Simulation of a mitral valve stent

  Simulation of a Stent Design with Ansys. Figure 1: Simulation of a Stent Design with Ansys.

Background

Transcatheter Mitral Valve Replacement is a new treatment option for risk patients with a mitral valve disease. A new transcatheter mitral valve prosthesis is developed by the connection of a complex stent frame with special polymeric valve leaflets. The frame design, as well as the in-silico and in-vitro tests are performed at the CVE. Factors like material, production and implantation have to be considered in particular for the development of the stent frame. The material Nitinol is predominantly used for the frame. Nitinol stands out by a high biocompatibility, its hyper elasticity and shape memory effect. During the production the frame is at first lasercut out of a tube and afterwards progressively expanded under defined thermal conditions. Shortly before the implantation the complete prosthesis is crimped (radially compressed) by the doctor on a diameter, which depends on the chosen access. The production and implantation condition has to be considered in the design development. By the aimed use of simulation methods (FEM – Finite Element Methode) cost-intensive iteration loops within the design development can be reduced significantly and an optimized product can be developed.

Project objective

Within the PolyValve project, inter alia, a modified stentdesign for a polymeric prosthesis in the mitral valve position is designed. By an exact analysis of conditions of the production, implantation and anatomy a first concept for a transcatheter mitral valve stent framework was developed. It is now optimized in regard to its functionality. In order to guarantee a production oriented design, two fundamental states of a lasercut Nitnol stent, the expanded und crimped shape, are simulated. Therefore the methodology of the simulation is analyzed, so that results can be used for the development of other Nitinol stents and development costs and time can be reduced.

Methodology

By the simulation of the production and implantation processes, it is possible to find weaknesses of the geometry and improve them already during the design process. The simulation methodology of the expansion and crimp procedures is refined regarding to stability and computing power. Therefore various boundary conditions, contact and meshing possibilities, as well as methods are studied, tested and evaluated. The Nitinol material model is optimized and by means of sensitivity analysis validated. Furthermore a comparison between market leading simulation programs is performed for the numerical analysis of the mechanical properties.

 
Funding: This research project is funded by the INTERREG Program V-A Euregio Maas-Rheine of the European Union (Grant Number 2016/98602)