Development and validation of a numerical model for the investigation of transcatheter aortic valve implantations
Final Report Abstract
Aortic valve diseases, especially aortic stenosis, is an increasing issue in the elderly population. One treatment option is the minimally invasive implantation of a transcatheter heart valve prosthesis by means of a catheter. The goal of the project was to develop a fully coupled fluid structure interaction model to analyse the flow field behind the heart valve prosthesis. In the scope of the project an innovative computational model was developed that can be applied to any prosthesis design to study the resulting flow field. The main novelty of the project is the development of a fully coupled ICFD FSI model for the transcatheter aortic CoreValve prosthesis. This goes beyond the state of the art, which uses mostly the ALE FSI method for modelling of the aortic flow. Unfortunately, this ALE method has limitations. First, the fluid mesh size plays an important role in the size of the velocity gradient. This method does not account for the boundary layer effect and as result, the velocity gradient is strongly dependent on the mesh size, e.g. a larger mesh size results in a larger gradient area and a smaller mesh size in a smaller area. Second, the stent of the prosthesis was excluded in the FSI simulations due to much higher computational costs. Third, the ALE approach need to be modelled with hexahedral elements. Unfortunately, the patient’s anatomy models are modelled with triangular elements, which are incompatible to this approach. The fully coupled ICFD FSI approach looks very promising in modelling the flow in detail, because smaller mesh sizes can be used. This leads to a high resolution velocity field, where small backflow areas and vortices can be seen. Unfortunately, as the volume fluid mesh is built from the surface meshes, the cost of building high quality meshes is high. As this method is relatively new, some issues with the solver versions occurred and a developer version was used, which fixed some problems. Some limitations remained as only a zero pressure boundary condition could be applied at the outlet. Further, only the RANS turbulence model worked with this solver. The stent was also excluded from the simulation due to enormous computational costs. The boundary layer mesh at the aortic wall could not be used as in the small gap between skirt and aortic wall would occur high leakage flow. Future work will include patient-specific simulations including the geometries in WP3 and considering calcification patterns, neo-sinus washout and the effect of implant height on paravalvular leakage and coronary flow.
Publications
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Fluid-Structure Interaction Model of a Percutaneous Aortic Valve: Comparison with an In Vitro Test and Feasibility Study in a Patient-Specific Case. Ann Biomed Eng. 2016 Feb; 44(2):590-603
Wu W, Pott D, Mazza B, Sironi T, Dordoni E, Chiastra C, Petrini L, Pennati G, Dubini G, Steinseifer U, Sonntag S, Kuetting M, Migliavacca F
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Fluid–Structure Simulation of a Transcatheter Aortic Valve Implantation: Potential Application to Patient-Specific Cases. In book: Computer Methods in Biomechanics and Biomedical Engineering, 2017; pp. 93-98
Wu W, Pott D, Chiastra C, Petrini L, Pennati G, Dubini G, Steinseifer U, Sonntag S, Kuetting M, Migliavacca F
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Fluid-structure interaction of a pulsatile flow with an aortic valve model: A combined experimental and numerical study. Int J Numer Meth Biomed Engng. 2018; 34:e2945
Sigüenza J, Pott D, Mendez S, et al.
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Hemodynamics inside the neo- and native sinus after TAVR: Effects of implant depth and cardiac output on flow field and coronary flow. Artif Organs. 2021;45:68–78
Pott D, Sedaghat A, Schmitz C, et al.
