Abstract 4408: Optical Coherence Tomographic Findings of Macrophage Accumulation in Atherosclerotic Lesions
[Introduction] The impact of early vulnerable plaque detection and therapy would be a major breakthrough in the management of patients with coronary, peripheral and neurovascular disease. The vulnerable plaque is characterized by thin fibrous cap, large lipid core and dense macrophages accumulation. Optical coherence tomography (OCT) allows vessel cross-sectional imaging with a resolution of nearly 10 micrometer, and made precise measurement of the thickness of the fibrous cap possible. However, there is no visual criteria for the OCT detection of macrophage accumulation. The aim of this study was to establish an objective, and visual OCT image criteria for detection of macrophage accumulation within atherosclerotic lesions.
[Method] Iliac arteries and aortas of the WHHLMI rabbits (n=5), 1%-(n=4) and 0.3%-(n=6) cholesterol diet-loaded JW rabbits were observed with OCT. After OCT, arteries were harvested for histology with HE, EVG, and Masson trichrome stains, and for immunoperoxidase staining with RAM11 for macrophage detection. Precise correspondence of histology and OCT images was identified in 133 sections. We hypothesized that aggregated high intensity signal followed by stripe pattern shadow (’OCT macrophage criteria’) indicates macrophage accumulation.
[Result] On OCT observation, there were 28 ’OCT macrophage criteria’ positive lesions. All of these 28 lesions always exhibited >=2 cell-layers of macrophage accumulation in histology (positive predictive value=100%). Inversely, in histology, there were 35 lesions with >=2 cell-layers of macrophage accumulation, indicating the sensitivity of the criteria as 80%. In these 7 OCT false negative lesions, absence of the ’OCT macrophage criteria’ findings may be due to the increase in the distance between the lesions and the image wire. On the other hand, specificity of the ’OCT macrophage criteria’ was 100%(98/98). However, macrophages of smaller amount (<<26>1 cell-layer of macrophage) or foam cells deep-seated in the lipid-pool were difficult to detect.
[Conclusion] The OCT finding of high intensity signal with stripe pattern shadow indicates macrophage accumulation in atherosclerotic lesions.