Multicenter core laboratory comparison of the instantaneous wave-free ratio and resting Pd/Pa with fractional flow reserve: the RESOLVE study

J Am Coll Cardiol. 2014 Apr 8;63(13):1253-1261. doi: 10.1016/j.jacc.2013.09.060. Epub 2013 Nov 6.


Objectives: This study sought to examine the diagnostic accuracy of the instantaneous wave-free ratio (iFR) and resting distal coronary artery pressure/aortic pressure (Pd/Pa) with respect to hyperemic fractional flow reserve (FFR) in a core laboratory-based multicenter collaborative study.

Background: FFR is an index of the severity of coronary stenosis that has been clinically validated in 3 prospective randomized trials. iFR and Pd/Pa are nonhyperemic pressure-derived indices of the severity of stenosis with discordant reports regarding their accuracy with respect to FFR.

Methods: iFR, resting Pd/Pa, and FFR were measured in 1,768 patients from 15 clinical sites. An independent physiology core laboratory performed blinded off-line analysis of all raw data. The primary objectives were to determine specific iFR and Pd/Pa thresholds with ≥90% accuracy in predicting ischemic versus nonischemic FFR (on the basis of an FFR cut point of 0.80) and the proportion of patients falling beyond those thresholds.

Results: Of 1,974 submitted lesions, 381 (19.3%) were excluded because of suboptimal acquisition, leaving 1,593 for final analysis. On receiver-operating characteristic analysis, the optimal iFR cut point for FFR ≤0.80 was 0.90 (C statistic: 0.81 [95% confidence interval: 0.79 to 0.83]; overall accuracy: 80.4%) and for Pd/Pa was 0.92 (C statistic: 0.82 [95% confidence interval: 0.80 to 0.84]; overall accuracy: 81.5%), with no significant difference between these resting measures. iFR and Pd/Pa had ≥90% accuracy to predict a positive or negative FFR in 64.9% (62.6% to 67.3%) and 48.3% (45.6% to 50.5%) of lesions, respectively.

Conclusions: This comprehensive core laboratory analysis comparing iFR and Pd/Pa with FFR demonstrated an overall accuracy of ~80% for both nonhyperemic indices, which can be improved to ≥90% in a subset of lesions. Clinical outcome studies are required to determine whether the use of iFR or Pd/Pa might obviate the need for hyperemia in selected patients.

Keywords: coronary physiology; fractional flow reserve; myocardial ischemia.

Publication types

  • Clinical Trial
  • Comparative Study
  • Multicenter Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Blood Pressure
  • Cardiac Catheterization / methods*
  • Coronary Angiography
  • Coronary Circulation / physiology*
  • Coronary Stenosis / diagnosis*
  • Coronary Stenosis / physiopathology
  • Coronary Vessels / physiopathology*
  • Female
  • Follow-Up Studies
  • Fractional Flow Reserve, Myocardial / physiology*
  • Humans
  • Male
  • Middle Aged
  • Predictive Value of Tests
  • ROC Curve
  • Rest / physiology*
  • Retrospective Studies
  • Severity of Illness Index