Fat attenuation index and plaque characteristics on coronary computed tomography angiography correlation with high-risk plaques identified by optical coherence tomography

Background Coronary vulnerable plaques are the primary pathological substrate of acute coronary syndrome (ACS). Coronary computed tomography angiography (CCTA) facilitates non-invasive evaluation of plaque morphology and perivascular inflammation through the fat attenuation index (FAI). However, the systematic correlation between these CCTA-derived parameters and high-risk plaque (HRP) characteristics defined by high-resolution intracoronary optical coherence tomography (OCT) remains unclear. Objectives This study aims to assess the correlation between CCTA-derived plaque characteristics, FAI, and OCT-defined HRP. Methods Patients with non-ST-segment elevation ACS (NSTE-ACS) who underwent CCTA within one month before OCT examination were consecutively enrolled. The final cohort included 165 patients (262 plaques). Plaque characteristics on CCTA, including low-attenuation plaque (LAP), positive remodeling (PR), napkin-ring sign (NRS), spotty calcification (SC), and the FAI were assessed. OCT served as the reference standard for identifying HRP features, such as thin-cap fibroatheroma (TCFAs) or plaque rupture. Univariable and multivariable logistic regression analyses were performed to determine independent predictors of OCT-defined HRP, with diagnostic performance examined through receiver operating characteristic (ROC) curve analysis. Results Compared to non-HRP lesions, OCT-defined HRP lesions demonstrated a markedly elevated prevalence of LAP (53.8% vs. 33.1%, P < 0.001), NRS (48.7% vs. 26.2%, P < 0.001), and SC (35.0% vs. 22.8%, P = 0.028) on CCTA. These lesions also showed greater total plaque volume, non-calcified plaque volume, fibrous plaque volume, and fibrofatty plaque volume (P < 0.05). The FAI was notably higher in HRP lesions (-70.8±0.7 vs. -74.9±0.6, P < 0.001). Multivariable analysis revealed LAP (OR = 2.068, 95%CI:1.215-3.519, P = 0.007), FAI (OR = 1.069, 95%CI:1.030-1.109, P < 0.001), and fibrous plaque volume (OR = 1.025, 95%CI:1.009-1.042, P = 0.002) as independent predictors of OCT-defined HRP. The combination of these three parameters yielded an area under the curve (AUC) of 0.705 (P < 0.001) for diagnosing OCT-HRP. In the TCFA with plaque rupture subgroup, LAP (OR = 6.628, 95%CI:2.067-21.255, P = 0.001), PR (OR = 2.897, 95%CI:1.011-8.302, P = 0.048), and FAI (OR = 1.091, 95%CI:1.012-1.177, P = 0.023) were independent predictors, and their combined use yielded an AUC of 0.842 (P < 0.001). Conclusions CCTA-derived plaque characteristics and FAI show significant associations with OCT-defined vulnerable plaques. The integrated use of these parameters enhances diagnostic accuracy for identifying OCT-HRP, particularly the very-high-risk phenotype of TCFA with plaque rupture. Multi-parametric CCTA assessment provides a robust imaging foundation for non-invasive risk stratification and precision management of individuals with coronary artery disease.