Spatial orientation of atherosclerotic plaque in non-branching coronary artery segments

It has been postulated that atherosclerotic plaque deposition is spatially related to regions of low shear in non-branching vessel segments. Intravasc ular ultrasound (IVUS) allows precise spatial orientation of coronary arter y plaque formation in humans. The objective of this study was to test the h ypothesis that coronary plaques have a higher prevalence on the myocardial side in regions that encounter low surface shear stress. IVUS allows the de termination of the inner versus the outer curve of the vessel based on vasc ular and perivascular landmarks. We studied 30 consecutive patients pre-int ervention using IVUS and measured vessel area, lumen area and plaque area ( vessel-lumen area) during a motorized pullback at 1 mm intervals. Vessel se gments near a side branch (within two times the diameter of the vessel) wer e excluded from analysis because of flow disturbances. All plaques were cla ssified as concentric or eccentric and all eccentric plaques were further d ivided with respect to their spatial orientation in the vessel into quadran ts: myocardial (inner curve, lower shear stress), epicardial (outer curve, higher shear stress) and lateral (two quadrants intermediate). A total of 6 13 cross-sections were analyzed in 14 left anterior descending, six left ci rcumflex, and ten right coronary arteries. Plaque distribution was found to be concentric in 321 (52.4%) and eccentric in 292 (47.6%) cross sections. Of all eccentric plaques, 184 cross sections were oriented toward the myoca rdial side (62.6%) compared to only 54 toward the epicardial side (17.3%) a nd 54 in the 2 lateral quadrants (19.5%, P < 0.001). No difference in plaqu e area (6.75 +/- 2.70 vs. 6.76 +/- 2.60 mm(2)), vessel area (15.28 +/- 4.73 vs. 15.35 +/- 4.40 mm(2)), or plaque thickness (1.26 +/- 0.37 vs. 1.25 +/- 0.43 mm) was noted between myocardial or epicardial plaques. These results suggest that atherosclerotic plaques develop more frequently on the myocar dial side of the vessel wall, which may relate to lower shear stress. Howev er, plaque size is similar on the epicardial and myocardial side. (C) 2000 Elsevier Science Ireland Ltd. All rights reserved.