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 microns) was present in the ICUS 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.(ABSTRACT TRUNCATED AT 250 WORDS)