OBJECTIVEWe aimed to assess and compare the morphological characteristics of ostial and non-ostial left main coronary artery (LMCA) lesion without heavy calcification using intravascular ultrasound (IVUS) imaging.

METHODSBetween Oct. 2004 and Oct. 2007, 153 patients with confirmed or suspected coronary artery narrowing in coronary angiography with satisfactory IVUS images and non-heavy calcification were included in the study (ostial lesions, n = 47; non-ostial lesion, n = 106). IVUS analysis included plaque composition, external elastic membrane (EEM), lumen, plaque cross-sectional area (CSA), plaque burden (plaque CSA/EEM CSA) at the lesion, proximal and/or distal reference site, and remodeling index (RI, lesion EEM CSA/reference EEM CSA). Negative remodeling was defined as RI < 0.95.

RESULTSLMCA mean reference lumen and vessel diameter was 4.1 +/- 0.8 mm and 5.3 +/- 0.8 mm respectively. Incidence of patients with minimum lumen area (MLA < 6.0 mm(2)) was similar between the two groups (29.5% for ostial lesions and 31.9% for non-ostial lesions, P = 0.87). There were significantly more fibrous (70.2% vs. 35.8%) and soft (8.5% vs. 3.8%) plaques while significantly less calcified plaque (19.2% vs. 43.4%) in patients with hostile lesions compared those with non-ostial lesions (all P < 0.05). Compared to non-ostial lesions, ostial lesion had significant smaller plaque area [(10.8 +/- 4.5) mm(2) vs. (13.3 +/- 5.4) mm(2), P = 0.007], less plaque burden (54.8% +/- 15.9% vs. 61.9% +/- 14.5%, P = 0.020), smaller RI (0.9 +/- 0.2 vs. 1.0 +/- 0.2, P = 0.000) and higher incidence of negative remodeling (74.5% vs. 34.9%, P = 0.000). Multivariant Logistic regression analysis showed that the site of lesion (ostial or non-ostial lesion, OR = 4.9, P = 0.004), plaque area (OR = 1.2, P = 0.01) and plaque burden (OR = 0.003, P = 0.000) were the independent predictors of LMCA remodeling.

CONCLUSIONNegative remodeling might be responsible for the development of LMCA ostial narrowing.