Fractional flow reserve (FFR), defined as the ratio of maximal blood flow in a stenotic artery to maximum blood flow in the absence of stenosis, emerged as an important tool in clinical decision making and is recommended by current guidelines.1,2 FFR is calculated based on the assumption that there is a linear relationship between driving pressure and myocardial blood flow during maximal hyperemia. Therefore, since its introduction, the standard method for FFR measurement is achieving maximal hyperemia.