Anatomic and Hemodynamic Correlations in Carotid Artery Stenosis

Pressures were measured in the carotid arteries of 61 patients proximal and distal to atherosclerotic plaques which were carefully studied by angiography and anatomical dissection. (1) An atherosclerotic plaque causing a constriction of less than 47% luminal diameter leaving a lumen greater than 3.0 mm in diameter never caused pressure drops of greater than 10 mm Hg. Stenoses of greater than 63% luminal diameter leaving lumens less than 1.0 mm in diameter always caused pressure drops. (2) Atherosclerotic plaques producing defects which narrowed the lumen fell into a distinct pattern: (a) Type 1 lesions-This basic lesion filled the bulb of the internal carotid artery near its origin, causing a 1 to 2 cm smooth elliptical encroachment on the lumen. (b) Type 2 lesions-Short localized areas of thickening in addition to the basic lesion caused bar-like defects of the lumen at the origin of the internal carotid artery or near the distal end of the lesion. (c) Type 3 lesions-Multiple bar-like defects were sometimes seen. (d) Type 4 lesions-The areas of increased thickening of the lesion were sometimes quite narrow, producing diaphragm-like defects on the lumen. Although theoretically these various types of stenoses should produce different hemodynamic changes, insufficient numbers of observations were made to corroborate these presumptions. (3) Angiograms in general mimicked the gross appearance of the plaques and predicted the actual degree of stenosis produced but did not identify many diaphragm defects, ulcerations, or small thrombi.