The assessment of functional severity of moderate coronary stenoses is challenging. Coronary angiography remains the standard technique for diagnosis, although, due to its limitations, it is frequently insufficient to detect relevant myocardial ischemia. Fractional flow reserve (FFR) is defined as the ratio between the mean hyperemic coronary artery pressure distal to the lesion and mean pressure in the aorta. The FFR measurement is currently supported by guidelines to evaluate the hemodynamic significance of lesions. Proper identification of patients that have the potential to benefit from revascularization is crucial. Based on already published literature, we focus on the long-term follow-up of patients with FFR-driven treatment. We also provide a review of specific clinical cases such as borderline FFR values, comorbidities or lesions in anatomical risk locations, in which interpretation can be challenging during the physiological assessment. The aim of this paper is to provide an overview of the evidence of FFR implementation in daily clinical practice and determine issues that raise doubts.
Keywords: coronary artery disease (CAD); fractional flow reserve (FFR); grey zone; medical therapy; revascularization.