Histopathological correlates of the napkin-ring sign plaque in coronary CT angiography

ObjectiveThe purpose of this study was to identify histologic characteristics of advanced coronary atherosclerotic plaques that are related with the detection of the napkin-ring sign (NRS) in coronary CT angiography (CCTA).MethodsCCTA was performed in 7 human donor hearts. Histological slicing and stainings were performed in 1 mm increments of each major coronary artery. Histology was co-registered with the CT-data and classified according to the modified AHA classification.ResultsAdvanced plaques (types IV-VI) were present in 139 (23%) of 611 cross sections. Of these 33 (24%) demonstrated an NRS in CCTA. NRS plaques were associated with greater non-core plaque area (median 10.2 vs. 6.4 mm2, p < 0.01) and larger vessel area (median 17.1 vs. 13.0 mm2, p < 0.01). The area of the necrotic/lipid core was larger in plaques with NRS (median 1.1 vs. 0.5 mm2, p = 0.05). Angiogenesis tended to be more frequent in plaques with NRS (48% vs. 30%) whereas micro-calcifications tended to be more frequent in plaques without NRS (27% vs. 46%) (p = 0.06 and 0.07 respectively). In a multivariate analysis, necrotic/lipid core area (OR = 1.9), non-core plaque area (OR = 1.6), and total vessel area (OR = 0.9) independently predicted the appearance of the NRS in coronary CT angiography.ConclusionDelineation of NRS in CCTA is independently linked to the size of the necrotic/lipid core, the size of the non-core plaque and to the vessel area as measured in histology of advanced coronary atherosclerotic plaques.

▸ Ex-vivo coronary arteries from 7 hearts were images using high resolution CT angiography. ▸ Images were co-registered with histology. ▸ Plaques with a napkin ring sign (NRS) in CT showed a larger necrotic core area than plaques without NRS. ▸ Neovascularization tended to be more common in plaques with NRS.