Patient-specific compliant simulation framework informed by 4DMRI-extracted Pulse Wave Velocity: Application post-TEVAR

We introduce a new computational framework that makes use of the Pulse Wave Velocity (PWV) extracted exclusively from 4D flow MRI (4DMRI) to inform patient-specific compliant computational fluid dynamics (CFD) simulations of a Type-B aortic dissection (TBAD), post-thoracic endovascular aortic repair (TEVAR). From 4DMRI and brachial pressure, a 3D inlet velocity profile (IVP), dynamic outlet boundary, and reconstructed thoracic aortic geometry are obtained. A moving boundary method (MBM) is applied to simulate aortic wall displacement. The aortic wall stiffness was estimated through two methods: one relying on area-based distensibility and the other utilising regional pulse wave velocity (RPWV) distensibility, further fine-tuned to align with in vivo values. Predicted pressures and outlet flow rates were within 2.3% of target values. RPWV-based simulations were more accurate in replicating in vivo hemodynamic compared to the area-based ones. RPWVs were closely predicted in most regions, with the exception being the endograft, and systolic flow reversal ratios (SFRR) were accurately captured, while a difference of above 60% on in-plane rotational flow (IRF) between the simulations. Significant disparities between the wall shear stress (WSS)-based indices were observed between the two approaches, especially the endothelial cell activation potential (ECAP). At the isthmus, the RPWV-driven simulation indicated a mean ECAP>1.4 Pa ^(-1) (critical threshold), indicating areas potentially prone to thrombosis. In contrast, the area-based simulation did not depict this. RPWV-driven simulation results agree well with 4DMRI measurements, emphasising that RPWV simulations are accurate in simulating haemodynamics, consequently facilitating a comprehensive assessment of surgery decision-making and potential complications, such as thrombosis and aortic growth. ### Competing Interest Statement The authors have declared no competing interest. ### Funding Statement We thank the Department of Mechanical Engineering at University College London, the Wellcome EPSRC Centre for Interventional Surgical Sciences (WEISS) (203145Z/16/Z), the British Heart Foundation (NH/20/1/34705), the Biotechnology and Biological Sciences Research Council (BBSRC) and UK Research and Innovation (UKRI) (BB/X005062/1) for their funding support. ### Author Declarations I confirm all relevant ethical guidelines have been followed, and any necessary IRB and/or ethics committee approvals have been obtained. Yes The details of the IRB/oversight body that provided approval or exemption for the research described are given below: Inselspital Bern - ethically approved protocol: Local Institutional Review Board ID 2019-00556. I confirm that all necessary patient/participant consent has been obtained and the appropriate institutional forms have been archived, and that any patient/participant/sample identifiers included were not known to anyone (e.g., hospital staff, patients or participants themselves) outside the research group so cannot be used to identify individuals. Yes I understand that all clinical trials and any other prospective interventional studies must be registered with an ICMJE-approved registry, such as ClinicalTrials.gov. I confirm that any such study reported in the manuscript has been registered and the trial registration ID is provided (note: if posting a prospective study registered retrospectively, please provide a statement in the trial ID field explaining why the study was not registered in advance). Yes I have followed all appropriate research reporting guidelines, such as any relevant EQUATOR Network research reporting checklist(s) and other pertinent material, if applicable. Yes All data produced in the present study are available upon reasonable request to the authors