Development and validation of a numerical model for the investigation of transcatheter aortic valve implantations

经导管主动脉瓣植入术对于严重主动脉狭窄的高危患者来说是一种微创的选择。由于缺乏长期经验以及干预期间和之后存在的并发症，这种相当新的方法不能替代传统的外科手术。瓣旁主动脉瓣瓣反流是最常见的并发症。然而，目前的研究仅基于临床结果的经验数据。该项目的目的是开发和实验体外验证一种新的模拟模型，使潜在并发症的系统研究成为可能。其中一个主要任务是血流和心脏瓣膜叶的流体结构相互作用的建模。对网格、材料特性、边界条件、耦合和湍流进行广泛的数值分析对于求解过程的准确性和稳定性是必不可少的。为此目的，进行体外试验以验证数值模型并根据需要进行调整。通过验证的仿真模型，可以随后评估假体错位的影响。患者特定的心脏和周围血管的几何形状是根据严重主动脉狭窄患者的医学成像数据创建的。假体实际上被植入不同的位置。植入部位对瓣旁漏的敏感性是与临床伙伴密切合作评估的。本研究项目的长期目标是开发一种方法，使负责干预的医生对可能的策略（例如选择植入位置和假体大小）的决策客观化，以优化治疗结果。

Transcatheter aortic valve implantation is a minimal-invasive alternative for high-risk patients with severe aortic stenosis when open-heart surgery carries to much risk. Because of missing long-term experience and existing complications during and after the intervention, this rather new approach is not a replacement of the classic surgical procedure. Paravalvular aortic regurgitation due to malposition of the prosthesis is the most frequent complication. Current studies, however, are only based on empirical data of clinical outcomes.The aim of this project is the development and experimental in-vitro validation of a novel simulation model which makes the systematic study of potential complications possible. One of the main tasks is the modeling of the fluid-structure-interactions of the blood flow and the heart valve leaflets. An extensive numerical analysis of the mesh, the material properties, the boundary conditions, the coupling and the turbulence are indispensable with respect to accuracy and stability of the solution process. For this purpose, in vitro tests are performed to validate the numerical model and make adjustments as needed. By using the validated simulation model, the effects of malpositioning of the prosthesis can subsequently be evaluated. Patient specific geometries of the heart and surrounding vessels are created based on medical imaging data from patients suffering from severe aortic stenosis. The prosthesis is virtually implanted at different locations. The sensitivity of the implantation site on paravalvular leakage is evaluated in close cooperation with a clinical partner. The long-term aim of this research project is the development of a methodology that objectifies the decision making of the doctors in charge about possible strategies of the intervention (e.g. choice of implantation site and prosthesis size) in order to optimize the outcome of the treatment.