The Ratio of Diameters Between the Target Artery and the Bypass Modifies Hemodynamic Parameters Related to Intimal Hyperplasia in the Distal End-to-Side Anastomosis

Abstract

Hemodynamics in the distal end-to-side anastomosis is related to early development of intimal hyperplasia and bypass failure. In this study we investigated the effect of diameter ratios between the target artery and the bypass at three different angles of the connection. The pulsatile flow field was visualized using particle image velocimetry in transparent models with three different angles of the connection (25°, 45°, 60°) and the diameter ratio between the bypass and the target artery was 4.6 mm : 6 mm, 6 mm : 6 mm, and 7.5 mm : 6 mm. Six parameters including location and oscillation of the stagnation point, local energy dissipation, wall shear stress (WSS), oscillatory shear index, spatial and temporal gradient of WSS and their distribution in the target artery were calculated from the flow field. In the wider bypass, the stagnation point oscillated in a greater range and was located more proximal to the anastomosis. Energy dissipation was minimal in a wider bypass with a more acute angle. The maximum WSS values were tree times greater in a narrow bypass and concentrated in a smaller circular region at the floor of the anastomosis. The oscillatory shear index increased with wider bypass and more acute angle. The maximum of spatial gradient of WSS concentrated around the floor and toe of the anastomosis and decreased with more acute angle and wider bypass, the temporal gradient of WSS was stretched more towards the side wall. Greater bypass to target vessel ratio and more acute anastomosis angle promote hemodynamics known to reduce formation of intimal hyperplasia.