Characteristics and correlation between FFR and RFR of non-culprit lesions in acute myocardial infarction

Abstract

Background: While resting-full cycle ratio (RFR) is strongly correlated with fractional flow reserve (FFR), it has been extensively examined in stable coronary artery disease. However, there is a lack of evaluation regarding non-culprit lesions in patients with acute myocardial infarction (AMI). Objectives: To investigate the clinical characteristics and to identify the correlation and discordance between FFR and RFR among AMI patients with non-culprit lesions. Methods: A retrospective cohort study was conducted in 44 AMI patients who underwent percutaneous coronary intervention (PCI) for culprit lesions and > 90% stenosis non-culprit lesions. With non-culprit stenosis from 50 - 90%, 23 patients had simultaneous measurements of both FFR and RFR, and 17 patients underwent PCI based on FFR ≤ 0.8. Results: Approximately 79.5% of patients exhibited a presence of two or more risk factors associated with coronary artery disease. In 44 culprit lesions, 40.9% of cases located in the RCA branch, while in 46 nonculprit lesions, 61.4% of cases were found in the LAD branch. The average FFR among 44 patients was 0.82 ± 0.13. There was a significant improvement in FFR after PCI (0.89 ± 0.07) compared to pre-PCI (0.70 ± 0.11) in 17 patients with p < 0.001. The mean RFR among the 23 patients was 0.84 ± 0.12. Among 12 patients with positive RFR, RFR after PCI (0.95 ± 0.04) was higher than pre-PCI (0.78 ± 0.13) with p = 0.002. Furthermore, pre-PCI RFR showed a strong positive correlation with FFR (r = 0.662, p = 0.001). The discordant rate between RFR and FFR was 26.8%. The discordant rate of FFR and RFR measurements was 26.1%. Additionally, the left anterior descending artery (LAD) was assumed as a predictor of discordance in the high FFR group (FFR > 0.80) and low RFR group (RFR ≤ 0.89). Conclusion: The low discordance rate and strong correlation between FFR and RFR suggest their complementary roles in the assessment of intermediate non-culprit lesions in patients with AMI. Key words: fractional flow reserve, resting full-cycle ratio, non-culprit lesion, correlation, acute myocardial infarction.