Optimising Miller cuff dimensions. The influence of geometry on anastomotic flow patterns

Objectives: since cuff dimensions are variable, we studied the influence of cuff geometry on flow mechanics, in an attempt to identify the optimum con figuration. Materials and methods: bench studies involved the manufacture of anatomical ly accurate models of varying cuff dimensions, perfused in a specifically d esigned flow rig, simulating physiological conditions. Flow visualisation s tudies incorporating laser illumination of tracer particles enabled accurat e analysis of flow patterns. Results: the vortex created within the proximal cuff of each model during t he decleration phase of the cardiac cycle was strongly influenced by the as pect ratio (AR = cuff height:length). The standard and high cuffs (AR = 1.6 3 and 1.18, respectively) demonstrated cohesive vortices and stable flow pa tterns. Low and long cuffs (AR = 2.6 and 2.25, respectively) created more c omplex vortices with large areas of flow separation and low velocities. Conclusions: aspect ratio has an important influence on flow within the dis tal anastomosis, with cuff dimensions of 13 mm long and 8-11 mm high (stand ard and high cuffs) creating beneficial flow patterns anticipated to optimi se wall shear stress and inhibit myointimal hyperplasia.