Tailoring of arteriovenous graft-to-vein anastomosis angle to attenuate pathological flow fields

Abstract

Arteriovenous grafts are routinely placed to facilitate hemodialysis in patients with end stage renal disease. These grafts are conduits between higher pressure arteries and lower pressure veins. The connection on the vein end of the graft, known as the graft-to-vein anastomosis, fails frequently and chronically due to high rates of stenosis and thrombosis. These failures are widely believed to be associated with pathologically high and low flow shear strain rates at the graft-to-vein anastomosis. We hypothesized that consistent with pipe flow dynamics and prior work exploring vein-to-artery anastomosis angles in arteriovenous fistulas, altering the graft-to-vein anastomosis angle can reduce the incidence of pathological shear rate fields. We tested this via computational fluid dynamic simulations of idealized arteriovenous grafts, using the Bird-Carreau constitutive law for blood. We observed that low graft-to-vein anastomosis angles ($$<20^{\circ }$$ < 20 ∘ ) led to increased incidence of pathologically low shear rates, and that high graft-to-vein anastomosis angles ($$>40^{\circ }$$ > 40 ∘ ) led to increased incidence of pathologically high shear rates. Optimizations predicted that an intermediate ($$\sim 30^\circ$$ ∼ 30 ∘ ) graft-to-anastomosis angle was optimal. Our study demonstrates that graft-to-vein anastomosis angles can significantly impact pathological flow fields, and can be optimized to substantially improve arteriovenous graft patency rates.

Sutureless vascular anastomotic approaches and their potential impacts

“…Another factor predisposing to thrombosis is changes in blood flow along the endothelium. Understanding blood flow dynamics is crucial in the development of intraluminal sutureless anastomotic devices [ 142 , 143 ]. Wall shear stress (WSS), the frictional force exerted by blood flow on the endothelial surface, is a key parameter in these dynamics.…”

A critical review of surgical strategies to minimise venous stenosis in arteriovenous grafts

“…CFD analysis supports this with a clear haemodynamic impact of flow and angle. 33 A further 10 years of additional computing power has allowed this to be substantially refined with a recent report showing not only abnormal shear rates either high or low shear rates with angles >40°and <15° 34 . Despite the significantly complex mathematical modelling performed, many assumptions are required such as vessel size, viscosity, blood pressure, AVG configuration and anastomosis shape any of which could alter the findings.…”

Evaluation of the Effects of Anastomosis Angle on the Performance of an Optimized Spiral Flow-Inducing Graft Design using CFD

“…Different graft designs have been evaluated using CFD. Some graft design parameters that have been looked into using CFD include the anastomosis angle [14][15][16], graft diameter [16,17], and the use of cuffs [18,19], among others. In a study by Ruiz-Soler et al, [20] they used CFD to assess the use of ridges in graft design to improve hemodynamics within the graft.…”

“…The attachment angle between the graft and the native blood vessel heavily impacts the flow field, particularly in the vicinity of the attachment site. As such, the optimization of the anastomosis angle can potentially improve the performance and prolong the patency of grafts [21].…”