BACKGROUND The invasive physiologic index such as fractional flow reserve (FFR) or instantaneous wave-free ratio (iFR) is used in clinical practice to identify ischemia-causing stenosis and to guide treatment strategy. We investigated clinical and angiographic characteristics of lesions with discrepancy between FFR and iFR.

METHODS From the 3V FFR-FRIENDS study, 975 vessels (393 patients) with available pre-intervention FFR and iFR were included in this study. The vessels were classified according to FFR and iFR into: concordant normal (Group 1 [n=724]: FFR>0.80 and iFR≥0.90); high FFR and low iFR (Group 2 [n=33]: FFR>0.80 and iFR<0.90); low FFR and high iFR (Group 3 [n=82]: FFR≤0.80 and iFR≥0.90); and concordant abnormal (Group 4 [n=136]: FFR≤0.80 and iFR<0.90).

RESULTS Angiographic stenosis severity assessed by percent diameter stenosis, minimum lumen diameter and lesion length was increased from Group 1 to Group 4 (all p<0.001). SYNTAX score increased and FFR decreased proportionally from Group 1 to Group 4 (all p<0.001). In multivariable GEE model, female, diabetes mellitus, smaller reference vessel diameter, and higher %DS were significantly associated with low iFR among high FFR groups (Group 2 discordance). Conversely, males, absence of diabetes mellitus and lower %DS were significantly associated with high iFR among low FFR groups (Group 3 discordance).

CONCLUSIONS Four groups classified according to FFR and iFR were different in clinical and angiographic characteristics, SYNTAX score, and predictors of discordance. The lesions with discordant FFR and iFR may need to be interpreted as a different clinical entity.