manufacturing processes for polymeric leafletstructures. Therefore a specific leaflet-design with a wall thickness of 400 μm was used. As a result of FEA, time dependent leaflet-deformation, leaflet coaptation surface area (CSA) and leaflet opening area (LOA) of cast and nonwoven leaflet-structures were calculated. While LOA was comparable for cast and nonwoven leaflet-structures, obtained leaflet-dynamics in a cardiac cycle under physiological pressurization demonstrated crucial influence of the manufacturing process. For nonwoven leafletstructures, an enhanced CSA could be demonstrated in comparison to cast structures. FEA using a validated hyperelastic constitutive law represents a useful tool for in silico performance evaluation of polymeric leaflet-structures under physiological loading and proves the suitability of the polymeric artificial leaflet-material for percutaneous heart valve prostheses.
Highlights
The future generation of devices for minimally invasive treatment of aortic valve stenosis will benefit from leafletstructures based on artificial polymeric materials
Experimental determined data of uniaxial tension and planar shear testing were compared with numerical results of Finite-element analysis (FEA) using ABAQUS/Standard 2017 (Dassault Systèmes, Vélizy-Villacoublay, France)
Numerical stress-strain behavior for different hyperelastic models of order N was evaluated with regard to stability and accuracy compared to the test data for cast films and nonwoven specimens, respectively
Summary
The future generation of devices for minimally invasive treatment of aortic valve stenosis will benefit from leafletstructures based on artificial polymeric materials. Crucial improvenents concerning heart valve performance, durability, calcification and shelf life properties represent key aspects of the current research in the field of polymeric leaflet-structures [1,2]. Finite-element analysis (FEA) represents an essential tool for the design development of heart valve leafletstructures. The mechanical behavior and in silico deformation of aortic heart valve leaflets under physiological loading and the influence of various design parameters on its performance has been investigated in structural mechanical FEA, previously [3,4,5]. We developed and validated a hyperelastic constitutive law for polymeric leaflet-structures for FEA. S. Pfensig et al, Development of a constitutive law for numeri-cal simulation of artificial leaflet-structures — 570
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