iFR vs. FFR for coronary revascularization: safety and outcomes

Introduction Coronary revascularization guided by functional assessment has been shown to improve patient outcomes compared to revascularization guided by angiography alone. Randomized clinical trials have demonstrated that coronary revascularization guided by instantaneous wave-free ratio (iFR) is noninferior to fractional flow reserve (FFR) in terms of major adverse cardiac events at 1 year. However, the 5-year results of the DEFINE-FLAIR trial raised concerns due to an observed increase in all-cause mortality in the iFR arm, contrary to the iFR SWEDEHEART trial. The aim of this study is to validate the safety of performing iFR versus FFR in a large real-world long term dataset, focusing on major adverse cardiac events. Methods This retrospective, single-center, observational cohort study included patients undergoing coronary angiography guided by functional assessment from 2012 to 2022 in a tertiary center . Two groups were analyzed: patients assessed with FFR and those with iFR. Differences between the groups were evaluated using the chi-square, independent t-test or Mann-Whitney U test. Kaplan-Meier survival curves and Cox regression analysis were used to evaluate the primary composite outcome of death or myocardial infarction at two-year follow-up Results A total of 543 patients were included, with a mean age of 67±10 years; 77% were male. Of these, 161 underwent FFR and 382 underwent iFR. There were no significant differences between the groups in sex distribution, relevant comorbidities, or baseline left ventricular ejection fraction, except for a higher prevalence of previous smoking and chronic kidney disease in the iFR group. The most commonly evaluated vessel in both groups was the left anterior descending artery, followed by the right coronary artery and the circumflex artery. Medical therapy was more common in the iFR group (59% vs. 52%, p=0.02), and PCI was performed less frequently (32% vs. 42%, p=0.03). The mean procedure time was shorter in the iFR group (56 vs. 62 minutes, p=0.005), with lower radiation doses (6.4 ± 2.8 vs. 11.6 ± 4.6 Gy). The primary composite outcome of death or myocardial infarction occurred in 37 patients in the iFR group and 16 patients in the FFR group, with no significant difference between the groups. Similarly, no difference was observed in all-cause mortality (7.1% vs. 7.3%). Conclusion In this real-world cohort, no significant differences were observed in the primary composite outcome of death or myocardial infarction at two-year follow-up between patients undergoing coronary revascularization guided by iFR versus FFR. Although iFR was associated with shorter procedure times, lower radiation doses, and less frequent PCI, the safety profile of iFR appeared comparable to FFR, with no significant differences in all-cause mortality. This result is in agreement with the iFR Swedeheart trial, further strengthening the safety of using iFR for revascularization decisions.