Abstract
Arterio-Venous Fistulae (AVF) are regarded as the “gold standard” method of vascular access for patients with End-Stage Renal Disease (ESRD) who require haemodialysis. However, up to 60% of AVF do not mature, and hence fail, as a result of Intimal Hyperplasia (IH). Unphysiological flow and oxygen transport patterns, associated with the unnatural and often complex geometries of AVF, are believed to be implicated in the development of IH. Previous studies have investigated the effect of arterial curvature on blood flow in AVF using idealized planar AVF configurations and non-pulsatile inflow conditions. The present study takes an important step forwards by extending this work to more realistic non-planar brachiocephalic AVF configurations with pulsatile inflow conditions. Results show that forming an AVF by connecting a vein onto the outer curvature of an arterial bend does not, necessarily, suppress unsteady flow in the artery. This finding is converse to results from a previous more idealized study. However, results also show that forming an AVF by connecting a vein onto the inner curvature of an arterial bend can suppress exposure to regions of low wall shear stress and hypoxia in the artery. This finding is in agreement with results from a previous more idealized study. Finally, results show that forming an AVF by connecting a vein onto the inner curvature of an arterial bend can significantly reduce exposure to high WSS in the vein. The results are important, as they demonstrate that in realistic scenarios arterial curvature can be leveraged to reduce exposure to excessively low/high levels of WSS and regions of hypoxia in AVF. This may in turn reduce rates of IH and hence AVF failure.
Highlights
End-Stage Renal Disease (ESRD) is characterized by an irreversible loss of kidney function, and is treated predominantly with haemodialysis or renal transplantation.[25,27,61] Efficient haemodialysis is dependent upon high-quality vascular access, allowing the rapid removal of blood, which passes through a dialyser removing metabolic waste and water, before being returned to the body
We have extended previous work by Iori et al.,[32] which investigated the effect of planar arterial curvature on flow and oxygen transport patterns in idealized Arterio-Venous Fistula (AVF) with non-pulsatile inflow conditions, to more realistic non-planar brachiocephalic AVF configurations with pulsatile inflow conditions
Results from our more realistic simulations show that forming an AVF by connecting a vein onto the outer curvature of an arterial bend does not, necessarily, suppress unsteady flow in the artery
Summary
End-Stage Renal Disease (ESRD) is characterized by an irreversible loss of kidney function, and is treated predominantly with haemodialysis or renal transplantation.[25,27,61] Efficient haemodialysis is dependent upon high-quality vascular access, allowing the rapid removal of blood (at up to 450 mL minÀ1), which passes through a dialyser removing metabolic waste and water, before being returned to the body. The preferred method of vascular access[60] is via an established Arterio-Venous Fistula (AVF) created surgically by connecting a patient’s own artery and vein, usually in the arm. Material obtained from immature dialysis access reveals a hyperplastic lesion arising from the intima that progressively occludes the lumen of the vessels, resulting in slow flow, and thrombosis and irreversible loss of the AVF.[2,50] IH is found in the venous section of the AVF close to the anastomosis[2,8,56] and more distally,[8,56]
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