Laser-Doppler-anemometry studies of flow behavior in rigid and elastic varicose vein models.

Flow behavior and velocity were studied in six varicose vein models with simulated arteriovenous anastomoses (AVAs). Experiments were performed to determine whether incoming flow entering from AV-anastomoses or small feeder veins could create either small jet streams or velocity fluctuation, which might then cause veins to bulge and get tortuous. Flow was analyzed in areas of flow change. Studies were performed in rigid Plexiglas and elastic, silicon rubber models that exactly replicated the geometry and compliance of varicose veins. Flow was visualized with dyes for steady flow and with a birefringent solution for pulsatile flow studies. Local velocity was measured with a laser-Doppler-anemometer (LDA). Very low forces and shear stresses were found on the interior wall opposite the entrance of the simulated AV anastomoses. However, these values were ten times that of an idealized flow in a straight tube without added flow from simulated AV anastomoses.