Doppler color flow images of iliofemoral graft end-to-side distal anastomotic models

Abstract

Hemodynamics within the distal anastomoses of iliofemoral bypass grafts were simulated using Plexiglas models (2.5 cm ID) within a pulsatile flow loop system (Re(mean) = 92, Re(peak) = 459 and alpha = 3.56). End-to-side distal anastomoses were constructed with angles of 30 degrees, 45 degrees and 60 degrees to bypass proximal artery segments with stenoses of 60% and 100% diameter reduction. Velocities were obtained over a two-dimensional field within the artery using an ultrasonic Doppler color flow imager operating at 5 MHz at positions from 1.5 diameters upstream to 3 diameters downstream of the anastomosis. Flow patterns downstream of an occlusion demonstrated definite skewing effects toward the outer wall with resultant flow separation along the inner wall. Presence of a partial (60% diameter reduction) arterial stenosis upstream of the anastomosis produced flow separation along both artery walls and a more symmetric profile downstream. Measurement of a separation area index (SAI) along each arterial wall demonstrated a minimum area exposed to low velocities for the 30 degrees anastomotic angle compared to the 45 degrees and 60 degrees anastomotic angles and for the occluded proximal artery cases compared to corresponding stenotic artery cases. The SAI values were minimal at peak systole compared to successive quarter cycle intervals. The findings of this study provide further information regarding the relationship between local fluid mechanics and predominant sites for intimal hyperplasia formation.