Resting Full-cycle Ratio (RFR)-Guided Revascularization

Myocardial ischemia is a key determinant of clinical prognosis in patients with coronary artery disease. In this regard, functional assessment of intermediate coronary stenoses with transtenotic pressure ratios provides a more accurate measure of stenosis-derived myocardial ischemia in comparison to conventional coronary angiography (3-5). One of the major clinical benefit of fractional flow reserve (FFR) is that, by acting as a gatekeeper, non-ischemia-causing lesions suitable for optimal medical treatment can be accurately identified, avoiding unnecessary coronary stenting. However, despite being support with the highest level of recommendation by the current guidelines for guiding clinical-decision making, adoption of FFR in the real world practice is still very low, mainly due to the need of hyperemic agents like adenosine that frequently cause patient discomfort, and time consumption. To overcome such limitations of pressure-wire derived index from the need of adenosine, other alternatives have been looking for over the last years. Instantaneous wave-free ratio (iFR), a resting trans-stenotic pressure index obtained as the ratio of distal coronary pressure to aortic pressure during the diastolic wave-free period, demonstrated a good diagnostic accuracy to define functional significance of coronary lesions without need of adenosine, using FFR as reference. Recently, two large, randomized trials demonstrated that iFR-guided coronary revascularization is clinically non-inferior to FFR-guided revascularization with respect to one-year risk of major adverse cardiac events. Accordingly, like FFR, iFR is now receiving the highest level of recommendations to guide clinical decision making in patients with stable intermediate coronary stenosis. A new adenosine-free index, the resting full-cycle ratio (RFR), has recently emerged. RFR is defined as the lowest ratio of intracoronary distal pressure to aortic pressure under resting condition, irrespective of systole or diastole, and has demonstrated equivalent diagnostic performance to iFR. RFR has an advantage over iFR, because it is not limited by sensitive land marking of components of the pressure waveform unlike iFR.

This novel physiologic index without the need of adenosine has the potential to increase the worldwide adoption of coronary physiology in guiding coronary revascularization in daily clinical practice. However, there is a paucity of important data regarding clinical outcomes of RFR-guided revascularization strategy. We hypothesize long-term clinical outcome of RFR-guided revascularization is non-inferior to that of FFR-guided revascularization, and it reduce the rate of PCI than FFR-guided revascularization. Therefore, we sought to investigate the long-term effectiveness and safety of RFR-based decision making in patients with one or more intermediate coronary stenosis, and to assess whether it is non-inferior to FFR-guided revascularization.