Evaluation of Coronary Artery Stenosis by Quantitative Flow Ratio during Invasive Coronary Angiography: The WIFI II Study (Wire-Free Functional Imaging II)

Jelmer Westra*, Shengxian Tu, Simon Winther, Louise Nissen, Mai Britt Vestergaard, Birgitte Krogsgaard Andersen, Emil Nielsen Holck, Camilla Fox Maule, Jane Kirk Johansen, Lene Nyhus Andreasen, Jo Krogsgaard Simonsen, Yimin Zhang, Steen Dalby Kristensen, Michael Maeng, Anne Kaltoft, Christian Juhl Terkelsen, Lars Romer Krusell, Lars Jakobsen, Johan H.C. Reiber, Jens Flensted LassenMorten Bøttcher, Hans Erik Bøtker, Evald Høj Christiansen, Niels Ramsing Holm

*Corresponding author for this work

Research output: Contribution to journalJournal articleResearchpeer-review


Background - Quantitative flow ratio (QFR) is a novel diagnostic modality for functional testing of coronary artery stenosis without the use of pressure wires and induction of hyperemia. QFR is based on computation of standard invasive coronary angiographic imaging. The purpose of WIFI II (Wire-Free Functional Imaging II) was to evaluate the feasibility and diagnostic performance of QFR in unselected consecutive patients. Methods and Results - WIFI II was a predefined substudy to the Dan-NICAD study (Danish Study of Non-Invasive Diagnostic Testing in Coronary Artery Disease), referring 362 consecutive patients with suspected coronary artery disease on coronary computed tomographic angiography for diagnostic invasive coronary angiography. Fractional flow reserve (FFR) was measured in all segments with 30% to 90% diameter stenosis. Blinded observers calculated QFR (Medis Medical Imaging bv, The Netherlands) for comparison with FFR. FFR was measured in 292 lesions from 191 patients. Ten (5%) and 9 patients (5%) were excluded because of FFR and angiographic core laboratory criteria, respectively. QFR was successfully computed in 240 out of 255 lesions (94%) with a mean diameter stenosis of 50±12%. Mean difference between FFR and QFR was 0.01±0.08. QFR correctly classified 83% of the lesions using FFR with cutoff at 0.80 as reference standard. The area under the receiver operating characteristic curve was 0.86 (95% confidence interval, 0.81-0.91) with a sensitivity, specificity, negative predictive value, and positive predictive value of 77%, 86%, 75%, and 87%, respectively. A QFR-FFR hybrid approach based on the present results enables wire-free and adenosine-free procedures in 68% of cases. Conclusions - Functional lesion evaluation by QFR assessment showed good agreement and diagnostic accuracy compared with FFR. Studies comparing clinical outcome after QFR- and FFR-based diagnostic strategies are required.

Original languageEnglish
Article number007107
JournalCirculation: Cardiovascular Imaging
Issue number3
Publication statusPublished - 1. Mar 2018
Externally publishedYes

Bibliographical note

Publisher Copyright:
© 2018 The Authors.


  • adenosine
  • angiography
  • coronary angiography
  • coronary artery disease
  • hyperemia
  • Severity of Illness Index
  • Predictive Value of Tests
  • Reproducibility of Results
  • Prospective Studies
  • Computed Tomography Angiography/methods
  • Coronary Stenosis/diagnosis
  • Imaging, Three-Dimensional/methods
  • Humans
  • Middle Aged
  • Male
  • Telemedicine/methods
  • Fractional Flow Reserve, Myocardial/physiology
  • Female
  • ROC Curve
  • Coronary Vessels/diagnostic imaging
  • Coronary Angiography/methods


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