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The effects of the geometry of a stenosis on poststenotic flow in models and poststenotic vibration of canine carotid arteries in vivo

1980; Elsevier BV; Volume: 13; Issue: 7 Linguagem: Inglês

10.1016/0021-9290(80)90062-7

1873-2380

Margot R. Roach, Douglas Stockley,

Cerebrovascular and Carotid Artery Diseases

The size of the turbulent zone downstream from a stenosis was investigated under steady flow conditions with tube Reynolds numbers (Re) of 300–700. Dye was injected proximal and distal to the stenosis, and dispersion of the dye used as an indication of turbulence. The length of the jet increased linearly as the diameter of the stenosis increased, but the slope was altered from 13.5 ± 1.0 to 19.9 ± 1.1 as the length of the stenosis was altered from 0.105 to 2.1 tube diameters. The diameters of the stenoses varied from 0.2 to 0.8 tube diameters. These slopes had a linear correlation coefficient of 0.98 with p < 0.01. The total length of the turbulent zone was a minimum with stenoses of about 0.45 tube diameters, and the relationship was nonlinear. Changing the Re from 300 to 700 had little effect. Comparable stenoses were created in six carotid arteries in three dogs by clamping machined plexiglass stenoses of two lengths (0.2 and 2.5 cm) over the arteries. The degree of stenosis was determined histologically from the stenosed, pressure-fixed arteries. Flow, measured with an electromagnetic flowmeter proximal to the stenosis, decreased as the diameter of the stenosis decreased or as its length increased. Vibration of the artery was measured with a phonocatheter placed on the arterial wall. The total length of the turbulent zone (measured as wall vibration) was greater for tight stenoses, and also for short ones, although the very tight ones had little vibration. With non-critical stenoses (i.e. ones that did not reduce flow), the peak frequency did not appear to vary with the degree of stenosis. The highest frequencies occurred at 47% stenosis by diameter. No resonant frequencies were observed. The log of the area under the fractional energy curve (i.e. ∫ A2(f)·f2 where A(f) is the amplitude and f the frequency) varied inversely with the stenosis diameter. The results do not explain the inverse correlation between the length of the poststenotic dilatation and the diameter of renal arterial stenoses observed previously. They suggest that transmission of vibration in the wall may be more important than the length of flow disturbance.