Association of Attenuated Plaques Detected by Intravascular Ultrasound With Plaque Calcification Assessed by Computed Tomography Angiography

Background: Coronary artery calcium (CAC) reflects the overall atherosclerotic burden. The CAC density is inversely associated with plaque vulnerability. Intravascular ultrasound (IVUS)-defined attenuated plaques represent unstable lesions, which are linked to adverse clinical outcomes. Meanwhile, the determination as to whether coronary computed tomography angiography (CCTA)-derived CAC metrics can serve as noninvasive markers of attenuated plaques remains uncertain. Methods: This retrospective study included coronary artery disease (CAD) patients who underwent both CCTA and IVUS between January 2023 and December 2024 at our medical center. CCTA was used to quantify plaque volume, density, and composition (lipid, fiber, and calcium), while IVUS was employed to characterize the plaques as attenuated and non-attenuated. Results: Among 94 patients with 150 coronary plaques, calcium volume showed a very strong correlation with total plaque volume (rs = 0.953, p < 0.0001). Meanwhile, attenuated plaques exhibited significantly lower calcium density (321.00 vs. 499.00 Hounsfield units (HU); p = 0.0004), calcium volume (55.20 vs. 168.10 mm3; p = 0.003), and calcium percentage (33.30% vs. 55.40%; p = 0.015) compared with the non-attenuated plaques. Multivariate logistic regression analysis identified lower CAC density as the only independent predictor of IVUS-confirmed attenuated plaques (odds ratio = 0.994, 95% confidence interval (CI): 0.990–0.997; p = 0.0002). The area under the receiver operating characteristic (AUROC) curve for CAC density in diagnosing attenuated plaques was 0.735 (95% CI: 0.603–0.868; p = 0.0004). At a cutoff of 461.50 HU, the sensitivity and specificity were 81.8% and 66.1%, respectively. Conclusion: CCTA-derived CAC volume reflects the atherosclerosis (AS) burden, while lower CAC density independently predicts IVUS-confirmed attenuated plaques. A higher CAC density was associated with plaque stability, suggesting that the CCTA-derived CAC density may serve as a noninvasive marker of plaque stability, aiding in the assessment of plaque vulnerability and risk stratification.