Predictive factors of discordance between the instantaneous wave-free ratio and fractional flow reserve

Objectives: To identify clinical, angiographic and hemodynamic predictors of discordance between instantaneous wave-free ratio (iFR) and fractional flow reserve (FFR). Background: The iFR was found to be non-inferior to the gold-standard FFR for guiding coronary revascularization, although it is discordant with FFR in 20% of cases. A better understanding of the causes of discordance may enhance application of these indices. Methods: Both FFR and iFR were measured in the prospective multicenter CONTRAST study. Clinical, angiographic and hemodynamic variables were compared between patients with concordant values of FFR and iFR (cutoff ≤0.80 and ≤0.89, respectively). Results: Out of the 587 patients included, in 466 patients (79.4%) FFR and iFR agreed: both negative, n = 244 (41.6%), or positive, n = 222 (37.8%). Compared with FFR, iFR was negative discordant (FFR+/iFR-) in 69 (11.8%) patients and positive discordant (FFR-/iFR+) in 52 (8.9%) patients. On multivariate regression, stenosis location (left main or proximal left anterior descending) (OR: 3.30[1.68;6.47]), more severe stenosis (OR: 1.77[1.35;2.30]), younger age (OR: 0.93[0.90;0.97]), and slower heart rate (OR: 0.59[0.42;0.75]) were predictors of a negative discordant iFR. Absence of a beta-blocker (OR: 0.41[0.22;0.78]), older age (OR: 1.04[1.00;1.07]), and less severe stenosis (OR: 0.69[0.53;0.89]) were predictors of a positive discordant iFR. Conclusions: During iFR acquisition, stenosis location, stenosis degree, heart rate, age and use of beta blockers influence concordance with FFR and should be taken into account when interpreting iFR.