Biomechanical Simulations of Transcatheter Aortic Valve

Since the first-in-human transcatheter aortic valve (TAV) implantation in 2002, there has been rapid growth in its use throughout the world for treatment of severe symptomatic aortic stenosis in patients who are at high surgical risk. TAV implantation has been confirmed by clinical studies as an alternative to the traditional surgical aortic valve replacement in inoperable and high-risk aortic stenosis patients. Computational and experimental assessment of TAVs is essential to evaluate the efficacy and pitfalls of this new procedure. However, comprehensive study on TAV implantation from an engineering perspective is lacking. Thus, in this work, it is proposed to develop computational models to investigate the effects of leaflet compliance, valve geometry and fluid-structure interaction (FSI) on the functioning and biomechanics of TAV devices in both circular and elliptical configurations. Mechanical properties of TAV leaflets were obtained from planar biaxial testing of glutaraldehyde treated thin bovine and porcine pericardial tissues, and characterized by Fung-type nonlinear anisotropic hyperelastic material model. Simulations were performed to examine the effects of tissue thickness and anisotropy on the valve deformation and stress distribution. Due to the distortion of TAVs after implantation, elliptical TAV models were also developed to investigate the effect of valve distortion on the stress and strain responses. In addition, since the impact of 2D leaflet geometry on the valve stress distribution is unclear, we proposed a probabilistic computational strategy to investigate the effect of the leaflet geometry on the valve stress response. Finally, to validate the quasi-static finite element modeling approach and to evaluate the valve effective orifice area, FSI analyses of TAV opening and closing using the smoothed particle hydrodynamics method was performed. The computational modeling approaches proposed in this work could improve our understanding of the biomechanics involved in the TAV implantations with a circular or elliptical configuration and provide insights on the optimal design of next-generation TAV devices