Prediction of coronary events by computed tomography-derived Murray law-based quantitative flow ratio

BACKGROUND: Coronary computed tomography angiography (CCTA)-derived Murray law-based quantitative flow ratio (CT-μFR) provides a non-invasive measure of vessel-level ischaemia but may not capture local haemodynamic abnormalities reflected by the longitudinal pressure gradient across the lesion (CT-μFR gradient). AIMS: We aimed to evaluate the association of CT-μFR and the CT-μFR gradient with 3-year vessel-level subsequent coronary events and to determine the incremental prognostic value of their combined assessment. METHODS: Our study included a total of 885 vessels from 312 patients who underwent invasive coronary angiography for acute coronary syndrome (ACS) or stable angina and had prior CCTA performed 6 months to 3 years earlier. CT-μFR and the CT-μFR gradient were assessed by an independent core laboratory blinded to the clinical data. The primary outcome was 3-year subsequent coronary events (a composite of vessel-specific myocardial infarction or urgent revascularisation for ACS). The discrimination ability of predictive models was assessed using Harrell's C-index. RESULTS: Vessels with CT-μFR ≤0.80 or a CT-μFR gradient ≥0.004/mm had a higher risk of events than those with CT-μFR>0.80 (79.1% vs 20.4%, adjusted hazard ratio [HR] 6.87, 95% confidence interval [CI]: 5.26-8.96; p<0.001) or a CT-μFR gradient <0.004/mm (72.6% vs 27.4%, adjusted HR 4.08, 95% CI: 3.15-5.28; p<0.001), respectively. Among vessels with CT-μFR>0.80, a CT-μFR gradient ≥0.004/mm remained associated with increased risk (adjusted HR 2.59, 95% CI: 1.63-4.11; p<0.001). Adding the CT-μFR gradient to CT-μFR improved discrimination in the overall cohort (C-index 0.700 to 0.755; p<0.001) as well as the subgroup with CT-μFR>0.80 (C-index 0.575 to 0.655; p<0.001). CONCLUSIONS: Both CT-μFR and the CT-μFR gradient are independently associated with 3-year subsequent coronary events. Their combined assessment improves risk stratification beyond CT-μFR alone. (ClinicalTrials.gov: NCT04794868).