15 O‐water PET‐detected myocardial ischaemia and CT‐derived FFR: Predicting the functional significance of anatomical stenosis

Aims Coronary artery disease (CAD) is a major cause of morbidity and mortality worldwide. While coronary computed tomography angiography (CCTA) provides anatomical assessment of coronary stenoses, its ability to determine their functional significance is limited. Computed tomography‐derived fractional flow reserve (CT‐FFR) has emerged as a non‐invasive method for lesion‐specific ischaemia assessment. This study evaluated the diagnostic performance of CT‐FFR using 15 O‐water positron emission tomography (PET) myocardial perfusion imaging as the reference standard. Methods and Results We retrospectively reviewed 193 patients who underwent hybrid CCTA and 15 O‐water PET at Kuopio University Hospital between 2017 and 2022. Patients with low‐to‐moderate pretest probability of CAD in whom CAD could not be ruled out by CCTA were eligible. After exclusions, 165 patients were included. CT‐FFR values were calculated using a research prototype algorithm and compared with PET‐derived perfusion abnormalities. In the overall cohort, CT‐FFR showed moderate diagnostic performance, with area under the curve (AUC) values of 0.672–0.740. In a subgroup of 83 patients with high‐quality CCTA and stenosis >50%, diagnostic performance improved substantially (AUC 0.836). Using a CT‐FFR threshold of 0.80, sensitivity and specificity were 85% and 87%, respectively. Conclusion In an unselected clinical population referred for PET perfusion imaging after CCTA, CT‐FFR did not significantly improve diagnostic performance compared with CCTA alone. However, in patients with high‐quality CCTA and obstructive coronary stenoses, CT‐FFR demonstrated good accuracy for identifying functionally significant disease, supporting its role as a complementary non‐invasive diagnostic tool.