PoliTo(BIO)Med Lab, Department of Mechanical and Aerospace Engineering, Politecnico di Torino, Turin, Italy.
Laboratory of Biological Structure Mechanics (LaBS), Department of Chemistry, Materials and Chemical Engineering "Giulio Natta", Politecnico di Milano, Milan, Italy.
J Mech Behav Biomed Mater. 2023 Feb;138:105623. doi: 10.1016/j.jmbbm.2022.105623. Epub 2022 Dec 12.
Self-expandable transcatheter aortic valves (TAVs) elastically resume their initial shape when implanted without the need for balloon inflation by virtue of the nickel-titanium (NiTi) frame super-elastic properties. Experimental findings suggest that NiTi mechanical properties can vary markedly because of a strong dependence on the chemical composition and processing operations. In this context, this study presents a computational framework to investigate the impact of the NiTi super-elastic material properties on the TAV mechanical performance. Finite element (FE) analyses of TAV implantation were performed considering two different TAV frames and three idealized aortic root anatomies, evaluating the device mechanical response in terms of pullout force magnitude exerted by the TAV frame and peak maximum principal stress within the aortic root. The widely adopted NiTi constitute model by Auricchio and Taylor (1997) was used. A multi-parametric sensitivity analysis and a multi-objective optimization of the TAV mechanical performance were conducted in relation to the parameters of the NiTi constitutive model. The results highlighted that: five NiTi material model parameters (E, σ, σ, σ and σ) are significantly correlated with the FE outputs; the TAV frame geometry and aortic root anatomy have a marginal effect on the level of influence of each NiTi material parameter; NiTi alloy candidates with pareto-optimal characteristics in terms of TAV mechanical performance can be successfully identified. In conclusion, the proposed computational framework supports the TAV design phase, providing information on the relationship between the super-elastic behavior of the supplied NiTi alloys and the device mechanical response.
自扩张经导管主动脉瓣（TAV）在植入时无需球囊充气即可弹性恢复其初始形状，这得益于镍钛（NiTi）框架的超弹性特性。实验结果表明，由于 NiTi 机械性能强烈依赖于化学成分和加工操作，因此其机械性能可能会有很大差异。在这种情况下，本研究提出了一种计算框架，以研究 NiTi 超弹性材料性能对 TAV 机械性能的影响。考虑到两种不同的 TAV 框架和三种理想化的主动脉根部解剖结构，进行了 TAV 植入的有限元（FE）分析，评估了 TAV 框架施加的拔出力大小和主动脉根部内的峰值最大主应力等设备机械响应。采用了 Auricchio 和 Taylor（1997）提出的广泛采用的 NiTi 构成模型。针对 NiTi 本构模型的参数进行了 TAV 机械性能的多参数灵敏度分析和多目标优化。结果表明：NiTi 材料模型的五个参数（E、σ、σ、σ和σ）与 FE 输出显著相关；TAV 框架几何形状和主动脉根部解剖结构对每个 NiTi 材料参数的影响水平有一定影响；可以成功识别在 TAV 机械性能方面具有帕累托最优特性的 NiTi 合金候选材料。总之，所提出的计算框架支持 TAV 的设计阶段，提供了有关所提供的 NiTi 合金的超弹性行为与器件机械响应之间关系的信息。
