Relationship between resting full‐cycle ratio and fractional flow reserve in assessments of coronary stenosis severity

AIM: Comparisons between the resting full-cycle ratio (RFR), a new physiological resting index, and fractional flow reserve (FFR) in terms of prognostic value are limited. We aimed to identify the prognostic value of concordance between RFR and FFR and to determine the stability of measured RFR. METHODS AND RESULTS: We measured FFR and RFR in 161 coronary arteries of 119 patients and classified the data using known cutoffs for FFR (≤0.80) and RFR (≤0.89) into groups; high FFR and high RFR (high FFR/low RFR) group, high FFR and low RFR (high FFR/low RFR) group, low FFR and high RFR (low FFR/high RFR) group, and low FFR and low RFR (low FFR/low RFR) group. The concordance rates in these groups were 42.2% (68/161), 4.4% (7/161), 14.3% (23/161), and 39.1% (63/161), respectively. The concordance between FFR and RFR was 81.4%. The prevalence of females was significantly higher, values for hemoglobin values were significantly lower, and average E/E' (an index of left ventricular (LV) diastolic function by echocardiography) was significantly higher in high FFR/low RFR group than in low FFR/high RFR group (p = .008, .050, and .028, respectively). CONCLUSIONS: The RFR and FFR values consistently agreed. Female, anemia, and LV diastolic dysfunction may be related to the difference of discordance between high FFR/low RFR and low FFR/high RFR.