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

当心内直视手术风险很大时，经导管主动脉瓣置入术是一种微创的替代方法，适用于患有严重主动脉狭窄的高危患者。由于缺乏长期的经验和在介入过程中和之后存在的并发症，这种相当新的方法并不能取代经典的外科手术程序。假体错位引起的瓣膜旁主动脉瓣返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一种新的模拟模型并进行体外实验验证，使系统研究潜在的并发症成为可能。主要任务之一是对血液流动和心脏瓣叶的流体-结构-相互作用进行建模。对于求解过程的精度和稳定性而言，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是不可或缺的。为此，进行了体外试验，以验证数值模型并根据需要进行调整。通过使用经过验证的模拟模型，可以随后评估假体位置错误的影响。患者特定的心脏和周围血管的几何形状是基于来自严重主动脉狭窄患者的医学成像数据创建的。假体实际上被植入到不同的位置。与临床伙伴密切合作，评估植入部位对瓣膜旁渗漏的敏感性。这项研究项目的长期目标是开发一种方法，使主管医生对可能的干预策略(如植入位置和假体大小的选择)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.