Hemodynamics of endovascular prostheses.

A surgical study (Bergeron et al., 1991, International Angiology 10(3), 182-186) picked out that re-endothelialization of implanted expandable stents, frequently used to reduce the recurrent stenosis rate after balloon angioplasty, was correct and more rapid in femoro-popliteal arteries (quasi-straight vessels) than in iliac arteries (bifurcated vessels). Since it is now well known that local hemodynamics are considered to be an important atherogenic factor, we decided to compare and optimize the shape of the existing equipment, in order to further give some informations to surgeons about the optimal stenting at the site of bifurcation. Therefore, we studied in vitro (1) the influence of the protruding part of a stent on the flow patterns in the branches of an aorto-iliac bifurcation model, and (2) the possibility of reducing or preventing this impact. Qualitative information was obtained from visualizations in the horizontal median plane of the bifurcation model, while Doppler ultrasonic velocimetry provided quantitative data, at different points of the cardiac cycle. Results showed that a standard stent implanted in a daughter branch of the bifurcation may have a considerable influence on flow behaviour when it is sticking out of the daughter branch. A new design of stent, with a bevelled shape, showed a significant reduction of flow disturbance.