Abstract
Transcatheter aortic valve (TAV) implantation has become an established alternative to open-hearth surgical valve replacement. Current research aims to improve the treatment safety and extend the range of eligible patients. In this regard, computational modeling is a valuable tool to address these challenges, supporting the design phase by evaluating and optimizing the mechanical performance of the implanted device. In this study, a computational framework is presented for the shape and cross-sectional size optimization of TAV frames. Finite element analyses of TAV implantation were performed in idealized aortic root models with and without calcifications, implementing a mesh-morphing procedure to parametrize the TAV frame. The pullout force magnitude, peak maximum principal stress within the aortic wall, and contact pressure in the left ventricular outflow tract were defined as objectives of the optimization problem to evaluate the device mechanical performance. Design of experiment coupled with surrogate modeling was used to define an approximate relationship between the objectives and the TAV frame parameters. Surrogate models were interrogated within a fixed design space and multi-objective design optimization was conducted. The investigation of the parameter combinations within the design space allowed the successful identification of optimized TAV frame geometries, suited to either a single or groups of aortic root anatomies. The optimization framework was efficient, resulting in TAV frame designs with improved mechanical performance, ultimately leading to enhanced procedural outcomes and reduced costs associated with the device iterative development cycle.
Highlights
Transcatheter aortic valve (TAV) implantation has become an established clinical procedure that provides a minimally invasive alternative to open heart surgical valve replacement in medium- to high-risk elderly patients with calcific aortic valve disease and severe aortic stenosis (Tabata et al 2019)
The procedure applied for shape and cross-sectional size optimization of a TAV frame consisted of the following main steps (Fig. 1): (1) finite element (FE) modeling of TAV implantation procedure including an idealized aortic root model and a conventional Nitinol TAV frame model parametrized through a mesh-morphing procedure, (2) formulation of the optimization problem through the definition of the optimization objectives and feasible solution space, (3) coupling the design of the experiment method with the surrogate modeling approach to define an approximate relationship between optimization objectives and design parameters, and (4) identification of the optimal geometric attributes of the TAV frame
Considering the healthy configuration (Fig. 5a, left panel), normal contact forces were mostly exerted from the aortic root to the TAV frame in the left ventricular outflow tract (LVOT), generating a total pullout force magnitude equal to 2.3 N
Summary
Transcatheter aortic valve (TAV) implantation has become an established clinical procedure that provides a minimally invasive alternative to open heart surgical valve replacement in medium- to high-risk elderly patients with calcific aortic valve disease and severe aortic stenosis (Tabata et al 2019). Considerable technological advances were conducted to improve the performance and safety of TAVs, several complications still affect the potential of the treatment and are becoming of more concern with the expansion to younger and lower-risk patients (De Biase et al 2018). The most common complications affecting the current generation of TAV devices include postoperative paravalvular leak (PVL), conduction abnormalities, and valve thrombosis (Rotman et al 2018). Aortic root damage and prosthesis migration, which are typically associated with the mutual interaction between the TAV and the aortic root, may occur (Neragi-Miandoab and Michler 2013)
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