T J Psyhojos | PubMed Health

PubMed1987

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.

Arterial Occlusive Diseases↗

PubMed1986

Doppler-derived percentage systolic window and the quantitation of arterial stenosis.

Peak systolic frequency (PSF) and percentage systolic window (%SW) are spectral parameters used to characterize poststenotic flow velocity patterns. The PSF, obtained using a continuous-wave (CW) Doppler velocimeter, has been used more frequently, however, in the quantitation of carotid occlusive disease. The authors have employed a microprocessor-driven pulsatile flow model to evaluate more completely the relationship between stenosis and the %SW. Using an 8 MHz CW Doppler probe, the Doppler-shifted frequencies were recorded at 1, 2, 3, 4, and 5 diameters distal to a variable, nonaxisymmetric stenosis, which reduced the cross-sectional area (CSA) 25, 40, 50, 60, 70, 85, and 97 per cent. Four sets of observations were made and the %SW derived using a spectrum analyzer. At one diameter from the stenosis, the relationship between the %SW (Y) and the reduction in CSA (X) is best described by two first-order regressions (Y = MX + B). The slope of the relationship from 0 to 60 per cent reduction in CSA is nearly flat, -0.052, while there is a significant (P less than 0.05) decrease in the slope, -1.538, when the CSA is further reduced from 60 to 97 per cent. Beyond 1 diameter, the relationship is best described by a single linear regression, the gradual slope of which does not permit clinically useful comparisons. These data explain the lack of strong correlation between CSA and %SW when the data are evaluated over the entire range of stenoses. However, they do indicate that the %SW may be a useful correlate if it is obtained within one diameter of the stenosis.

Arterial Occlusive Diseases↗