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Classification performance of instantaneous wave-free ratio (iFR) and fractional flow reserve in a clinical population of intermediate coronary stenoses: results of the ADVISE registry

Selected in EuroIntervention by S. Brugaletta

References

Authors

Petraco R, Escaned J, Sen S, Nijjer S, Asrress KN, Echavarria-Pinto M, Lockie T, Khawaja MZ, Cuevas C, Foin N, Broyd C, Foale RA, Hadjiloizou N, Malik IS, Mikhail GW, Sethi A, Kaprielian R, Baker CS, Lefroy D, Bellamy M, Al-Bustami M, Khan MA, Hughes AD, Francis DP, Mayet J, Di Mario C, Redwood S, Davies JE.

Reference

EuroIntervention. 2013 May 20;9(1):91-101

Published

May 2011

Link

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Aims

To evaluate the classification agreement between instantaneous wave-free ratio (iFR) and fractional flow reserve (FFR) in patients with angiographic intermediate coronary stenoses.

Methods and results

Three hundred and twelve patients (339 stenoses) with angiographically intermediate stenoses were included in this international clinical registry. The iFR was calculated using fully automated algorithms. The receiver operating characteristic (ROC) curve was used to identify the iFR optimal cut-point corresponding to FFR 0.8. The classification agreement of coronary stenoses as significant or non-significant was established between iFR and FFR and between repeated FFR measurements for each 0.05 quantile of FFR values, from 0.2 to 1. Close agreement was observed between iFR and FFR (area under ROC curve= 86%). The optimal iFR cut-off (for an FFR of 0.80) was 0.89. After adjustment for the intrinsic variability of FFR, the classification agreement (accuracy) between iFR and FFR was 94%. Amongst the stenoses classified as non-significant by iFR (>0.89) and as significant by FFR (≤0.8), 81% had associated FFR values located within the FFR “grey-zone” (0.75-0.8) and 41% within the 0.79-0.80 FFR range.

Conclusions

In a population of intermediate coronary stenoses, the classification agreement between iFR and FFR is excellent and similar to that of repeated FFR measurements in the same sample. Vasodilator-independent assessment of intermediate stenosis seems applicable and may foster adoption of coronary physiology in the catheterisation laboratory.

My Comment

What is known

Instantaneous wave-free ratio (iFR) is a recently proposed invasive pressure-derived index of coronary stenosis severity. It differs from fractional flow reserve (FFR) as it does not require the administration of vasodilators for its calculation. iFR is calculated from trans-stenotic pressure measurements as the ratio of distal to proximal coronary pressures during a specific wave-free period of the cardiac cycle, when microvascular resistance is intrinsically stable and minimised. The present study evaluated the level of agreement between iFR and FFR in a cohort of patients with intermediate coronary stenoses investigated with pressure guidewires as part of their clinical assessment.

Major findings

Three hundred and twelve patients (339 stenoses) with angiographically intermediate stenoses were included

  • Close agreement was observed between iFR and FFR (area under ROC curve= 86%).
  • The optimal iFR cut-off (for an FFR of 0.80) was 0.89
  • After adjustment for the intrinsic variability of FFR, the classification agreement (accuracy) between iFR and FFR was 94%
  • Amongst the stenoses classified as non-significant by iFR (>0.89) and as significant by FFR (≤0.8), 81% had associated FFR values located within the FFR “grey-zone” (0.75-0.8) and 41% within the 0.79-0.80 FFR range

My comments

The present registry, which is complementary to the ADVISE study, finds an excellent classification agreement between iFR and FFR in a registry population that is formed by coronary stenoses with predominantly intermediate physiological and angiographic severities. Of note is that in this clinical iFR registry, the optimal established cut-off value for iFR to identify stenoses with FFR of 0.80 was 0.89. This value was higher than the 0.83 optimal iFR cut-off observed in the ADVISE study but similar to the one observed in other studies comparing iFR and FFR in clinical populations. Therefore, the authors suggested that the iFR 0.89 cut-off may represent the value of iFR which can be considered the best iFR cut-off to identify 0.8 FFR stenoses in clinical practice. In this regard, the ADVISE-II study will likely add another important piece of information on iFR, opening its use in clinical practice with established threshold.

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