Department of Clinical Medicine

OBJECTIVES: To assess the diagnostic performance of quantitative flow ratio (QFR) for diagnosis of hemodynamically-significant coronary stenosis defined by fractional flow reserve (FFR) ≤0.80.

BACKGROUND: QFR is a novel angiography-based method for deriving FFR without pressure wire or induction of hyperemia. The accuracy of QFR when assessed online in the catheterization laboratory has not been adequately examined to date.

METHODS: This prospective, multicenter trial enrolled patients who had at least one lesion with diameter stenosis of 30-90% and reference diameter ≥ 2mm by visual estimation. QFR, quantitative coronary angiography (QCA), and wire-based FFR were assessed online in blinded fashion during coronary angiography and re-analyzed offline at an independent core laboratory. The primary endpoint was that QFR would improve the diagnostic accuracy of coronary angiography such that the lower boundary of the 2-sided 95% confidence interval (CI) of this estimate exceeded 75%.

RESULTS: Between June and July 2017, 308 patients were consecutively enrolled at 5 centers. Online QFR and FFR results were both obtained in 328 of 332 interrogated vessels. Patient-level and vessel-level diagnostic accuracy of QFR were 92.4% (95% CI: 88.9%-95.1%) and 92.7% (95% CI: 89.3%-95.3%), that were both significantly higher than the prespecified target value (p <0.001). Sensitivity and specificity in identifying hemodynamically-significant stenosis were significantly higher for QFR than QCA (sensitivity: 94.6% versus 62.5%, difference: 32.0%, p <0.001; specificity: 91.7% versus 58.1%, difference: 36.1%, p <0.001). Positive predictive value, negative predictive value, positive likelihood ratio, and negative likelihood ratio for QFR was 85.5%, 97.1%, 11.4, and 0.06, respectively. Offline analysis also showed vessel-level QFR had a high diagnostic accuracy of 93.3% (95% CI: 90.0%, 95.7%).

CONCLUSIONS: The study met its prespecified primary performance goal for the level of diagnostic accuracy of QFR in identifying hemodynamically-significant coronary stenosis.