The Effect of Angle and Flow Rate Upon Hemodynamics in Distal Vascular Graft Anastomoses: A Numerical Model Study

Abstract

Flow in distal end-to-side anastomoses of iliofemoral artery bypass grafts was simulated using a steady flow, three-dimensional numerical model. With the proximal artery occluded, anastomotic angles were varied over 20, 30, 40, 45, 50, 60 and 70 deg while the inlet Reynolds numbers were 100 and 205. Fully developed flow in the graft became somewhat skewed toward the inner wall with increasing angle for both Reynolds numbers. Separated flow regions were seen along the inner arterial wall (toe region) for angles > or = 60 deg at Re = 100 and for angles > or = 45 deg at Re = 205 while a stagnation point existed along the outer arterial wall (floor region) for all cases which moved downstream relative to the toe of the anastomosis with decreasing angles. Normalized shear rates (NSR) along the arterial wall varied widely throughout the anastomotic region with negative values seen in the separation zones and upstream of the stagnation points which increased in magnitude with angle. The NSR increased with distance downstream of the stagnation point and with magnitudes which increased with the angle. Compared with observations from chronic in vivo studies, these results appear to support the hypothesis of greater intimal hyperplasia occurring in regions of low fluid shear.

Numerical simulation of the haemodynamics in end‐to‐side anastomoses

“…These similarities of the velocity profiles at the maximum flow rate are apparent in all the figures of the velocity fields presented above. These findings are in line with the results of steady-flow finite element model simulations and in vitro studies of various authors [2,25,26].…”

Access Blood Flow and the Risk of Complications in Mature Forearm and Upper Arm Arteriovenous Fistulas

“…The absence of a relation between baseline Qa and the time to AVF complication suggests involvement of additional aspects such as vessel wall characteristics or surgical techniques. For instance, increased anastomosis angles cause increased flow separation regions near the toe of the anastomosis [29][30][31] , and more extreme variations in time-averaged wall shear stress and oscillatory shear along the bed of the anastomosis [32] . To what extent these aspects are involved remains speculative and requires further investigation.…”

Numerical Simulation of Turbulent Blood Flow in the System of Coronary Arteries with Stenosis

“…Figure 8 presents the velocity field of blood flow in the system of coronary arteries with the 75% stenosed LCA at the peak of systole [30][31][32][33]. The result indicates that blood travels through the LCA with mean velocity of about 0.23 m/s, and its velocity increases along the vessel where the highest velocity of about 3 m/s appears at the constricted cross-section of the stenosis area as shown in Figure 8.…”