Incremental Prognostic Value of Coronary Computed Tomography Angiography: High-Risk Plaque Characteristics in Asymptomatic Patients

Aim: Coronary computed tomography angiography (CCTA) findings of positive remodeling (index > 1.1) and low-attenuation plaque (< 30 Hounsfield units) are recognized as CT-verified high-risk plaque (CT-HRP). Therefore, we investigated the incremental prognostic value of evaluation of plaque characteristics using CCTA in asymptomatic patients. Methods: Overall, 495 consecutive patients without any known coronary artery disease who underwent CCTA were included in this study. Patients who underwent revascularization within 30 days of CCTA or had scans with poor image quality were excluded. Clinical follow-up data (716.5 ± 262.6 days) were available for 339 patients, who were analyzed for the current study. Framingham risk score (FRS), coronary artery calcium score (CACS), and CT-HRP were investigated as predictors of cardiac events by multivariable analysis using Cox proportional hazard model. Improvement of predictive accuracy by including CT findings was evaluated from reclassification [net reclassification indices (NRI) and integrated discrimination improvement (IDI)] standpoints. Results: During the follow-up period, 9 cardiac events (cardiac death: 0, nonfatal myocardial infarction: 2, hospitalization for unstable or progressive angina: 7) occurred. Multivariate Cox proportional hazard analysis demonstrated that CACS (HR, 13.23; 95% CI, 1.62–107.78, p < 0.0164) and CT-HRP (HR, 11.27; 95% CI, 1.24–102.12, p < 0.0321) were the independent predictors of cardiac events. NRI was 0.9556 (p < 0.0007) and IDI was 0.2582 (p < 0.0203), and the diagnostic performance improved by CT-HRP added to the combination of CACS and FRS. Conclusion: Although the cardiac event rate was low, the evaluation of CCTA plaque characteristics may provide incremental prognostic value to CACS in asymptomatic patients.