Relationship of high-intensity plaques on T1-weighted magnetic resonance imaging with coronary intraplaque hemorrhage: A directional coronary atherectomy study

Background: Although intraplaque hemorrhage (IPH) has been identified as a key feature of rupture-prone plaques, noninvasive imaging-based features for its detection in coronary artery have not been clearly established. The aim of this study was to investigate the relationship of the ratio between the signal intensities of coronary plaque and cardiac muscle (PMR) on non-contrast T1-weighted imaging (T1WI) in magnetic resonance with IPH in the directional coronary atherectomy (DCA) specimens.Methods: Fifteen lesions from 15 patients, who underwent DCA and T1WI, were prospectively enrolled. The snap-frozen samples obtained by DCA were used for immunohistochemical staining against a protein specific to erythrocyte membranes (glycophorin A) and macrophages. The percentage of glycophorin A and macrophages was graded using a scale from 0 to 4, with higher scores indicating higher percentages.Results: PMR showed a strong positive correlation with glycophorin A scores (rho = 0.772, p < 0.001), whreas, there was a weak correlation between the PMR and macrophage scores (rho = 0.626, p < 0.05). The receiver operating characteristic curve analysis showed that the optimal PMR cutoff value for predicting glycophorin A scores >= grade 2 (glycophorin A-positive area >= 5% of the plaque) was 1.2 (area under the curve; 0.91, 95% confidence interval; 0.73-1.00), and this PMR value had a sensitivity of 8/9 (89%), specificity of 6/6 (100%), positive predictive value of 8/8 (100%), and negative predictive value of 6/7 (86%).Conclusions: In patients with ischemic heart disease, a high PMR on T1WI is a predictor of coronary IPH as assessed by DCA specimens.