Relationship Between Thin Cap Fibroatheroma Identified by Virtual Histology and Angioscopic Yellow Plaque in Quantitative Analysis With Colorimetry

Background: Thin cap fibroatheroma (TCFA) is considered to be a vulnerable plaque. Virtual Histology-intravascular ultrasound (VH-IVUS) can precisely identify TCFA in vivo. Intense yellow plaque on angioscopy determined by quantitative colorimetry with L*a*b* color space corresponds with histological TCFA; in particular, a plaque of color b* value >23 indicates an atheroma with a fibrous cap thickness 10% of plaque area without overlying fibrous tissue, and angioscopic TCFA was a plaque with b* value >23. The frequency of angioscopic TCFA was higher in the VH-TCFA group than in the VH-non-TCFA group (74% vs 23%, P=0.0002). Moreover, yellow color intensity (b* value) significantly correlated with plaque classification on VH-IVUS. When TCFA detected with angioscopy was used as the gold standard, the sensitivity, specificity, and accuracy for TCFA with VH-IVUS was 68%, 81%, and 75%, respectively. Conclusions: VH-TCFA strongly correlated with angioscopic TCFA determined by a quantitative analysis with colorimetry. (Circ J 2009; 73: 497 - 502)