Diagnostic Performance of Resting Full-Cycle Ratio Compared with Fractional Flow Reserve in Intermediate Coronary Stenosis

초록

BACKGROUND Resting full-cycle ratio (RFR) is a non-hyperemic index that may simplify physiologic assessment compared with adenosine-requiring fractional flow reserve (FFR). Evidence validating RFR against FFR in pre-percutaneous coronary intervention (PCI) decision-making remains limited. This prospective study evaluated the quantitative relationship and diagnostic agreement between RFR and FFR in intermediate coronary stenosis. METHODS In a single-center prospective cohort, 300 patients with angiographic 50–90% stenosis underwent pre-PCI invasive physiologic assessment with simultaneous RFR and FFR. Lesions with paired measurements (n=390) formed the analysis set. The primary endpoint was the correlation and agreement between RFR and FFR using Pearson correlation, linear regression, and Bland-Altman analysis. Secondary endpoints included threshold-based agreement using ischemic cutoffs (FFR ≤0.80, RFR ≤0.89), Cohen’s κ, and ROC performance for predicting FFR-defined ischemia. Safety outcomes included 30-day mortality and periprocedural complications. RESULTS RFR and FFR showed strong correlation (r=0.829) with a regression slope of 0.936 and intercept of 0.117. Bland-Altman analysis demonstrated a mean difference of +0.064, indicating a consistent positive bias of RFR relative to FFR. Threshold-based overall agreement was 85.1% with substantial concordance (κ=0.688). RFR predicted FFR ≤0.80 with excellent discrimination (AUC=0.931). In the borderline FFR range (0.77-0.83), agreement declined to 71.7%, with increased under-diagnosis (15.2%) and over-diagnosis (13.0%). Safety outcomes were favorable: 30-day mortality was 0%, and major periprocedural complications were rare (0.7%). CONCLUSION RFR demonstrates strong correlation, substantial diagnostic agreement, and high predictive performance relative to FFR in intermediate coronary stenosis. These findings support the clinical utility of RFR as a practical physiologic index in routine prePCI assessment.