CT Fractional Flow Reserve: A Practical Guide to Application, Interpretation, and Problem Solving.

CT fractional flow reserve (FFR) is a physiologic simulation technique that models coronary flow from routine coronary CT angiography (CTA). To evaluate lesion-specific ischemia, FFR is measured 2 cm distal to a stenotic lesion. FFR greater than 0.8 is normal, 0.76-0.8 is borderline, and 0.75 or less is abnormal. FFR should always be interpreted in correlation with clinical and anatomic coronary CTA findings. FFR increases the specificity of coronary CTA in the evaluation of coronary artery disease, decreases the prevalence of nonobstructive disease in invasive coronary angiography (ICA), and helps with revascularization decisions and planning. Patients with intermediate-risk coronary anatomy at CTA and abnormal FFR can undergo ICA and revascularization, whereas those with normal FFR can be safely deferred from ICA. In borderline FFR values, management is decided in the context of the clinical scenario, but many cases could be safely managed with medical treatment. There are some limitations and pitfalls of FFR. Abnormal FFR values can be seen in mild stenosis, and normal FFRvalues can be seen in severe stenosis. Gradually decreasing or abnormal low FFR values at the distal vessel without a proximal focal lesion could be due to diffuse atherosclerosis. Coronary stents, bypass grafts, coronary anomalies, coronary dissection, transcatheter aortic valve replacement, unstable angina, and acute or recent myocardial infarction are situations in which FFR has not been validated and should not be used at this time. The authors provide a practical guide to the applications and interpretation of FFR, focusing on common pitfalls and challenges. RSNA, 2022.