How and When to Use Fractional Flow Reserve in Coronary Artery Bypass Grafting

I. Fractional flow reserve and instantaneous wave-free ratio for percutaneous coronary interventionFractional flow reserve (FFR) and instantaneous wave-free ratio (iFR) are pivotal tools in the assessment of coronary artery disease (CAD) and play crucial roles in guiding percutaneous coronary intervention (PCI).The FFR, defi ned as the ratio of the maximum blood fl ow in a diseased artery to the maximum fl ow in a normal artery, provides a quantitative measure of the physiological significance of coronary lesions.It is determined during coronary angiography by measuring the pressure both distal and proximal to the stenosis, allowing clinicians to assess whether a lesion is likely to benefi t from intervention 1) .The use of the FFR has been substantiated by numerous studies that have demonstrated its ability to improve outcomes in patients undergoing PCI.The fractional fl ow reserve versus angiography for multivessel evaluation (FAME) trial, for instance, showed that FFR-guided PCI resulted in lower rates of major adverse cardiovascular events relative to angiography alone 2) .These findings underscore the importance of the FFR in identifying functionally signifi cant lesions, thus optimizing patient selection for PCI.In contrast, iFR is a pressure-derived index that does not require adenosine-induced hyperemia.It measures the pressure difference during a wave-free period of diastole when coronary flow is predominantly controlled by coronary microcirculation rather than by the resistance of epicardial vessels.This technique provides a simpler and quicker alternative to evaluation of the FFR, especially in patients who may not tolerate adenosine well 3) .The iFR-SWEDEHEART trial demonstrated that iFR-guided PCI is non-inferior to FFR-guided PCI in terms of major adverse cardiac events 4) .This fi nding supports the use of iFR as a reliable alternative to the FFR in clinical practice, especially in situations in which time or patient tolerance is a concern.Both FFR and iFR have transformed the approach to CAD management by allowing a more tailored intervention strategy.They facilitate the identifi cation of patients who are likely to benefi t from revascularization, while helping to avoid unnecessary procedures in those with non-significant lesions.As these technologies continue to evolve, they are expected to enhance the effi cacy and safety of PCI and ultimately improve patient outcomes.According to the guidelines, testing the degree of functional stenosis based on parameters such as FFR and iFR for moderately stenotic lesions is a class 1 recommendation 5) .Furthermore, in PCI, performing multivessel revascularization using the FFR as a guide is class 2a recommendatio 5) .