An in silico study of the influence of vessel wall deformation on neointimal hyperplasia progression in peripheral bypass grafts

Abstract

Neointimal hyperplasia (NIH) is a major obstacle to graft patency in the peripheral arteries. A complex interaction of biomechanical factors contribute to NIH development and progression, and although haemodynamic markers such as wall shear stress have been linked to the disease, these have so far been insufficient to fully capture its behaviour. Using a computational model linking computational fluid dynamics (CFD) simulations of blood flow with a biochemical model representing NIH growth mechanisms, we analyse the effect of compliance mismatch, due to the presence of surgical stitches and/or to the change in distensibility between artery and vein graft, on the haemodynamics in the lumen and, subsequently, on NIH progression. The model enabled to simulate NIH at proximal and distal anastomoses of three patient-specific end-to-side saphenous vein grafts under two compliance-mismatch configurations, and a rigid wall case for comparison, obtaining values of stenosis similar to those observed in the computed tomography (CT) scans. The maximum difference in time-averaged wall shear stress between the rigid and compliant models was 3.4 Pa, and differences in estimation of NIH progression were only observed in one patient. The impact of compliance on the haemodynamic-driven development of NIH was small in the patient-specific cases considered.

Hemodynamics and Wall Mechanics of Vascular Graft Failure

“…184,185 Computational simulations in models with deformable walls suggest that neointimal growth is linked to regions with both low WSS and a high OSI, where such regions do not localize to any particular graft position and exhibit significant heterogeneity in the degree of stenosis. 186,187 However, simulations with larger patient cohorts using these methods are necessary to establish clear thresholds, as the degree of patient-to-patient variability limits the extrapolation of these results to inform clinical decisions.…”

Experience of Patient-Specific CFD Simulation of Blood Flow in Proximal Anastomosis for Femoral-Popliteal Bypass

“…The ANSYS CFX fluid dynamics package was used for the calculations, solving the non-stationary three-dimensional Navier-Stokes Equation (3) using the finite volume method. This software, well validated for 3D flow computations based on the Navier-Stokes equations, was widely used for previous related patient-specific simulations [22,23,[26][27][28]. A second-order accuracy scheme was used to evaluate convective and diffusion fluxes at the control volume faces.…”

“…Patient-specific CFD simulations are based on the use of personalized data, including geometry, inlet and outlet flow rates and others. Geometric models of arteries and grafts are usually obtained from magnetic resonance imaging data [15,24,25] or computed tomography (CT) data [18,22,[26][27][28]. Both of these methods are used in patient-specific simulation, but computed tomography is more common due to its simplicity.…”

“…In several papers [26][27][28], patient-specific numerical simulations of the blood flow in femoral-popliteal bypass by vein graft were performed. The authors of these contributions considered numerical results together with CT measurements to compare wall shear stress areas with neointima growth areas.…”

V Flow Measurements of Pulsatile Flow in Femoral-Popliteal Bypass Proximal Anastomosis Compared with CFD Simulation

“…Significant disturbances in the physiological structure of blood flow are also observed in the areas of vessels' connection with synthetic prostheses of the "end-to-side" type, namely, in the areas of proximal and distal anastomoses. It can lead to neointimal hyperplasia, thrombosis of prostheses, and their complete blockage, requiring reoperation [8,9].…”