Biomechanical impact of material parameters and cross-sectional size of a commercial transcatheter aortic valve: a finite element study

Transcatheter aortic valve (TAV) implantation is an established minimally invasive alternative to surgical valve replacement for the treatment of aortic stenosis. Further studies are currently being conducted to increase TAV treatment effectiveness and safety. Within this context, finite element analysis represents an eligible tool to address these challenges. Computational modeling can be adopted to both support the device design phase, reducing times and costs associated with the development cycle, and predict the TAV implantation outcomes, improving the treatment results. In this study, the recently developed Portico TAV (Abbott, USA) was modeled and compared to the commercially available CoreValve TAV (Medtronic, Ireland), by simulating the deployment of the devices in three different idealized aortic root anatomy models through finite element (FE) analyses. The creation of the Portico TAV model was based on the frame structure geometrical data collected from literature, two-dimensional images, and manufacturer information. The geometrical model was then meshed using 1D beam elements. The aortic root models used for the FE analyses represented one healthy and two diseased leaflets’ conditions, resembling natural anatomical features. Different material properties were assigned to each component, basing the choice on previously conducted studies. Post-processing and comparisons were conducted using biomechanical quantities (e.g. pullout force magnitude, peak maximum principal stress in the aortic wall, peak contact pressure in the left ventricular outflow tract (LVOT)) to evaluate the mechanical performance of the implanted device. The Portico TAV presented lower performances compared to the CoreValve TAV, in terms of anchoring and paravalvular leakage risk. Thereafter, in this circumstance, an optimization of the frame was performed by carrying out a sensitivity analysis of the Nitinol material parameters and elements cross-sectional size. Three material parameters (i.e. austenite elasticity (EA), end of transformation unloading (σUE), and the difference (σUS - σUE)) were identified as the most influencing the TAV deployment from a biomechanical viewpoint. Then, an optimization procedure was applied to study their effect on a multi-variable level. In conclusion, cross-sectional frame sizes and specific material parameters tuning were observed to have a strong influence on the improvement of biomechanical outcomes of Portico TAV simulations and were thus used for this purpose.