THE EFFECT OF ANGLE AND FLOW-RATE UPON HEMODYNAMICS IN DISTAL VASCULAR GRAFT ANASTOMOSES - A NUMERICAL-MODEL STUDY

Flow in distal end-to-side anastomoses of iliofemoral artery bypass gr afts was simulated using a steady flow, three-dimensional numerical mo del. With the proximal artery occluded, anastomotic angles were varied over 20, 30, 40, 45, 50, 60 and 70 deg while the inlet Reynolds numbe rs were 100 and 205. Fully developed flow in the graft became somewhat skewed to ward the inner wall with increasing angle for both Reynolds numbers. Separated flow regions were seen along the inner arterial wa ll (toe region) for angles greater than or equal to 60 deg at Re = 100 and for angles greater than or equal to 45 deg at Re = 205 while a st agnation point existed along the outer arterial wall (floor region)for all cases which moved downstream relative to the toe of the anastomos is with decreasing angles. Normalized shear rates (NSR) along the arte rial wall varied widely throughout the anastomotic region with negativ e values seen in the separation zones and upstream of the stagnation p oints 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 v ivo studies, these results appear to support the hypothesis of greater intimal hyperplasia occurring in regions of low fluid shear.