53 Impact of coronary lesion location on the diagnostic accuracy of resting full-cycle ratio when compared to the standard fractional flow reserve

Introduction Functional Flow Reserve (FFR) is the standard for haemodynamic assessment of intermediate-grade coronary stenosis. The current focus of research is on developing adenosine-free indices for hemodynamic assessment to reduce costs and patient discomfort. The study aims to evaluate the diagnostic accuracy of resting full-cycle ratio (RFR), a non-hyperaemic index, for assessing coronary stenosis severity in different coronary vessels compared to FFR, particularly in proximal lesions with a critical prognosis. Method This retrospective observational study, conducted at Royal Albert Edward Infirmary, assesses intermediate-grade coronary lesions (40–90% stenosis) using non-hyperaemic RFR followed by FFR measured during maximal hyperaemia with adenosine. The study included patients with stable angina or acute coronary syndrome (ACS). Baseline demographic data was recorded, and the study received ethical approval. Invasive coronary angiography involved pressure sensor guidewire measurements, nitroglycerine administration, and RFR assessment. Adenosine-induced hyperaemia preceded FFR measurement. Lesion characteristics were defined using angiographic views, SYNTAX criteria, and ACC/AHA lesion classification. Primary focus was on the impact of lesion location and type on RFR-FFR discordance. Secondary endpoints included overall RFR-FFR correlation and determining the optimal RFR cut-off related to FFR≤0.80. Statistical analysis was performed with SPSS, describing variables, using Mcnemar test, Kappa, correlation coefficients, and ROC curve analysis for accuracy assessment. Bland-Altman plot and McNemar test evaluate RFR-FFR agreement. A p-value <0.001 was deemed to be significant. Results This study included 362 patients with intermediate-grade coronary stenosis, predominantly male (70.7%) with a mean age of 65.43 years. Most patients presented with stable CAD (75.1%). RFR and FFR values were 0.90 ± 0.07 and 0.82 ± 0.08, respectively, with significant correlation (r = 0.787, p < 0.001). ROC analysis indicated an AUC of 0.892 for RFR in relation to FFR (≤0.80), with a cut-off value of ≤0.89 (sensitivity 72.93%, specificity 90.91%). Lesion location impacted diagnostic accuracy; the lowest correlation was observed in LM/p LAD (r. 0.574) and LCX (r. 0.581) (figure 1). RFR accuracy was lowest for LCX (72.48%) and LM/p LAD (73.12%) at ≤0.89 cut-offs, highest for RCA lesions. No significant difference in RFR accuracy was found among lesion types (A, B1, B2). Discordant readings (48) were categorised into RFR positive/FFR negative (3.7%), FFR positive/RFR negative (5.2%), and both negative with positive Pd/Pa (1.5%). LM-pLAD, Other LAD lesions, LCX vessels, proximal, and distal lesion segments predicted negative RFR/positive FFR discordance (p < 0.001) (figure 2). Conclusion RFR has a good overall correlation with the standard FFR for functional assessment of intermediate-grade coronary stenosis at a cut-off of ≤0.89. However, the accuracy of this cut-off value seems to be influenced by lesion location, particularly LM/pLAD. That may be due to the large territory supplied by the LAD and may be significantly affected by the hyperaemic induction. Further studies with larger patient cohort would be needed to further validate these findings. Conflict of Interest No