LUMEN AND PLAQUE SHAPE IN ATHEROSCLEROTIC CORONARY-ARTERIES ASSESSED BY IN-VIVO INTRACORONARY ULTRASOUND

Current knowledge of lumen and plaque shape of atherosclerotic coronar y vessels is derived from in vitro examination of coronary vessels. Th e in vivo plaque and lumen shape was studied by intracoronary ultrasou nd (ICUS) imaging in 82 patients with coronary artery disease and the images were analyzed by computerized morphometry. In 386 of the 638 cr oss sections (61%) with atherosclerotic plaque, nondiseased wall (inti ma thickness <200 mu m) was present in the ions image; in 440 sections (69%), the plaque was located eccentrically in the vessel. Although t he extent of nondiseased wall segment and eccentricity decreased with plaque burden, 42% of cross sections with plaque stenosis >60% had res idual nondiseased wall, and 40% of these cross sections showed eccentr ic plaque. A circular or near-circular lumen (ratio of long/short diam eter <1.1) was found in 252 cross sections (39%), an elliptical lumen in 370 (58%), and a ''D''-shaped lumen in 16 cross sections (3%); slit - or star-like lumen shapes were not detected. The ratio of long/short diameter was lower in the 555 noncalcified (1.10 +/- 0.08) than in th e 83 calcified cross sections (1.15 +/- 0.08; p <0.001). Radiographic lumen area measurements were simulated in ellipse models based On the long and short lumen axes measured in the ICUS images. Assuming a sing le radiographic view, maximal over- or underestimation of up to 40% co mpared with the true vessel lumen is possible. Errors in lumen area me asurements increased with plaque area stenosis, reflecting the more el liptical lumen shape in advanced coronary disease. When biplane orthog onal views on the lumen silhouette are used, the maximal error for lum en area measurements occurs at a 45 degrees angle to the long lumen ax is. In all cross sections, the maximal error for lumen area measuremen ts with biplane radiographic views resulted in an error <10% as compar ed with true vessel lumen. Thus, the present in vivo observations conf irm previous histologic findings that eccentric plaque and residual no ndiseased wall may be found even in advanced coronary atherosclerosis. In contrast to histologic findings, the lumen shape of atheroscleroti c coronary vessels deviates only moderately from a circular lumen. Rad iographic lumen area measurements in coronary vessels are therefore on ly slightly affected by different lumen shapes when biplane views are used.