Purpose: We assessed the accuracy of coronary computed tomography angiography (CTA) in patients with an Agatston calcium score (ACS) of greater than 400 by comparing it with invasive coronary angiography (ICA), and we evaluated the predictive value of CTA for obstructive coronary heart disease (CHD) compared with traditional clinical risk assessment.
Methods: A total of 253 patients who had an ACS of greater than 400 were enrolled in this study. The degree of coronary stenosis was visually and quantitatively estimated by postprocessing imaging using 15-segment coronary models. All patients underwent ICA after a mean (SD) of 34 (24) days, and the degree of coronary stenosis was compared with the results of CTA.
Results: Computed tomography angiography accurately diagnosed significant stenosis in 204 (99.0%) of 206 patients and in 649 (83.5%) of 777 segments. When the patients were considered based on their ACS (group A, 400 < ACS ≤ 1000, vs group B, ACS > 1000), group B showed lower specificity (9.1% vs 41.7%) and poorer agreement (k = 0.149 vs 0.495) than for ICA. By segment-based analysis, the agreement between CTA and ICA was good (k = 0.729), and there was no significant difference between groups A (k = 0.728) and B (k = 0.727). Computed tomography angiography was the most powerful predictor (odds ratio = 52.645, P < 0.001), whereas the 10-year CHD risk and pretest probability were not significantly correlated with obstructive CHD.
Conclusions: Despite good overall diagnostic accuracy, coronary CTA in this group of patients was limited by low specificity. However, CTA was a better predictor of obstructive CHD compared with clinical predictors, and it avoided unnecessary ICA, even in patients with extensive coronary artery calcification.