Evidence of a possible link between poststenotic dilation and wall shear stress

The effects of an axisymmetric 65% area reduction stenosis on a pulsatile flow were investigated by use of an in vitro model that permits simultaneous visualization of the flow velocity profiles at seven sites. By use of seven lenses to focus the ultraviolet light from a nitrogen laser, seven thin blue lines were produced in the photochromic solution flowing through the tube. The displacement profiles of the dye traces were photographed, resulting in the acquisition of the velocity profiles. From these traces, the flow pattern was determined, and the wall shear stresses were measured. Turbulence was generated 3.3 to 6.5 tube diameters downstream from the edge of the stenosis, depending on the time in the pulsatile flow cycle. Maximum wall shear stress fluctuations between positive and negative values appeared to lie within 1.6 to 3.3 tube diameters downstream of the stenosis. In several illustrative clinical cases of thoracic outlet arterial compression, the poststenotic dilation was maximum at 2.0 +/- 0.3 vessel diameters downstream. Based on these observations, it is postulated that wall shear stress fluctuations may be important in the development of poststenotic dilation.