The fractional flow reserve gray zone has never been so narrow

Fractional flow reserve (FFR) is the gold standard in the invasive hemodynamic assessment of epicardial coronary artery stenoses. FFR is defined as the ratio of maximal flow achievable in the stenotic coronary artery to the maximal flow achievable in the same coronary artery if it was normal. In other words, FFR informs the clinician to what extent blood flow is reduced and can be improved after revascularization: e.g., a FFR of 0.60 means that coronary blood flow is 60% of what should be in the absence of the epicardial stenosis, and it could improve by 40% after percutaneous coronary intervention.