Combined NIRS and IVUS imaging detects vulnerable plaque using a single catheter system: a head-to-head comparison with OCT.

AIMS: The presence of thin-cap fibroatheromas (TCFA) is associated with high risk of acute coronary syndrome, hence their early detection may identify high-risk patients. In the present study we investigated the ability of a combined imaging catheter with near-infrared spectroscopy (NIRS) plus intravascular ultrasound (IVUS) to detect TCFA in patients with stable coronary artery disease.

METHODS AND RESULTS: Optical coherence tomography (OCT) and combined NIRS-IVUS assessment were performed on identical coronary segments. IVUS analysis provided per-segment minimal cross-sectional area (CSA), plaque length (PL), plaque burden (PB), plaque volume (PV), and remodelling index (RI). OCT was used as the gold-standard reference to define TCFA (fibrous cap thickness <65 μm). Plaque lipid content was estimated by NIRS (lipid core burden index [LCBI]). OCT-defined TCFA was present in 18 of 76 segments. IVUS revealed that OCT-defined TCFA were positively remodelled lesions with greater PB and PV, smaller CSA, and longer PL, while NIRS revealed greater LCBI per 2 mm segment (LCBI2mm) (all p<0.001). Greatest accuracy for OCT-defined TCFA detection was achieved using LCBI2mm >315 with RI >1.046 as a combined criterion value.

CONCLUSIONS: OCT-defined TCFA are characterised by positive vessel remodelling, high plaque burden and greater lipid core burden as assessed by dual NIRS-IVUS imaging.