Impact of stenosis resistance and coronary flow capacity on fractional flow reserve and instantaneous wave-free ratio discordance: a combined analysis of DEFINE-FLOW and IDEAL

Background The pressure-derived parameters fractional flow reserve (FFR) and the emerging instantaneous wave-free ratio (iFR) are the most widely applied invasive coronary physiology indices to guide revascularisation. However, approximately 15–20% of intermediate stenoses show discordant FFR and iFR, and therapeutical consensus is lacking. Aims We sought to associate hyperaemic stenosis resistance index, coronary flow reserve (CFR) and coronary flow capacity (CFC) to FFR/iFR discordance. Methods We assessed pressure and flow measurements of 647 intermediate lesions (593 patients) of two multi-centre international studies. Results FFR and iFR were discordant in 15% of all lesions (97 out of 647). FFR+/iFR− lesions had similar hyperaemic average peak velocity (hAPV), CFR and CFC as FFR−/iFR− lesions, whereas FFR−/iFR+ lesions had similar hAPV, CFR and CFC as FFR+/iFR+ lesions ( p > 0.05 for all). FFR+/iFR− lesions were associated with lower baseline stenosis resistance, but not hyperaemic stenosis resistance, compared with FFR−/iFR+ lesions ( p < 0.001). Conclusions Discordance with FFR+/iFR− is characterised by maximal flow values, CFR, and CFC patterns similar to FFR−/iFR− concordance that justifies conservative therapy. Discordance with FFR−/iFR+ on the other hand, is characterised by low flow values, CFR, and CFC patterns similar to iFR+/FFR+ concordance that may benefit from percutaneous coronary intervention.