Cardiovascular Medicine. 2016;19(03):67-71. Fournier S, Muller O. Fractional flow reserve (FFR) measurement has become the gold standard for assessing myocardial ischemia and has been recommended to decide to perform or not a myocardial revascularization in both American and European guidelines. Indeed, large clinical trials have demonstrated that an evaluation of stenoses guided by FFR reduced death, nonfatal myocardial infarction and repeat revascularization (MACE) when compared to an evaluation guided by angiography only and that a percutaneous coronary intervention (PCI) with an optimal medical treatment was superior to an optimal medical treatment alone to reduce MACE in presence of pathological FFR. To measure a FFR, the use pharmacological vasodilator (usually adenosine) is necessary. To avoid its administration, iFR recently emerged with the identification of a “wave-free period” of resistances similar in both magnitude and variability to those observed during FFR measurement. Nevertheless, iFR overall accuracy is only 80.4% and therefore iFR should not currently be recommended as an alternative to FFR.