Characterization of quantitative flow ratio and fractional flow reserve discordance using doppler flow and clinical follow-up

The physiological mechanisms of quantitative flow ratio and fractional flow reserve disagreement are not fully understood. We aimed to characterize the coronary flow and resistance profile of intermediate stenosed epicardial coronary arteries with concordant and discordant FFR and QFR. Post-hoc analysis of the DEFINE-FLOW study. Anatomical and Doppler-derived physiological parameters were compared for lesions with FFR+QFR- (n = 18) vs. FFR+QFR+ (n = 43) and for FFR-QFR+ (n = 34) vs. FFR-QFR- (n = 139). The association of QFR results with the two-year rate of target vessel failure was assessed in the proportion of vessels (n = 195) that did not undergo revascularization. Coronary flow reserve was higher [2.3 (IQR: 2.1-2.7) vs. 1.9 (IQR: 1.5-2.4)], hyperemic microvascular resistance lower [1.72 (IQR: 1.48-2.31) vs. 2.26 (IQR: 1.79-2.87)] and anatomical lesion severity less severe [% diameter stenosis 45.5 (IQR: 41.5-52.5) vs. 58.5 (IQR: 53.1-64.0)] for FFR+QFR- lesions compared with FFR+QFR+ lesions. In comparison of FFR-QFR+ vs. FFR-QFR- lesions, lesion severity was more severe [% diameter stenosis 55.2 (IQR: 51.7-61.3) vs. 43.4 (IQR: 35.0-50.6)] while coronary flow reserve [2.2 (IQR: 1.9-2.9) vs. 2.2 (IQR: 1.9-2.6)] and hyperemic microvascular resistance [2.34 (IQR: 1.85-2.81) vs. 2.57 (IQR: 2.01-3.22)] did not differ. The agreement and diagnostic performance of FFR using hyperemic stenosis resistance (> 0.80) as reference standard was higher compared with QFR and coronary flow reserve. Disagreement between FFR and QFR is partly explained by physiological and anatomical factors. Clinical Trials Registration https://www.clinicaltrials.gov ; Unique identifier: NCT01813435.