Date of Award
Doctor of Philosophy
Two sets of experiments were performed to test the hypothesis that turbulent blood flow distal to a stenosis in an artery vibrated the artery wall causing a poststenotic dilatation (PSD). I developed an in situ flow model to observe vibration distal to a moderate stenosis (a 72 to 88% reduction in cross-sectional area) in the descending thoracic aorta of 10 recently killed dogs. The vessel was perfused with a steady flow of saline over a range of Reynolds numbers (0 to 6000) and distending pressures (70 to 120 mm Hg). Vibration was measured with a non-contacting fiber optic device, and pressure fluctuations with a catheter-tip manometer. Measurements were made in situ, and then the vessel was excised, mounted in a tissue bath, and the measurements repeated in vitro.;The artery behaved similiarly in situ and in vitro, vibrating over a range of frequencies between 0 and 600 Hz, with a maximum amplitude of 67 to 157 (mu)m or 1.3% to 2.7% strain. Damping was the same in situ as in vitro. Fourier analysis of the vibration identified two or three resonant frequencies corresponding to circumferential and longitudinal modes of vibration. Thirteen out of thirty-five of these frequencies were sensitive to the distending pressure, increasing in frequency 0.3 to 1.0 Hz/mm Hg.;In vitro experiments were then performed to determine whether wall vibration alone can create a PSD, defined as an enlargement of the vessel with an increase in its distensibility, and an enlargement of the fenestrations in its internal elastic lamella. Eight segments of dog carotid artery, mounted in a tissue bath at in vivo length and inflated to 100 mm Hg, were vibrated at one frequency between 81 and 585 Hz with an amplitude between 1.0% and 6.9%. After eight hours, the average vessel diameter was significantly greater than for non-vibrated control arteries, but no changes were observed in the mechanical or morphological properties. In these experiments, therefore, in vitro vibration did not produce a PSD, suggesting that although vibration can occur distal to a stenosis, its presence alone is insufficient to cause a PSD.
Lillie, Margo Alan, "Vibration Of The Arterial Wall As A Cause Of Poststenotic Dilatation" (1986). Digitized Theses. 1551.