Key result
An FFR threshold of 0.75 showed superior diagnostic performance (AUC 0.91) compared to an iFR threshold of 0.86 (AUC 0.79) and Pd/Pa (AUC 0.77) against an invasive reference standard (P=0.002).
Why the study?
Upward creep of FFR and iFR revascularization thresholds may increase revascularization despite questioning of its benefits in stable coronary disease.
Do optimal thresholds for FFR (0.75) and iFR (0.86) provide better diagnostic accuracy than contemporary thresholds (0.80 and 0.89) in patients with stable ischemic heart disease?
Observational (n=75)
Do optimal thresholds for FFR (0.75) and iFR (0.86) provide better diagnostic accuracy than contemporary thresholds (0.80 and 0.89) in patients with stable ischemic heart disease?
Effect estimate: AUC 0.91 vs 0.79
Absolute Event Rate: 84% vs 76%
p-value: p=0.002
Contemporary FFR and iFR thresholds provide suboptimal diagnostic accuracy compared to original derivation thresholds (FFR 0.75, iFR 0.86), suggesting more rigorous thresholds may better identify patients with significant ischemia.
FFR 0.75 may favor physiologic assessment accuracy; leaves open optimal thresholds and outcome impact versus iFR.
BACKGROUND: There has been a gradual upward creep of revascularization thresholds for both fractional flow reserve (FFR) and instantaneous wave-free ratio (iFR), before the clinical outcome trials for both indices. The increase in revascularization that has potentially resulted is at odds with increasing evidence questioning the benefits of revascularizing stable coronary disease. Using an independent invasive reference standard, this study primarily aimed to define optimal thresholds for FFR and iFR and also aimed to compare the performance of iFR, FFR, and resting distal coronary pressure (Pd)/central aortic pressure (Pa). METHODS AND RESULTS: Pd and Pa were measured in 75 patients undergoing coronary angiography±percutaneous coronary intervention with resting Pd/Pa, iFR, and FFR calculated. Doppler average peak flow velocity was simultaneously measured and hyperemic stenosis resistance calculated as hyperemic stenosis resistance=Pa-Pd/average peak flow velocity (using hyperemic stenosis resistance >0.80 mm Hg/cm per second as invasive reference standard). An FFR threshold of 0.75 had an optimum diagnostic accuracy (84%), whereas for iFR this was 0.86 (76%). At these thresholds, the discordance in classification between indices was 11%. The accuracy of contemporary thresholds (FFR, 0.80; iFR, 0.89) was significantly lower (78.7% and 65.3%, respectively) with a 25% rate of discordance. The optimal threshold for Pd/Pa was 0.88 (77.3% accuracy). When comparing indices at optimal thresholds, FFR showed the best diagnostic performance (area under the curve, 0.91 FFR versus 0.79 iFR and 0.77 Pd/Pa, P=0.002). CONCLUSIONS: Contemporary thresholds provide suboptimal diagnostic accuracy compared with an FFR threshold of 0.75 and iFR threshold of 0.86 (cutoffs in derivation studies). Whether more rigorous thresholds would result in selecting populations gaining greater symptom and prognostic benefit needs assessing in future trials of physiology-guided revascularization.
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Modi et al. (2018) conducted an observational in Coronary artery disease (n=75). Fractional flow reserve (FFR) and instantaneous wave-free ratio (iFR) vs. Hyperemic stenosis resistance was evaluated on Diagnostic accuracy (AUC 0.91 vs 0.79, p=0.002). An FFR threshold of 0.75 showed superior diagnostic performance (AUC 0.91) compared to an iFR threshold of 0.86 (AUC 0.79) and Pd/Pa (AUC 0.77) against an invasive reference standard (P=0.002).
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