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

Abstract

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>1.4Pa^(-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.