Physiologic mechanism of discordance between instantaneous wave-free ratio and fractional flow reserve: Insight from

Invasive physiologic indices, such as fractional flow reserve (FFR) or instantaneous wave-free ratio (iFR), are used in clinical practice. We sought to evaluate the physiological mechanism of discordance between iFR and FFR usingData from 113 patients, who underwent bothAmong the 113 patients, 39 (34.5%) showed concordant abnormal results in FFR and iFR measurement, and 17 (15.0%) showed discordant results between FFR and iFR (low FFR and high iFR). In comparison of coronary circulatory indices between discordant group and concordant abnormal group, both showed similar resting MBF (p=0.360), however, the discordant group showed higher hyperemic MBF and CFR, compared with the concordant abnormal group (p=0.003 and p0.001, respectively). Trans-stenosis resistance was lower in the discordant group, in both resting and hyperemic status (p0.001 for both). Although the discordant group showed higher resting microvascular resistance, these patients showed significantly higher reduction of microvascular resistance at hyperemia.Patients with low FFR despite high iFR showed significant differences in microvascular resistance, trans-stenosis resistance, absolute MBF, and CFR compared to those with concordant abnormal results between FFR and iFR.