Vascular bypass surgery is commonly performed in the lower limb network in symptomatic patients presenting arterial occlusions. These bypasses can be performed with prosthetic material (PTFE/ polyester) of different diameters, or with autologous veins. Venous grafts have shown a better long-term patency (persisting graft function) than prosthetic ones (70% versus 40% at 4 years)(1). One hypothesis is an abnormal hemodynamic into the bypass leading to thrombosis or intimal hyperplasia. Nowadays, no objective tool is available to help the surgeon to predict the patient-specific hemodynamic performance of a bypass and choose its most adequate characteristics (material, diameter).

In order to analyse the hemodynamic parameters of the lower limb pathological arterial network before surgery, non-invasive measurement techniques are used: area, velocity and flow rate are recorded by doppler ultrasound; pressure and pulse wave velocity by SphygmoCorÒ. These measurements allow the evaluation of the outflow conditions of the leg (resistance and compliance) and their physiological behaviour related to the bypass. The hemodynamic modification due to the bypass is measured during surgery by invasive techniques: needle technique and Radi PressureWireÒ for the pressure waves and ultrasound flowprobes for the flow rate curves.

These data are included in a numerical model which aim to predict the flow rate expected in the bypass depending on its characteristics of material and diameter. The results are compared to those of published studies describing velocity and flow rate data predictive of early graft failure (1).