Simulation that goes to the heart

The company ADMEDES Schüssler is a leading global supplier of finished, self-expanding nitinol implants. In order to accurately predict the interaction between the stent and the heart valve during a pulse, a simulation model had to be developed that accurately reflects the transient processes between fluid (blood) and structure (stent network). In addition, it should be possible to make statements about the effects of continuous operation on the lifetime of the stent.

This pilot project provided:

• unprecedented insights into the development of forces and stresses during a systolic pulse,
• a demonstration of the stability and robustness of the stent under the simulated conditions,
• in-depth information not accessible with experimental measurements,
• a tailored modeling procedure for the prediction of stent stability and lifetime under different working conditions.

A realistic simulation process was set up using the ANSYS Multiphysics platform. Starting with an expanded stent (Fig. Position a), an initial structural analysis provided the stress and deformation state after crimping and positioning against the aortic wall (Fig. Position b). The prestressed structure was then connected to the leaflet valves of the heart (Fig. position c). During a transient fluid-structure interaction analysis, the stent and aortic wall were then considered and the compressive forces were transferred from the blood to the leaflet valves (Fig. position d). The evolution of stresses in the stent material nitinol were determined over a complete systolic pulse beat (Fig. Stent model with diagram). The anisotropic material properties of the pericardium were considered as well as a material model for the shape memory alloy Nitinol and a non-Newtonian viscosity model for human blood.