Blood flow in distal end-to-side anastomoses with PTFE and a venous patch:Results of an in vitro flow visualisation study

Objectives: non-physiological flow behaviour plays a significant role in th e development of distal anastomotic intimal hyperplasia. To investigate flo w patterns in four anastomotic types of femoral end-to-side distal bypass g raft anastomoses, a flow visualisation study was performed. Methods: transparent 1:1 casted replicas of distal vascular graft anastomos es created by conventional technique, Miller-cuff, Taylor- and Linton-patch were fabricated. A pulsatile mock circulation with a high-speed video syst em was constructed. Flow pattern was determined at mean Reynolds numbers 10 0-500. Migrations of the stagnation points on the bottom of the anastomoses at mean Reynolds numbers 100, 230, and 350 were measured. Results: a vortex forms during early systole and increases to maximum systo le in all anastomoses. During the diastolic phase the vortex moves in the M iller-cuff distally to the toe of the anastomosis and remains standing, whi le in the other anastomotic types the vortex moves proximally to the heal o f the junction and breaks down. The shift of the stagnation point in the Mi ller-cuff was considerably smaller than in the other anastomoses. Conclusion: conventional, Linton and Taylor anastomoses show similar flow p atterns. The Miller-cuff with its wider cavity shows lower shift of the bot tom stagnation point, but a persistent washout of the anastomotic cavity, w hich may contribute to its reported good clinical performance.