iMap-Intravascular Ultrasound Radiofrequency Signal Analysis Reflects Plaque Components of Optical Coherence Tomography-Derived Thin-Cap Fibroatheroma.

Background: The ability of iMap-intravascular ultrasound (IVUS) tissue characterization to detect thin-cap fibroatheroma (TCFA) identified on optical coherence tomography (OCT) has not yet been fully elucidated.

Methods and results: We evaluated 86 coronary lesions from 73 patients with stable angina pectoris using iMap-IVUS and OCT. We defined OCT-derived TCFA (OCT-TCFA) as lipid-rich plaque with a <65-μm-thick fibrous cap. The external elastic membrane (EEM) cross-sectional area (CSA), lumen CSA, plaque plus media (P+M) CSA, plaque burden and remodeling index were measured on gray-scale IVUS. Plaque components categorized on iMap-IVUS as fibrotic, lipidic, necrotic or calcified are presented as absolute area and proportion (%) of total plaque area. OCT-TCFA (22 lesions) had significantly greater EEM CSA, P+M CSA, plaque burden and remodeling index than non-TCFA (64 lesions). Significantly larger %necrotic area, absolute lipidic and necrotic areas and smaller %fibrotic areas were found in OCT-TCFA than in non-TCFA. On multivariate analysis, absolute necrotic area was an independent predictor of OCT-TCFA. The area under the ROC curve for absolute necrotic area required to identify OCT-TCFA was 0.86. The sensitivity, specificity, positive and negative predictive values of absolute necrotic area ≥7.3 mm2 for identifying OCT-TCFA were 77%, 88%, 68% and 92%, respectively.

Conclusions: Coronary lesions with greater iMap-IVUS absolute necrotic area were closely associated with OCT-TCFA.