Impact of contrast material on calcium burden by coronary computed tomography angiography

Background: Coronary computed tomography angiography (CCTA) helps reveal complex coronary lesions and improves the success and complication rates of coronary interventions for the lesions. CCTA has also been used to quantify coronary plaque volumes, including calcified plaques. However, the precise evaluation of calcified lesions is deemed unsuitable due to blooming artifacts, and the use of contrast media also makes it difficult to differentiate between luminal contrast and calcified plaque. Methods: In this pilot study, 38 severely calcified coronary lesions in 21 patients who underwent CCTA were included. Both contrast and non-contrast scans were collected for subtraction using a forward-projected model-based iterative reconstruction. Calcium volume, maximum calcium thickness, length, maximum intensity, and arc of the calcified lesions were measured on both scan images. Results: Calcium volume (90.9 [70.5, 175.7] vs. 43.4 [25.5, 95.5] mm3, p < 0.01), maximum thickness (3.00 [2.73, 3.60] vs. 2.25 [1.80, 2.70] mm, p < 0.01), length (14.2 [12.2, 24.9] vs. 12.0 [10.5, 20.7] mm, p < 0.01), and maximum intensity (1759.5 [1675.0, 1829.3] vs. 1712.5 [1513.3, 1783.5] HU, p < 0.01) were significantly higher in the non-contrast scan, while these parameters were well correlated between both images. The agreement of calcium arc was fair to good (kappa = 0.67). In the Bland–Altman analysis, there were absolute differences in calcium volume, maximum calcium thickness, length, and maximum intensity, and a percentage difference was observed in calcium volume. Conclusions: Contrast media significantly impacted the quantification of calcified plaque. Thus, we should carefully evaluate calcified plaque using CCTA in complex coronary interventions because accurate assessment is crucial for predicting the need for atherectomy.