Seasonal patterns in diagnosis of coronary artery disease by CT-angiography—experience from a large real-world cohort

INTRODUCTION: The seasonal influence on acute coronary syndromes is well established with higher incidence and worse outcomes in winter. Data on the impact of seasonal changes on the diagnosis of non-acute coronary artery disease (CAD) are limited. The aim of this study was to evaluate the influence of seasons on the diagnosis of CAD by coronary CT-angiography (CCTA). METHODS: Data from a CCTA practice were retrospectively analyzed (2020-2025). The following parameters were compared for each season: any CAD defined as the presence of atherosclerotic plaques and obstructive CAD defined as a stenosis ≥ 50% in CCTA, initiation of new medical therapy, and initiation of invasive coronary angiography (ICA) based on CCTA. RESULTS: In 10,023 CCTA cases, any CAD was diagnosed in 61.5% and obstructive CAD in 33.4% of patients. For obstructive CAD, the proportion varied only slightly across seasons, with rates of 35.1%, 34.1%, 31.4%, and 32.6% from spring to winter, respectively. Although the chi-square test indicated a nominal difference across seasons (p = 0.033), this was not confirmed in the regression analysis. Seasonal differences were observed in ICA initiation (spring to winter, 10.6%, 9.7%, 8.5%, 7.9%, p = 0.004), which was more likely during spring (OR 1.38 CI 95% 1.14-1.67, p < 0.001; reference, winter). CONCLUSION: In this large retrospective real-world cohort, the first-time diagnosis of obstructive CAD by CCTA showed only small seasonal differences. ICA was initiated modestly more often in spring than in winter. These findings should be considered hypothesis-generating and may reflect clinical, organizational, or referral-related factors rather than a direct seasonal effect.