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 configuration. Materials and methods: bench studies involved the manufacture of anatomically accurate models of varying cuff dimensions, perfused in a specifically designed flow rig, simulating physiological conditions. Flow visualisation studies incorporating laser illumination of tracer particles enabled accurate analysis of flow patterns. Results: the vortex created within the proximal cuff of each model during the decleration phase of the cardiac cycle was strongly influenced by the aspect ratio (AR = cuff height:length). The standard and high cuffs (AR = 1.63 and 1.18, respectively) demonstrated cohesive vortices and stable flow patterns. Low and long cuffs (AR = 2.6 and 2.25, respectively) created more complex vortices with large areas of flow separation and low velocities. Conclusions: aspect ratio has an important influence on flow within the distal anastomosis, with cuff dimensions of 13 mm long and 8-11 mm high (standard and high cuffs) creating beneficial flow patterns anticipated to optimise wall shear stress and inhibit myointimal hyperplasia.