Poststenotic flow velocity changes as a function of stenosis geometry.

We used an in vitro pulsatile flow model to examine the velocity profile distal to a variable nonaxisymmetric stenosis. Using a continuous-wave Doppler velocimeter, the peak systolic frequency was determined distal to the stenosis and in planes parallel and perpendicular to the long axis of the stenosis. In both planes, an exponential regression best describes the relationship between peak systolic frequency and reduction in cross-sectional area. Regressions at each point of insonation diverged as a direct function of reduction in cross-sectional area and as an indirect function of distance from the stenosis. At each point of insonation, regressions representing the relationship in the mutually perpendicular planes diverged in direct proportion to reduction in cross-sectional area. Slopes were greater in parallel planes of insonation. These data demonstrate that two variables, distance and geometry, may influence the results of spectral analytic studies.