Vessel fractional flow reserve (vFFR) is a novel angiography-derived index for the assessment of myocardial ischemia without the need for pressure wires and hyperemic agents. vFFR has demonstrated very good diagnostic performance compared with the hyperemic index fractional flow reserve (FFR). The aim of this study was to compare vFFR to the non-hyperemic pressure ratio resting full-cycle ratio (RFR).
Methods:
This was a retrospective, observational, single-center study of an all-comer cohort undergoing RFR assessment. Invasive coronary angiography was obtained without a dedicated vFFR acquisition protocol, and vFFR calculation was attempted in all vessels interrogated by RFR (1483 lesions of 1030 patients) using CAAS Workstation (Pie Medical Imaging, Maastricht, the Netherlands).
Results:
vFFR could be analyzed in 996 lesions from 712 patients. Median diameter stenosis was 37% (interquartile range (IQR): 29.5-44.0 %), vFFR 0.86 (IQR: 0.81-0.91) and RFR 0.94 (IQR: (0.90-0.97). The correlation between vFFR and RFR was strong (r=0.71, 95% confidence interval (CI): 0.67–0.75, p < 0.001) (Figure 1a) with good diagnostic agreement between both methods (Figure 1b). Using RFR ≤0.89 as reference, the sensitivity, specificity, positive predictive value, negative predictive value, and overall diagnostic accuracy for vFFR were 77%, 94%, 81%, and 93% and 90%. vFFR yielded a high area under the curve (AUC) of 0.92 (95% CI: 0.90-0.95) (Figure 3). The good diagnostic performance of vFFR was confirmed in several clinical subsets including females, patients with diabetes and aortic valve stenosis.
Conclusion:
vFFR has a high diagnostic performance taking RFR as the reference standard for evaluating the functional significance of coronary stenoses.
Figure 1. Correlation of vessel fractional flow reserve with invasive resting full-cycle ratio
Figure 2: Bland-Altman plot
There was a very strong correlation between vFFR and RFR (Figure 1) yield correlations and agreement between RFR and vFFR. The Bland-Altman plots (Figure 2) show the mean difference, which is represented with the 95% limits of agreement.
RFR. Resting full-cylce ratio, vFFR, vessel fractional flow reserve
Figure 3: Receiver operating characteristics curve
Receiver operating characteristics curve analysis for the diagnostic accuracy of vFFR in predicting RFR ≤0.89.
AUC, area under receiver operating characteristic curve
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