In vivo characterization of coronary plaques: novel findings from comparing greyscale and virtual histology intravascular ultrasound and near-infrared spectroscopy.

AIMS To test the hypothesis that near-infrared spectroscopy (NIRS) combined with intravascular ultrasound (IVUS) would provide novel information of human coronary plaque characterization. METHODS AND RESULTS Greyscale-IVUS, virtual histology (VH)-IVUS, and NIRS were compared in 131 native lesions (66 vessels) that were interrogated during catheterization by all three modalities. Greyscale-IVUS detected attenuated and echolucent plaques correlated with NIRS-detected lipid-rich areas. Attenuated plaques contained the highest NIRS probability of lipid core, followed by echolucent plaques. By VH-IVUS, 93.5% of attenuated plaques contained confluent necrotic core (NC) and were classified as VH-derived fibroatheromas (FAs). Although 75.0% of echolucent plaques were classified as VH-FAs, VH-NC was seen surrounding an echolucent zone, but not within any echolucent zone; and echolucent zones themselves contained fibrofatty and/or fibrous tissue. All calcified plaques with arc >90° contained >10% VH-NC (range 16.0-41.2%) and were classified as calcified VH-FAs, but only 58.5% contained NIRS-detected lipid core. A positive relationship between VH-derived %NC and NIRS-derived lipid core burden index was found in non-calcified plaques, but not in calcified plaques. CONCLUSION Combining NIRS with IVUS contributes to the understanding of plaque characterization in vivo. Further studies are warranted to determine whether combining NIRS and IVUS will contribute to the assessment of high-risk plaques to predict outcomes in patients with coronary artery disease.