ObjectivesThe present study aimed to determine characteristics of macrophage accumulation and predictors of CD163 positive macrophages by ultrasonic tissue characterization.BackgroundIntraplaque hemorrhage is associated with plaque instability and induces macrophage accumulation with a scavenger receptor, CD163. These CD163 positive macrophages have anti‐atherogenic property.MethodsIn 50 patients with acute coronary syndrome, lumen, vessel and plaque area, and plaque components (% fibrous, % fibro fatty, % dense calcium, and % necrotic core) of the culprit lesion were determined by virtual histology (VH) intravascular ultrasound (IVUS). Remodeling index (RI) was also determined. Atherothrombotic debris of the culprit lesion was collected during percutaneous coronary intervention using a distal protection device. CD163 positive macrophages and glycophorin A (a protein specific to erythrocytes) were determined immunohistochemically.ResultsPercentage of CD163 positive macrophages to the whole cells (% CD163) correlated positively with lumen, vessel and plaque area, and RI. Further, % CD163 had significant positive correlation with % necrotic core and negative correlation with % dense calcium. Immunopositive areas of glycophorin A (% glycophorin A), expressed as the ratio of positively stained areas per total tissue, had a significant positive correlation with % CD163. On multivariate analysis, % necrotic core, % dense calcium, and RI were independent determinants of % CD163.ConclusionPositive remodeling and large necrotic core without calcification on VH‐IVUS were likely to indicate coronary intraplaque hemorrhage with CD163 positive macrophages infiltration. (J Interven Cardiol 2014;27:317–324)