Instantaneous wave-free ratio and fractional flow reserve in clinical practice

Objectives To compare fractional flow reserve (FFR) and instantaneous wave-free ratio (iFR) measurements in an all-comer patient population with moderate coronary artery stenoses. Background Visual assessment of the severity of coronary artery stenoses is often discordant in moderate lesions. FFR allows reliable functional severity assessment in these cases but requires adenosine-induced hyperaemia with associated additional time, costs and side effects. The iFR is a hyperaemia-independent index. Methods and results Between November 2015 and February 2017, 356 consecutive patients were included in whom 515 coronary stenoses were measured using both iFR and FFR. Mean iFR and FFR were 0.90 +/- 0.09 and 0.86 +/- 0.08, respectively. iFR correlated well with FFR [r=0.75; p<0.001]. Receiver operating characteristic analysis identified an area under the curve of 0.92. An iFR-only strategy with a treatment cut-off <= 0.89 revealed a diagnostic classification agreement with the FFR-only strategy in 420 lesions (82%) with a sensitivity of 87%, a specificity of 80%, a positive predictive value of 56% and a negative predictive value of 96%. Conclusions Real-time iFR measurements have good negative predictive value compared to FFR, but moderate diagnostic accuracy (82%). It exposes fewer patients to adenosine, reduces procedure time and costs. Further prospective trials are needed to evaluate specific clinical settings, cut-off values and endpoints.