Resting Full Cycle Ratio (RFR) and Instantaneous Wave-Free Ratio (iFR): Simultaneous Measurements for Assessment of Coronary Stenosis

摘要

In the absence of evidence of ischaemia, invasive functional assessment of intermediate-grade coronary stenosis is recommended [1]. Two large-scale randomized trials showed comparable outcomes between revascularization guided by the hyperaemic fractional flow reserve (FFR) and the resting diastolic instantaneous wave-free ratio (iFR), providing clinical evidence for the use of resting pressure-derived indices in coronary stenosis severity evaluation [2]. Furthermore, a recent study showed elegantly that a number of other diastolic resting indices were identical to iFR, both numerically and with respect to their agreement with FFR, suggesting a class effect among non-hyperaemic indices [3]. The resting full-cycle ratio (RFR) is a novel hyperaemia-free resting index of coronary artery severity [4]. It is calculated as the absolute lowest distal coronary pressure (Pd) to aortic pressure (Pa) ratio (Pd/Pa) during the whole cardiac cycle irrespective of systole or diastole. It was recently validated against instantaneous wave-free ratio (iFR) in a retrospective analysis of 651 waveforms in which iFR was measured using a proprietary Philips/Volcano wire. RFR was found to be diagnos-tically equivalent to iFR [4].