Development of a methodology for in vitro and in silico simulation of transcatheter aortic valve replacement using 3D-printed valve frames

Background: Transcatheter aortic valve implantation (TAVI) is experiencing continued growth as an option for the treatment of aortic stenosis. Both in vitro and in silico methods have proven reliable in assessing the performance of TAVI devices, which can be used in procedure planning and prototyping new concepts. 3D printing of TAVI frames has the potential for revolutionizing frame designs by making it possible to create more complex geometries. However, the mechanical performance of additively manufactured frames, in terms of crimping and deployment into an aortic root, needs to be verified if such frames are to provide a plausible and reliable method for benchtop testing. Methods: Having previously established a suitable set of process parameters for laser powder bed fusion (LPBF) manufacture of TAVI frames based on the SAPIEN S3 design, the deployment of such a frame into a patient-specific, 3D printed aortic root phantom was undertaken and assessed using a high resolution CT scan of the result. In parallel, a full computational model was developed to simulate the same deployment procedure and validated against the in vitro study. Further, an interesting case study was setup using this approach to assess deployment of the LPBF frame into the same aortic root phantom but with two of the leaflets fused together. Results: The LPBF-manufactured frame had sufficient radial strength to fully open the leaflets within the aortic root phantom and anchor the frame in place for both fused and non-fused leaflet cases. There was good agreement between the in vitro and in silico tests in terms of frame position with an average nodal position error of 0.37 mm and 1.29 mm for non-fused and fused cases respectively. Similarly, the frame diameter difference between the in vitro and in silico deployments were 1.01% for the non-fused and 3.17% for the fused cases. Conclusion: Manufacture of a SAPIEN S3 type heart valve frame using LPBF has been shown to provide a viable procedure for producing frames for testing and assessment when crimped and deployed into a model of an aortic root. Further, the validated in silico model developed in this study can be used to computationally design and test novel frame concepts to be manufactured by LPBF.