Limitations of OCT in identifying and quantifying lipid components: an in vivo comparison study with IVUS-NIRS.

AIMS: We aimed to assess the agreement between IVUS-NIRS and OCT to assess lipid plaques in patients with acute coronary syndromes or stable angina. In addition, the impact of both macrophages and calcifications was investigated.

METHODS AND RESULTS: Forty-three patients undergoing both IVUS-NIRS and OCT assessment of the culprit and/or non-culprit coronary lesions were enrolled. Cross-sections from lipid plaques, calcified plaques and normal-appearing vessel tracts were identified and matched with the two imaging techniques. Lipid arc was measured by both IVUS-NIRS and OCT. Macrophage presence and calcifications were also investigated with OCT. OCT detected a lipid plaque in 90 cross-sections (48.9%), with a sensitivity of 85.5% and a specificity of 69.7% as compared with IVUS-NIRS. The percentage of OCT false positive was 20.1% and of false negative was 4.9% for lipid plaque detection. The Pearson correlation coefficient for lipid arc was 0.675, p=0.0001. Macrophages were detected in 73% of OCT false positive cross-sections. Conversely, calcifications were present in 66.7% of OCT false negative cross-sections. The variability of lipid arc was independently associated with macrophages (beta=0.295, p=0.013).

CONCLUSIONS: Agreement between IVUS-NIRS and OCT for lipid plaque detection is suboptimal. The presence of macrophages and superficial calcifications on OCT negatively affects lipid detection.