title: Diagnostic classification of the instantaneous wave-free ratio is equivalent to fractional flow reserve and is not improved with adenosine administration. Results of CLARIFY (Classification Accuracy of Pressure-Only Ratios Against Indices Using Flow Study).
abstract: OBJECTIVE
  This study sought to determine if adenosine administration is required for the pressure-only assessment of coronary stenoses.
  
  
  BACKGROUND
  The instantaneous wave-free ratio (iFR) is a vasodilator-free pressure-only measure of the hemodynamic severity of a coronary stenosis comparable to fractional flow reserve (FFR) in diagnostic categorization. In this study, we used hyperemic stenosis resistance (HSR), a combined pressure-and-flow index, as an arbiter to determine when iFR and FFR disagree which index is most representative of the hemodynamic significance of the stenosis. We then test whether administering adenosine significantly improves diagnostic performance of iFR.
  
  
  METHODS
  In 51 vessels, intracoronary pressure and flow velocity was measured distal to the stenosis at rest and during adenosine-mediated hyperemia. The iFR (at rest and during adenosine administration [iFRa]), FFR, HSR, baseline, and hyperemic microvascular resistance were calculated using automated algorithms.
  
  
  RESULTS
  When iFR and FFR disagreed (4 cases, or 7.7% of the study population), HSR agreed with iFR in 50% of cases and with FFR in 50% of cases. Differences in magnitude of microvascular resistance did not influence diagnostic categorization; iFR, iFRa, and FFR had equally good diagnostic agreement with HSR (receiver-operating characteristic area under the curve 0.93 iFR vs. 0.94 iFRa and 0.96 FFR, p = 0.48).
  
  
  CONCLUSIONS
  iFR and FFR had equivalent agreement with classification of coronary stenosis severity by HSR. Further reduction in resistance by the administration of adenosine did not improve diagnostic categorization, indicating that iFR can be used as an adenosine-free alternative to FFR.
authors.affiliation: International Centre for Circulatory Health, National Heart and Lung Institute, London, United Kingdom. sayan.sen@imperial.ac.uk
authors.forename: Sayan
authors.initials: S
authors.lastname: Sen
authors.forename: Kaleab N
authors.initials: KN
authors.lastname: Asrress
authors.forename: Sukhjinder
authors.initials: S
authors.lastname: Nijjer
authors.forename: Ricardo
authors.initials: R
authors.lastname: Petraco
authors.forename: Iqbal S
authors.initials: IS
authors.lastname: Malik
authors.forename: Rodney A
authors.initials: RA
authors.lastname: Foale
authors.forename: Ghada W
authors.initials: GW
authors.lastname: Mikhail
authors.forename: Nicolas
authors.initials: N
authors.lastname: Foin
authors.forename: Christopher
authors.initials: C
authors.lastname: Broyd
authors.forename: Nearchos
authors.initials: N
authors.lastname: Hadjiloizou
authors.forename: Amarjit
authors.initials: A
authors.lastname: Sethi
authors.forename: Mahmud
authors.initials: M
authors.lastname: Al-Bustami
authors.forename: David
authors.initials: D
authors.lastname: Hackett
authors.forename: Masood A
authors.initials: MA
authors.lastname: Khan
authors.forename: Muhammed Z
authors.initials: MZ
authors.lastname: Khawaja
authors.forename: Christopher S
authors.initials: CS
authors.lastname: Baker
authors.forename: Michael
authors.initials: M
authors.lastname: Bellamy
authors.forename: Kim H
authors.initials: KH
authors.lastname: Parker
authors.forename: Alun D
authors.initials: AD
authors.lastname: Hughes
authors.forename: Darrel P
authors.initials: DP
authors.lastname: Francis
authors.forename: Jamil
authors.initials: J
authors.lastname: Mayet
authors.forename: Carlo
authors.initials: C
authors.lastname: Di Mario
authors.forename: Javier
authors.initials: J
authors.lastname: Escaned
authors.forename: Simon
authors.initials: S
authors.lastname: Redwood
authors.forename: Justin E
authors.initials: JE
authors.lastname: Davies
mesh_terms: D000241:Adenosine / Q000008:administration & dosage*; D000368:Aged; D001783:Blood Flow Velocity / Q000502:physiology*; D003326:Coronary Circulation / Q000502:physiology; D023921:Coronary Stenosis / Q000175:diagnosis* / Q000503:physiopathology; D005260:Female; D053805:Fractional Flow Reserve, Myocardial / Q000502:physiology*; D006439:Hemodynamics; D006801:Humans; D006940:Hyperemia / Q000503:physiopathology; D007262:Infusions, Intravenous; D008297:Male; D008833:Microcirculation / Q000502:physiology; D008875:Middle Aged; D009200:Myocardial Contraction / Q000502:physiology; D010496:Pericardium / Q000473:pathology; D012372:ROC Curve; D014655:Vascular Resistance / Q000502:physiology; D014665:Vasodilator Agents / Q000008:administration & dosage*
chemical_list: D014665:Vasodilator Agents; D000241:Adenosine