In vivo detection of lipid-rich plaque by using a 40-MHz intravascular ultrasound: a comparison with optical coherence tomography findings.

iMAP™ has recently been introduced as a new tissue characterization method using the 40-MHz intravascular ultrasound (IVUS). However, few data have been published on the comparative findings of other imaging modalities in vivo. We examined 108 matched lesions from 70 patients (35 with stable angina and 35 with acute coronary syndrome) that underwent percutaneous coronary intervention (PCI) using pre-PCI OCT and IVUS. Identification of OCT-derived lipid-rich plaques and thin-cap fibroatheroma (TCFA) was performed using iMAP™. OCT-derived lipid-rich plaques and TCFAs were detected in 56 (51.8 %) and 20 (18.6 %) lesions, respectively. The iMAP™ analysis identified significantly greater percentage of necrotic area (%NA) in the lesions with lipid-rich plaques than in those without [46.5 (29.4-56.9) vs. 24.6 (10.3-41.6) %, p < 0.01]. In the receiver operating characteristic (ROC) analysis, the optimal %NA cut-off value for identifying lipid-rich plaques was 33 % (AUC: 0.75; sensitivity: 73.2 %; specificity: 67.3 %). A greater plaque burden and a larger necrotic area were detected using iMAP™ in the OCT-derived TCFAs than in the non-TCFAs [81.5 (77.3-86.8) vs. 72.7 (60.6-81.0) %, p < 0.01; 7.6 (4.3-9.6) mm(2) vs. 2.7 (1.0-6.0) mm(2), p < 0.01]. For the iMAP™-derived TCFAs, combinations of variables such as necrotic area, % plaque burden, and absolute plaque area showed a relatively low positive predictive value and high negative predictive value (plaque burden >75 % and confluent luminal necrotic area >4.0 mm(2); sensitivity: 75.0 %; specificity: 71.6 %; PPV: 37.5 %; NPV: 92.6 %; and diagnostic accuracy: 72.2 %). The results showed that iMAP™ tissue characterization may help to detect lipid-rich plaque and rule out TCFAs in vivo.