Impact of juxta-anastomotic stent implantation on the haemodynamics within a single representative patient AVF

Abstract

An arteriovenous fistula (AVF), a vascular structure surgically created to enable haemodialysis, is commonly affected by stenosis in the juxta-anastomotic region. A new treatment involving the implantation of a flexible stent has shown good potential for retaining healthy AVFs. Since vascular disease in the AVF is known to be related to the haemodynamic environment within the vasculature, this study aims to understand the impact of the stent implantation on the flow dynamics within a single patient-specific AVF. A virtual stented geometry of the AVF was obtained with micro-CT images of a benchtop AVF model implanted with a Supera stent. Reynolds averaged Navier–Stokes simulations were conducted with physiological boundary conditions (Reynolds numbers varying from 345 to 730) applied on the AVF model with and without the presence of the stent. Velocity contour slices within the vein showed the concentration of high velocity in the stent encapsulated region. Moreover, the ratios of flow rate across the stent-lumen cross-sections over the flow rate across the vessel-lumen cross-sections suggested that the flow was being funnelled through the stent encapsulated regions of a malapposed section, despite the porous structure of the stent. A larger low velocity recirculation region translated to a larger vessel wall area of high Oscillatory Shear Index (OSI) and low Time-Averaged Wall Shear Stress (TAWSS) in the AVF model with the stent absent, compared to the stented model. This suggested that the adverse haemodynamic behaviour was being funnelled away from the vessel wall, possibly leading to a protective environment in the malapposed region of the vein.