Abstract 2796: Coronary Plaque Classification by Multislice Computed Tomography in Comparison with Histopathological Examination of the Atheromatous Tissue Obtained by Directional Coronary Atherectomy

Abstract

Multislice computed tomography (MSCT) has been reported to characterize plaque morphology using intracoronary ultrasound (ICUS) findings as the reference. However, the histopathological assessment for the efficacy of MSCT to distinguish atherosclerotic coronary plaque components has not been performed in vivo. We sought to find the cutoff values of CT density (CTD) to classify the non-calcified plaques using histopathological findings as the standard of reference. Thirty nine target lesions treated by directional coronary atherectomy (DCA) in 39 patients with coronary artery disease, who underwent preintervention MSCT and ICUS, were investigated. The lesions with calcifications in MSCT were excluded. DCA samples of plaques were histopathologically classified into one of the two types; lipid rich plaque (L) or fibrous plaque (F), and further, these two plaque types were subdivided into each two groups, plaque with calcifications or without (L-C, L-NC, F-C, F-NC). The mean CTD was determined by ROI method (5 ROIs) from three cross-sections of each target lesion. We compared the mean CTD among the groups and determined the best cutoff values to differentiate plaque compositions by receiver operating characteristic (ROC) curve. Sixteen lesions were histopathologically classified as lipid rich (6 with calcification (L-C), 10 without (L-NC)) and 23 lesions as fibrous plaque (11: F-C, 12: F-NC). Although mean CTD was not significantly different among the groups (L-C: 73±28 HU, L-NC: 39±11, F-C: 87±15, F-NC: 70±12, p=0.09), there was a significant difference between L-NC and F-NC (p<0.01). ROC analysis revealed that the best cutoff value to differentiate L from F showed relatively low sensitivity (cutoff value 52HU, sensitivity 69%, specificity 96%, AUC 0.82), whereas very high sensitivity and specificity (cutoff value 44 HU, sensitivity 90%, specificity 100%, AUC 0.97) was detected for the cutoff value to differentiate L-NC from F-NC. Plaque CTD may accurately classify non-calcified plaque compositions comparable to histopathological definitions when the lesions were composed without microscopic calcifications.