title: Comparison of instantaneous wave-free ratio (iFR) and fractional flow reserve (FFR)--first real world experience.
abstract: BACKGROUND
  The instantaneous wave-free ratio (iFR) is a new adenosine-independent index of coronary stenosis severity. Most published data have been based on off-line analyses of pressure recordings in a core laboratory. We prospectively compared real-time iFR and fractional flow reserve (FFR) measurements.
  
  
  RESULTS
  iFR and FFR were measured in 151 coronary stenoses in 108 patients. Repeated iFR measurements were technically simple, showed excellent agreement [rs=0.99; p<0.0001], and the mean difference between consecutive iFR values was 0.0035 (limits of agreement: -0.019, 0.026). Mean iFR showed a significant correlation with FFR [rs=0.81; p<0.0001]. Receiver-operating characteristic analysis identified an optimal iFR cut-off value of 0.896 for categorization based on an FFR cut-off value 0.8. We compared two different iFR-based diagnostic strategies (iFR-only and hybrid iFR-FFR) with standard FFR: The iFR-only strategy showed good classification agreement (83.4%) with standard FFR. Use of the hybrid iFR-FFR strategy, assessing lesions in an iFR-gray zone of 0.86-0.93 by FFR, improved classification accuracy to 94.7%, and diagnosis would have been established in 61% of patients without adenosine-induced hyperemia. Notably, both iFR and FFR values were significantly higher in the posterior coronary vessels.
  
  
  CONCLUSIONS
  Real-time iFR measurements are easily performed, have excellent diagnostic performance and confirm available off-line core laboratory data. The excellent agreement between repeated iFR measurements demonstrates the reliability of single measurements. Combining iFR with FFR in a hybrid strategy enhances diagnostic accuracy, exposing fewer patients to adenosine. Overall, iFR is a promising method, but still requires prospective clinical endpoint trial evaluation.
authors.affiliation: Klinikum Oldenburg, Klinik für Kardiologie, Oldenburg, Germany. Electronic address: t.haerle@gmx.de.
authors.forename: Tobias
authors.initials: T
authors.lastname: Härle
authors.affiliation: Gemeinschaftsklinikum Koblenz-Mayen, Medizinische Klinik II, Koblenz, Germany.
authors.forename: Waldemar
authors.initials: W
authors.lastname: Bojara
authors.affiliation: Klinikum Oldenburg, Klinik für Kardiologie, Oldenburg, Germany; University of Groningen, University Medical Center Groningen, Department of Cardiology, Groningen, The Netherlands.
authors.forename: Sven
authors.initials: S
authors.lastname: Meyer
authors.affiliation: Klinikum Oldenburg, Klinik für Kardiologie, Oldenburg, Germany.
authors.forename: Albrecht
authors.initials: A
authors.lastname: Elsässer
mesh_terms: D000368:Aged; D006328:Cardiac Catheterization; D017023:Coronary Angiography; D023921:Coronary Stenosis / Q000000981:diagnostic imaging / Q000503:physiopathology*; D003331:Coronary Vessels / Q000000981:diagnostic imaging / Q000503:physiopathology*; D005260:Female; D005500:Follow-Up Studies; D053805:Fractional Flow Reserve, Myocardial / Q000502:physiology*; D006801:Humans; D008297:Male; D011446:Prospective Studies; D012372:ROC Curve; D015203:Reproducibility of Results; D012720:Severity of Illness Index
keywords: Coronary stenosis; Hydrostatic pressure; Instantaneous wave-free ratio; Intermediate stenosis; Physiological assessment; Real-time