Fractional flow reserve and pressure-bounded coronary flow reserve to predict outcomes in coronary artery disease.

AIMS: Fractional flow reserve (FFR) has proven to its prognostic and therapeutic value. However, the additive prognostic value of coronary flow reserve (CFR) remains unclear. This study sought to investigate the clinical utility of combined FFR and CFR measurements to predict outcomes. METHODS AND RESULTS: Using the prospective, multicentre Interventional Cardiology Research Incooperation Society-FFR registry, a total of 2088 lesions from 1837 patients were included in this substudy. Based on baseline and hyperaemic pressure gradients, we computed physiologic limits of CFR [the so called pressure-bounded (pb) CFR] and classified lesions as low (<2) or high (≥2). The primary endpoint was major adverse cardiac events (MACE, a composite of cardiac death, myocardial infarction, and revascularization) analysed on a per-patient basis. During a median follow-up of 1.9 years (inter-quartile range: 1.0-3.0 years), MACE occurred in 5.7% of patients with FFR ≤0.80 vs. 2.8% of patients with FFR >0.80 [adjusted hazard ratio (aHR): 2.15, 95% confidence interval (CI): 1.19-3.89; P = 0.011. In contrast, the incidence of MACE did not differ between patients with pb-CFR < 2 vs. pb-CFR ≥ 2 (4.2% vs. 4.2%; aHR: 0.98, CI: 0.60 to 1.58; P = 0.92). Incorporation of FFR significantly improved model prediction of MACE (global χ2 38.8-48.1, P = 0.002). However, pb-CFR demonstrated no incremental utility to classify outcomes (global χ2 48.1-48.2, P > 0.99). CONCLUSIONS: In this large, prospective registry of over 2000 coronary lesions, FFR was strongly associated with clinical outcomes. In contrast, a significant association between pb-CFR and clinical events could not be determined and adding knowledge of pb-CFR did not improve prognostication over FFR alone.