Safety of the Deferral of Coronary Revascularization on the Basis of Instantaneous Wave-Free Ratio and Fractional Flow Reserve Measurements in Stable Coronary Artery Disease and Acute Coronary Syndromes

Objectives: The aim of this study was to investigate the clinical outcomes of patients deferredfrom coronary revascularizationon the basis of instantaneous wave-free ratio(iFR) or fractional flow reserve(FFR) measurements in stable angina pectoris (SAP) and acute coronary syndromes (ACS). Background: Assessment of coronary stenosis severity with pressure guidewires is recommended to determine the need for myocardial revascularization. Methods: The safety of deferralof coronary revascularizationin the pooled per-protocol population (n = 4,486) of the DEFINE-FLAIR (Functional Lesion Assessment of Intermediate Stenosis to Guide Revascularisation) and iFR-SWEDEHEART ( Instantaneous Wave-Free RatioVersus Fractional Flow Reservein Patients With Stable Angina Pectoris or Acute Coronary Syndrome) randomized clinical trials was investigated. Patients were stratified according to revascularizationdecision making on the basis of iFR or FFR and to clinical presentation (SAP or ACS). The primary endpoint was major adverse cardiac events ( MACE), defined as the composite of all-cause death, nonfatal myocardial infarction, or unplanned revascularizationat 1 year. Results: Coronary revascularizationwas deferredin 2,130 patients. Deferralwas performed in 1,117 patients (50%) in the iFR group and 1,013 patients (45%) in the FFR group (p < 0.01). At 1 year, the MACErate in the deferredpopulation was similar between the iFR and FFR groups (4.12% vs. 4.05%; fully adjusted hazard ratio: 1.13; 95% confidence interval: 0.72 to 1.79; p = 0.60). A clinical presentation with ACS was associated with a higher MACErate compared with SAP in deferredpatients (5.91% vs. 3.64% in ACS and SAP, respectively; fully adjusted hazard ratio: 0.61 in favor of SAP; 95% confidence interval: 0.38 to 0.99; p = 0.04). Conclusions: Overall, deferralof revascularizationis equally safe with both iFR and FFR, with a low MACErate of about 4%. Lesions were more frequently deferredwhen iFR was used to assess physiological significance. In deferredpatients presenting with ACS, the event rate was significantly increased compared with SAP at 1 year.