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Circ Cardiovasc Interv. 2014 Aug;7(4):492-502. doi: 10.1161/CIRCINTERVENTIONS.113.000926. Epub 2014 Jul 1.

Baseline instantaneous wave-free ratio as a pressure-only estimation of underlying coronary flow reserve: results of the JUSTIFY-CFR Study (Joined Coronary Pressure and Flow Analysis to Determine Diagnostic Characteristics of Basal and Hyperemic Indices of Functional Lesion Severity-Coronary Flow Reserve).

Author information

1
From the International Centre for Circulatory Health, National Heart and Lung Institute, Imperial College London and Imperial College Healthcare NHS Trust, London, United Kingdom (R.P., S.N., S.S., R.A.F., C.B., N.F., I.S.M., G.W.M., A.D.H., D.P.F., J.M., C.D.M., J.E.D.); Department of Cardiology, Academic Medical Centre, University of Amsterdam, Amsterdam, The Netherlands (T.P.v.d.H., M.A.v.L., J.J.P.); Cardiovascular Institute, Hospital Clínico San Carlos, Madrid, Spain (M.E.-P., J.E.); Amphia Hospital, Breda, The Netherlands (M.M.); and Cardiovascular Biomedical Research Unit, Royal Brompton Hospital, London, United Kingdom (C.D.M.).
2
From the International Centre for Circulatory Health, National Heart and Lung Institute, Imperial College London and Imperial College Healthcare NHS Trust, London, United Kingdom (R.P., S.N., S.S., R.A.F., C.B., N.F., I.S.M., G.W.M., A.D.H., D.P.F., J.M., C.D.M., J.E.D.); Department of Cardiology, Academic Medical Centre, University of Amsterdam, Amsterdam, The Netherlands (T.P.v.d.H., M.A.v.L., J.J.P.); Cardiovascular Institute, Hospital Clínico San Carlos, Madrid, Spain (M.E.-P., J.E.); Amphia Hospital, Breda, The Netherlands (M.M.); and Cardiovascular Biomedical Research Unit, Royal Brompton Hospital, London, United Kingdom (C.D.M.). justin.davies@imperial.ac.uk.

Abstract

BACKGROUND:

Coronary flow reserve has extensive validation as a prognostic marker in coronary disease. Although pressure-only fractional flow reserve (FFR) improves outcomes compared with angiography when guiding percutaneous coronary intervention, it disagrees with coronary flow reserve classification 30% of the time. We evaluated whether baseline instantaneous wave-free ratio (iFR) could provide an improved pressure-only estimation of underlying coronary flow reserve.

METHODS AND RESULTS:

Invasive pressure and flow velocity were measured in 216 stenoses from 186 patients with coronary disease. The diagnostic relationship between pressure-only indices (iFR and FFR) and coronary flow velocity reserve (CFVR) was compared using correlation coefficient and the area under the receiver operating characteristic curve. iFR showed a stronger correlation with underlying CFVR (iFR-CFVR, ρ=0.68 versus FFR-CFVR, ρ=0.50; P<0.001). iFR also agreed more closely with CFVR in stenosis classification (iFR area under the receiver operating characteristic curve, 0.82 versus FFR area under the receiver operating characteristic curve, 0.72; P<0.001, for a CFVR of 2). The closer relationship between iFR and CFVR was found for different CFVR cutoffs and was particularly marked in the 0.6 to 0.9 FFR range. Hyperemic FFR flow was similar to baseline iFR flow in functionally significant lesions (FFR ≤0.75; mean FFR flow, 25.8±13.7 cm/s versus mean iFR flow, 21.5±11.7 cm/s; P=0.13). FFR flow was higher than iFR flow in nonsignificant stenoses (FFR >0.75; mean FFR flow, 42.3±22.8 cm/s versus mean iFR flow, 26.1±15.5 cm/s; P<0.001).

CONCLUSIONS:

When compared with FFR, iFR shows stronger correlation and better agreement with CFVR. These results provide physiological evidence that iFR could potentially be used as a functional index of disease severity, independently from its agreement with FFR.

KEYWORDS:

coronary disease; fractional flow reserve, myocardial

[Indexed for MEDLINE]

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