Background: Coronary computed tomography angiography (CCTA) is applied in a growing number of clinical indications. This imaging modality is often regarded as a surrogate of invasive coronary angiography (ICA). In this paper we evaluate the applicability of CCTA alone in the assessment of the SYNTAX score.

Aim: To evaluate the feasibility of calculating the SYNTAX score (SXScore) using CCTA alone instead of ICA.

Methods: Ninety consecutive patients with multivessel or left main (LM) coronary artery disease diagnosed with ICA, in whom prior CCTA scan was available, were included in a post-hoc analysis. First, the SXScore was calculated twice in ten-week intervals by two experienced observers using ICA for each patient. Then the SXScore was calculated twice using CCTA following the same regimen for each patient. Weighted kappa statistic was used to assess the intra-modality and inter-modality reproducibility of the SXScore.

Results: Ninety patients, aged 63.8 ± 8.9 years, 60% male, 64.4% with two-vessel disease, and 35.6% with three-vessel or LM disease met the inclusion criteria. 287 lesions were identified by ICA and 280 by CCTA (p = 0.56). Median total SXScore was 11.5 (10.2–14.0) as calculated by ICA and 16.0 (14.3–19.4) by CCTA (p < 0.001), and the results were moderately correlated (R = 0.38). Inter-modality agreement between ICA and CCTA for SXScore tertiles was moderate (kappa = 0.40). The intra-modality reproducibility of ICA and CCTA for SXScore tertiles was 0.47 and 0.51, respectively.

Conclusions: Inter-modality agreement between CCTA and ICA for calculation of SXSscore is moderate but only slightly worse than intra-modality reproducibility for angiographic alone evaluation. Most of the observed variability can be assigned to the characteristic of the SXScore itself, not to the choice of imaging method. However, the application of CCTA for the assessment of SXScore should be used cautiously.