Computational quantitative flow ratio to assess functional severity of coronary artery stenosis

Background Computational quantitative flow ratio (QFR) based on 3-dimensional quantitative coronary angiography (3D QCA) analysis offers the opportunity to assess the significance of coronary artery disease (CAD) without using an invasive pressure wire or inducing hyperemia. This study aimed to evaluate the diagnostic performance of QFR compared to wire-based fractional flow reserve (FFR) and to validate the previously reported QFR cut-off value of >0.90 to safely rule out functionally significant CAD. Methods QFR was retrospectively derived from standard-care coronary angiograms. Correlation and agreement of fixed-flow QFR (fQFR) and contrast-flow QFR (cQFR) models with invasive wire-based FFR was calculated. Diagnostic performance of QFR was evaluated at different QFR cut-off values defining significant CAD (FFR ≤ 0.80). Results 101 vessels in 96 patients who underwent FFR were studied. Mean FFR was 0.87 ± 0.08 and 21 of 101 (21%) vessels had an FFR ≤ 0.80. Correlation of fQFR and cQFR with FFR was r = 0.71 (p < 0.001) and r = 0.70 (p < 0.001), respectively. Sensitivity and specificity were 57% and 93% for fQFR and 67% and 96% for cQFR at a QFR cut-off value >0.80 defining non-significant CAD, respectively. fQFR > 0.90 was present in 34 (34%) and cQFR > 0.90 in 39 (39%) vessels. For both QFR models, none of the vessels with QFR > 0.90 had an FFR ≤ 0.80. Conclusions QFR appears to be a safe and effective gatekeeper to wire-based FFR when applying a QFR threshold of >0.90 to rule out significant CAD. Further prospective research is required to establish QFR in the real-life setting of functional CAD assessment in the catheterization laboratory.