Diagnostic Performance of In-Procedure Angiography-Derived Quantitative Flow Reserve Compared to Pressure-Derived Fractional Flow Reserve: The FAVOR II Europe-Japan Study

Abstract

Background: Quantitative flow ratio (QFR) is a novel modality for physiological lesion assessment based on 3-dimensional vessel reconstructions and contrast flow velocity estimates. We evaluated the value of online QFR during routine invasive coronary angiography for procedural feasibility, diagnostic performance, and agreement with pressure-wire-derived fractional flow reserve (FFR) as a gold standard in an international multicenter study.

Methods and results: FAVOR II E-J (Functional Assessment by Various Flow Reconstructions II Europe-Japan) was a prospective, observational, investigator-initiated study. Patients with stable angina pectoris were enrolled in 11 international centers. FFR and online QFR computation were performed in all eligible lesions. An independent core lab performed 2-dimensional quantitative coronary angiography (2D-QCA) analysis of all lesions assessed with QFR and FFR. The primary comparison was sensitivity and specificity of QFR compared with 2D-QCA using FFR as a reference standard. A total of 329 patients were enrolled. Paired assessment of FFR, QFR, and 2D-QCA was available for 317 lesions. Mean FFR, QFR, and percent diameter stenosis were 0.83±0.09, 0.82±10, and 45±10%, respectively. FFR was ≤0.80 in 104 (33%) lesions. Sensitivity and specificity by QFR was significantly higher than by 2D-QCA (sensitivity, 86.5% (78.4-92.4) versus 44.2% (34.5-54.3); P<0.001; specificity, 86.9% (81.6-91.1) versus 76.5% (70.3-82.0); P=0.002). Area under the receiver curve was significantly higher for QFR compared with 2D-QCA (area under the receiver curve, 0.92 [0.89-0.96] versus 0.64 [0.57-0.70]; P<0.001). Median time to QFR was significantly lower than median time to FFR (time to QFR, 5.0 minutes [interquartile range, -6.1] versus time to FFR, 7.0 minutes [interquartile range, 5.0-10.0]; P<0.001).

Conclusions: Online computation of QFR in the catheterization laboratory is clinically feasible and is superior to angiographic assessment for evaluation of intermediary coronary artery stenosis using FFR as a reference standard.

Clinical trial registration: URL: https://www.clinicaltrials.gov. Unique identifier: NCT02959814.

Keywords: fractional flow reserve; quantitative coronary angiography.

Figure 1

Study enrollment flow chart. FFR indicates fractional flow reserve; N, number of patients; QCA, quantitative coronary angiography; QFR, quantitative flow ratio; RCA, right coronary artery.

Figure 2

Sensitivity and specificity for QFR and 2D‐QCA with FFR as reference. QFR was superior to 2D‐QCA on sensitivity and specificity with FFR as reference standard. Diagnostic cutoffs: ≤0.80 for FFR and QFR; ≥50% DS for 2D‐QCA. 2D‐QCA indicates 2‐dimensional coronary angiography; QFR, quantitative flow ratio.

Figure 3

Per‐vessel level diagnostic performance. FFR≤0.80 was used as reference. 2D‐QCA indicates 2‐dimensional coronary angiography; AUC, area under the receiver operating curve; QFR, quantitative flow ratio.

Figure 4

Agreement between QFR and FFR. A good correlation (A) and agreement (B) of QFR and FFR was observed. Dashed lines in Bland–Altman plot illustrate mean difference ±2 SD. FFR indicates fractional flow reserve; QFR, quantitative flow ratio.

Figure 5

Comparison of time to FFR and time to QFR. FFR indicates fractional flow reserve; IQR, inter quartile range; m, minutes; QFR, quantitative flow ratio.