Thickness, taper, and ellipticity in the aortoiliac bifurcation of patients aged 1 day to 76 years

Lumen area, ellipticity, and wall thickness were measured in the aortoiliac bifurcations obtained at autopsy from 14 patients aged between 1 day and 7 6 years. The method involved freezing pressure-fixed, stained bifurcations on the stage of a refrigerated microtome and then looking at the block face while sections were removed. Area change was normalized over segment lengt h to produce a value of either taper (narrowing, in mm(2)/mm), or flare (ex pansion). The aortoiliac bifurcations were divided into three regions based on the area changes: an apical region corresponding to the bifurcation ape x (taper = 2.96 +/- 0.80 mm(2)/mm), a preapical region (flare = 3.58 +/- 0. 87 mm(2)/mm), and the postapical region (flare = 0.82 +/- 0.80 mm(2)/mm). P reapical lumen ellipticity showed that the anterioposterior diameter was al ways less than the lateral diameter, while the degree of ellipticity increa sed with age. Average circumferential wall thickness, assessed in polar coo rdinates, decreased between 0 degrees (right lateral) and 120 degrees, whil e a significant increase in wall thickness was present between 120 degrees and 200 degrees. The most striking difference was found in the 1-day-old, w hich was very thin posteriorly. This detailed geometric analysis of the aor toiliac bifurcation suggests that taper, hare, and variations in both circu mferential and longitudinal wall thickness need to be considered when tryin g to correlate physical factors in the aorta with the precise location of a therosclerotic lesions and wall remodeling.