Coronary Revascularization Guided With Fractional Flow Reserve or Instantaneous Wave-Free Ratio: A 5-Year Follow-Up of the DEFINE FLAIR Randomized Clinical Trial.

Importance: The differences between the use of fractional flow reserve (FFR) or instantaneous wave-free ratio (iFR) in the long term are unknown.

Objective: To compare long-term outcomes of iFR- and FFR-based strategies to guide revascularization.

Design, Setting, And Participants: The DEFINE-FLAIR multicenter study randomized patients with coronary artery disease to use either iFR or FFR as a pressure index to guide revascularization. Patients from 5 continents with coronary artery disease and angiographically intermediate severity stenoses who underwent hemodynamic interrogation with pressure wires were included. These data were analyzed from March, 13, 2014, through April, 27, 2021.

Main Outcome Measures: Five-year major adverse cardiac events (MACE) (a composite of all-cause death, nonfatal myocardial infarction, and unplanned revascularization), as well as the individual components of the combined end point.

Results: At 5 years of follow-up, no significant differences were found between the iFR (mean age [SD], 65.5 [10.8] years; 962 male [77.5%]) and FFR (mean age [SD], 65.2 [10.6] years; 929 male [74.3%]) groups in terms of MACE (21.1% vs 18.4%, respectively; hazard ratio [HR], 1.18; 95% CI, 0.99-1.42; P = .06). While all-cause death was higher among patients randomized to iFR, it was not driven by myocardial infarction (6.3% vs 6.2% in the FFR study arm; HR, 1.01; 95% CI, 0.74-1.38; P = .94) or unplanned revascularization (11.9% vs 12.2% in the FFR group; HR, 0.98; 95% CI, 0.78-1.23; P = .87). Furthermore, patients in whom revascularization was deferred on the basis of iFR or FFR had similar MACE in both study arms (17.9% in the iFR group vs 17.5% in the FFR group; HR, 1.03; 95% CI, 0.79-1.35; P = .80) with similar rates of the components of MACE, including all-cause death. On the contrary, in patients who underwent revascularization after physiologic interrogation, the incidence of MACE was higher in the iFR group (24.6%) compared with the FFR group (19.2%) (HR, 1.36; 95% CI, 1.07-1.72; P = .01).

Conclusions And Relevance: At 5-year follow up, an iFR based-strategy was not statistically different than an FFR strategy to guide revascularization in terms of MACE, nonfatal myocardial infarction, and unplanned revascularization.

Trial Registration: ClinicalTrials.gov Identifier: NCT02053038.