Modeling of Competitive Flow in Aortofemoral Bypass

Abstract

Competitive flow places surgical bypasses at risk for thrombosis in certain vascular beds, such as coronary bypass. However, the anatomic configurations that may lead to flow stagnation in aortofemoral bypass remain poorly characterized. We aimed to model competitive flow and determine parameters placing bypass patency at risk. We created an aortofemoral bypass flow dynamics computer model using MATLAB software (MathWorks). Our standard model (Fig 1) included a native iliac artery of 8 mm diameter with patent superficial femoral artery (SFA, 6 mm) and profunda femoris artery (4 mm) outflow and bypass conduit (8 mm) positioned over the profunda femoris artery. Models included native iliac stenosis ranging from 0% to 100% across four time points throughout the arterial impulse cycle. Sensitivity analyses were performed for SFA and profunda femoris arterial occlusion as well as varying arterial and graft diameters. We created a total of 40 models. Fig 2 shows our base model with increasing severity of stenosis. As the severity of native iliac stenosis increases, the arterial impulse in the graft arrives more briskly. With little or no native iliac stenosis, the arterial impulse in the graft limb is delayed, but stagnation of flow does not occur as shown by the aqua coloration moving through the graft limb across time points. Sensitivity analyses demonstrated similar findings. No model demonstrated stagnation of flow portending high risk of bypass graft or native arterial thrombosis. Computer modeling did not demonstrate flow stagnation in aortofemoral bypass across a range of anatomic configurations. Our models suggest that competitive flow of a native iliac artery may not put the bypass graft at risk of flow stagnation and thrombosis.Fig 2Flow dynamics of aortofemoral bypass overlying the profunda femoris artery with increasing stenosis of the native iliac inflow artery across four time points of arterial impulse.View Large Image Figure ViewerDownload Hi-res image Download (PPT)