Background: Fractional flow reserve (FFR), as a functional measurement of coronary stenosis, is recommended for guiding revascularization in intermediate coronary lesions. However, it still remains underutilized for potential reasons including time consumption, costs, or contraindications associated with adenosine administration. Here we performed this meta-analysis to assess the diagnostic performance of two adenosine-free indices, instantaneous wave free-ratio (iFR), and quantitative flow ratio (QFR) in evaluating coronary stenosis severity with FFR as the reference standard.
Methods: PubMed, Embase, and Cochrane Central Register of Controlled Trials (CENTRAL) were searched to include relevant studies with the diagnostic accuracy of iFR or QFR referenced to FFR. A bivariate model was applied to pool diagnostic parameters. We used Cochran's Q test and I2 index to assess heterogeneity and identify the potential source of heterogeneity by meta-regression.
Results: A total of 8213 lesions from 28 studies (19 for iFR and 9 for QFR) were included in this meta-analysis. The pooled sensitivity and specificity were 0.79 (95% CI, 0.75 to 0.83) and 0.85 (95% CI, 0.82 to 0.87) for iFR and 0.90 (95% CI, 0.84 to 0.93) and 0.88 (95% CI, 0.86 to 0.90) for QFR, respectively. Significantly higher sensitivity and specificity were observed in the bivariate analysis for QFR than for iFR (P < 0.001 for both). The area under summary receiver-operating curve of iFR and QFR was 0.89 (95% CI, 0.86 to 0.92) and 0.92 (95% CI, 0.89 to 0.94).
Conclusion: Evidence suggests that both of the two indices have good performance in detecting functional ischemia of coronary arteries and QFR might be a promising method without requiring the pressure wire. Further application of QFR may potentially provide important information to clinicians in the assessment of coronary lesions.