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.