Date of Award


Degree Type


Degree Name

Doctor of Philosophy


A poststenotic dilatation (PSD) is thought to occur as a result of structural changes in the artery wall, particularly in elastin. The purpose of this study was to quantitate the morphologic changes in the artery wall associated with the development of PSD's, and in particular determine if structural changes occurred in elastin.;The morphology of experimentally produced PSD's in the thoracic aorta of New Zealand white rabbits was studied using histologic, scanning electron microscopic (SEM), and transmission electron microscopic (TEM) techniques, and compared quantitatively to the morphology in the walls of normal aortas.;The fenestration diameter, density, and percent of the internal elastic lamina (IEL) covered by fenestrations were measured from SEM micrographs of the luminal side of the IEL, which had been exposed by sodium hydroxide digestion. The mean fenestration diameter and density from normal aortas was 1.40 {dollar}\mu{dollar}m {dollar}\pm{dollar} 0.03 (SEM) and 2250 fenestrations per mm{dollar}\sp2{dollar} {dollar}\pm{dollar} 161 (SEM) respectively; 0.57% {dollar}\pm{dollar} 0.05 (SEM) of the surface of the IEL being covered by fenestrations. Comparisons using t-test's showed no significant change (p {dollar}>{dollar} 0.101) in fenestration diameter until the dilatations increased beyond 21% at which point mean diameters increased (p {dollar}<{dollar} 0.001) compared to normal aortas. The mean fenestration density was signficantly increased (p {dollar}<{dollar} 0.001) in dilatations up to 21%, but decreased (p {dollar}<{dollar} 0.002) in dilatations greater than 21%. These measurements supported the hypothesis that changes in elastin would be found in the wall of PSD's.;Measurements from histological sections of PSD's showed an increased area of smooth muscle cell (SMC) nuclei, a trend toward thicker artery walls and thicker elastin lamellae as dilatations became larger. Standard stereological techniques applied to TEM micrographs of the tunica media showed a decline in the volume fraction of elastin, while the volume fraction of SMC's increased.;Based on the results of this study a new mechanism for the production of PSD's is proposed, which involves growth of the artery wall and the elastin, as well as the coalescence of fenestrations in the elastic lamellae. These changes represent remodelling of the artery wall resulting in the luminal enlargement characteristic of PSD's.



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