The influence of competitive flow on graft patency

To evaluate the effects of competitive flow, bilateral aorto-iliac ePTFE grafts, 10 cm in length and with an internal diameter of 6 mm, were placed in ten mongrel dogs. On one side the external iliac artery was ligated (the control side); on the opposite side (the experimental side) flow continued through the native aorto-iliac system, as well as the graft, to allow a situation of competitive flow. Flow measurements showed the experimental graft carried 38.6% of the total blood flow going to the ipsilateral external iliac artery. After 30 days the grafts were exposed and patency and flow were evaluated by Doppler ultrasound. The control side showed 60% patency; all of the grafts on the experimental side were occluded. In addition, complete endothelial healing was observed at the occluded ostia of all experimental grafts. We conclude that competitive flow does influence graft patency and that graft thrombosis appears to be a relatively early phenomenon, as evidenced by the endothelial healing which occurred.