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Transcatheter aortic valve replacement (TAVR) is an established treatment for high-risk patients with severe symptomatic aortic stenosis. It is well-known that leaflet shape has a key role in hemodynamic performance and durability of bioprosthetic valves. Excessive mechanical stress on transcatheter aortic valve (TAV) leaflets may lead to accelerated tissue degeneration and diminished long-term valve durability. Recently, model-based design of medical devices using computational modeling and simulations is being increasingly used in addition to traditional method using time consuming bench-top and pre-clinical animal testing. The aim of this study was to develop an automated optimization framework to reduce TAV leaflet stress under physiological loading condition to improve tissue durability and increase valve durability.
MATLAB, SolidWorks and ABAQUS/Explicit were linked together using Isight software. Leaflet curves were sketched using second-order non-uniform rational B-splines (NURBS) generated in a home-developed MATLAB code. A transvalvular pressure gradient waveform obtained from in-vitro tests was applied to the leaflet as dynamic loading in the simulations. The leaflet was assumed to be isotropic, incompressible, and nonlinear hyperelastic material. Parametric inputs were optimized using particle swarm optimization method in Isight to minimize the maximum principal stress.
An optimized leaflet geometry was obtained and leaflet stress values were compared to Edwards SAPIEN XT. High stress regions were observed primarily in the fixed boundary edge at the peak of systole and commissures at the peak of diastole. The simulation results showed that the peak of stress in the optimized geometry reached to 1.18 MPa. Whereas, the maximum principal stress value was 1.32 MPa for SAPIEN XT.
A computational simulation was developed to optimize the TAV leaflet shape under a dynamic loading condition. Our results indicated the peak of stress in the optimized geometry was 12% less than Edwards SAPIEN XT design. The developed optimization framework may provide a TAV design with longer valve durability in comparison to the currently available TAVs used in clinical practice.
STRUCTURAL: Valvular Disease: Aortic