Implication of Plaque Color Classification for Assessing Plaque Vulnerability: A Coronary Angioscopy and Optical Coherence Tomography Investigation

ObjectivesThe purpose of this study was to assess the relationship between plaque color evaluated by coronary angioscopy and fibrous cap thickness estimated by optical coherence tomography (OCT) in vivo.BackgroundYellow color intensity of coronary plaque evaluated by coronary angioscopy might be associated with plaque vulnerability.MethodsSeventy-seven coronary artery plaques in patients with acute coronary syndrome were observed by angioscopy and OCT. Plaque color was graded as white, light yellow, yellow, or intensive yellow.ResultsThere were significant differences among the groups classified by plaque color with respect to the fibrous cap thickness estimated by OCT: 389 ± 74 μm in white plaques, 228 ± 51 μm in light yellow plaques, 115 ± 28 μm in yellow plaques, and 59 ± 14 μm in intensive yellow plaques (p < 0.0001). In Spearman rank-order correlation analysis, there was a significant negative correlation between yellow color intensity and fibrous cap thickness (p < 0.0001). Furthermore, 80% of intensive yellow plaques were thin cap fibroatheroma with a cap thickness of ≤65 μm.ConclusionsThe plaque color in coronary angioscopy was determined by the fibrous cap thickness, which was assessed by OCT. Although coronary angioscopy remains a specialized research tool, it might allow us to evaluate plaque vulnerability.