Clinical relevance and prognostic implications of contrast quantitative flow ratio in patients with coronary artery disease

Background: We sought to evaluate the diagnostic performance of contrast quantitative flow ratio (cQFR) in all-comer patients with coronary artery disease, and to compare the vessel-oriented composite outcomes (VOCO) according to cQFR values. Method: 599 vessels with 452 patients who underwent clinically indicated fractional flow reserve (FFR) and cQFR measurement were evaluated. The cQFR, derived from 3-dimensional quantitative coronary angiography combined with TIMI frame-counts was compared with FFR as a reference standard. The risk of VOCO at 2 years, a composite of cardiac death, target-vessel myocardial infarction, and ischemia-driven target lesion revascularization, was compared according to cQFR and FFR value. Results: cQFR strongly correlated with FFR (r=0.860, p<0.001) and showed diagnostic accuracy of 91.2% to predict FFR≤0.80. cQFR showed significantly higher c-index to predict FFR≤0.80 (0.953, 95%CI 0.937-0.969) than %DS, percent area stenosis, resting distal coronary pressure/aortic pressure, and fixed QFR (p<0.001). Diagnostic accuracy of cQFR was not different according to various subgroups including non-culprit vessel of acute coronary syndrome and diabetes mellitus. Vessels with low cQFR (≤0.80) showed a significantly higher risk of VOCO at 2-year compared to those with high cQFR (>0.80) (HR 4.650, 95%CI 1.254-17.240, p=0.022). Discriminatory ability of cQFR for VOCO was similar with that of FFR (0.672 vs. 0.643, p=0.147). Conclusion: cQFR showed excellent correlation and diagnostic accuracy with FFR in diverse clinical presentations or patient characteristics. Low cQFR was significantly associated with a higher risk of VOCO at 2 years compared with high cQFR and cQFR showed similar discriminatory ability for VOCO with FFR.