Different trials have shown that fractional flow reserve (FFR) could successfully guide revascularization in patients undergoing percutaneous coronary intervention (PCI). It is conceivable that a similar revascularization guidance could be useful also for surgical revascularization i.e. coronary by-pass graft (CABG). Experience learns that grafts placed on vessels with hemodynamically non-significant stenosis often occlude due to competitive antegrade flow. Resting full-cycle Flow Ratio (RFR) is a measurement performed to evaluate the hemodynamic severity of coronary stenosis. Differently from FFR which is a measurement performed in maximal hyperemia, the RFR is a measurement that is performed in rest and therefore may predict better than FFR the baseline equilibriums that could lead to graft failure, while it has similar capacity to identify hemodynamically significant stenosis as FFR. It is unknown whether RFR guided CABG revascularization is superior as compared to angiography alone.