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

Current knowledge of lumen and plaque shape of atherosclerotic coronary vessels is derived from in vitro examination of coronary vessels. The in vivo plaque and lumen shape was studied by intracoronary ultrasound (ICUS) imaging in 82 patients with coronary artery disease and the images were analyzed by computerized morphometry. In 386 of the 638 cross sections (61%) with atherosclerotic plaque, nondiseased wall (intima thickness <200 mu m) was present in the ions image; in 440 sections (69%), the plaque was located eccentrically in the vessel. Although the extent of nondiseased wall segment and eccentricity decreased with plaque burden, 42% of cross sections with plaque stenosis >60% had residual nondiseased wall, and 40% of these cross sections showed eccentric plaque. A circular or near-circular lumen (ratio of long/short diameter <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 the 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 single radiographic view, maximal over- or underestimation of up to 40% compared with the true vessel lumen is possible. Errors in lumen area measurements increased with plaque area stenosis, reflecting the more elliptical lumen shape in advanced coronary disease. When biplane orthogonal views on the lumen silhouette are used, the maximal error for lumen area measurements occurs at a 45 degrees angle to the long lumen axis. In all cross sections, the maximal error for lumen area measurements with biplane radiographic views resulted in an error <10% as compared with true vessel lumen. Thus, the present in vivo observations confirm previous histologic findings that eccentric plaque and residual nondiseased wall may be found even in advanced coronary atherosclerosis. In contrast to histologic findings, the lumen shape of atherosclerotic coronary vessels deviates only moderately from a circular lumen. Radiographic lumen area measurements in coronary vessels are therefore only slightly affected by different lumen shapes when biplane views are used.