Numerical modeling of transcatheter aortic valve implantation using a fluid-structure interaction approach

Background: Nowafays, transcatheter aortic valve implantation is an effective method for treating patients with severe aortic stenosis in all surgical risk groups. Despite significant achievements, the transcatheter aortic valve implantation proceeding is often accompanied by a number of obstacles associated with suboptimal location of the bioprosthesis, its geometry and subsequent hydrodynamic disturbances. Objective: The aim of the study was to develop and validate a comprehensive mathematical model taking into account fluid-structure interaction to simulate the hemodynamic characteristics of transcatheter aortic valves. Methods: To construct a comprehensive model describing the hemodynamics of the aortic valve, the first step was to develop a geometric model including the aortic root, the valve frame, and the leaflet apparatus connected to the valve skirt. Next, the overall topic on modeling the flow and soft tissue response during valve placement was solved using the ALE formulation for fluid-structure interaction, which combines the Eulerian description of fluid motion with the Lagrangian description of solid deformation. Results: Stress distributions in the valve frame and cusps were obtained. The highest stress occurred at the frame nodes and reach 270 MPa. The valve cusps were most susceptible to high stress in the inflection zone. Stress values ranged from 5–10 MPa. Furthermore, aortic wall dilation due to valve frame expansion was determined to be in the range of 0.6–1.2 mm and consistent with clinically observed values. The maximum flow velocity after surgery did not exceed 1.4 m/s that was within a range for healthy people. Conclusion: The study demonstrates the possibility of using a comprehensive approach based on the fluid-structure interaction to simulate the hemodynamics of a transcatheter aortic valve bioprosthesis. The developed model covers both the anatomically correct geometry of the aortic root and valve elements, and realistic boundary conditions based on clinical echocardiography data and a physiological pressure profile that ensures high reliability of the numerical experiment. Thus, the presented methodological approach can be effectively used to assess and predict the results of transcatheter aortic valve implantation and optimize new designs of transcatheter aortic bioprostheses, analyze their interaction with the anatomical structures of the patient, as well as to reduce the risk of complications and increase the durability of prostheses.