In vivo evaluation of fibrous cap thickness by optical coherence tomography for positive remodeling and low-attenuation plaques assessed by computed tomography angiography

Background Coronary plaques with positive remodeling (PR) and low-attenuation plaques (LAP) by computed tomography angiography (CTA) might be associated with plaque vulnerability. The purpose of this study was to assess the relation between coronary plaques with PR and LAP by CTA and fibrous cap thickness measured by optical coherence tomography (OCT). Methods We used CTA and OCT to assess 102 coronary plaques in patients with coronary artery disease (unstable angina pectoris, n = 24; stable angina pectoris, n = 78). Plaque characteristics were divided into three groups: 2-feature-positive plaques (PR and LAP; n = 32), 1-feature-positive plaques (PR or LAP; n = 20), and 2-feature-negative plaques (neither PR nor LAP; n = 50). PR was defined as remodeling index (RI) of >1.05 and LAP was defined as CT density value <50 HU. Results There were significant differences between the three plaque groups with respect to fibrous cap thickness measured by OCT: 76 ± 24 μm in 2-feature-positive plaques, 154 ± 51 μm in 1-feature-positive plaques, and 192 ± 49 μm in 2-feature-negative plaques (P < 0.001). The RI (1.21 ± 0.06, 1.14 ± 0.05, P = 0.011) and the presence of thin cap fibroatheroma (TCFA) (<70-μm thickness) (75%, 15%, P = 0.001) were significantly higher in UAP than in SAP patients with 2-feature-positive plaques, whereas fibrous cap thickness (68.9 ± 24.1, 92.1 ± 21.9 μm, P < 0.001) was lower in the UAP patients. In UAP patients, the presence of ring-like enhancement showed higher accuracy of 88% for detection of TCFA. Conclusions Coronary PR and LAP by CTA were associated with the degree of fibrous cap thickness measured by OCT. CTA can non-invasively provide promising information on plaque vulnerability by identifying coronary plaque with PR and LAP, especially ring-like enhancement.