Combined assessment of fractional flow reserve, resting full-cycle ratio, and resting ratio of distal coronary to aortic pressure for clinical outcomes.

BACKGROUND: Fractional flow reserve (FFR) and non-hyperemic indices are invasive standards for evaluating functional significance of coronary stenosis. However, data are limited about outcomes in vessels with concordant and discordant physiological results, particularly with a ratio of distal coronary to aortic pressure (Pd/Pa) at rest. METHODS: This was a single-center, retrospective, observational study. Coronary physiological indices including FFR, resting full-cycle ratio (RFR), and resting Pd/Pa were invasively evaluated in vessels with intermediate coronary artery stenosis. FFR ≤0.80, RFR ≤0.89, and resting Pd/Pa ≤0.92 were considered physiologically positive. Vessels were divided into three groups according to the results of FFR, RFR, and resting Pd/Pa: concordant positive (all positive for FFR, RFR, and resting Pd/Pa), concordant negative (all negative for FFR, RFR, and resting Pd/Pa), and discordant groups. The primary endpoint was target vessel failure (TVF) defined as a composite of cardiac death and target vessel myocardial infarction and unplanned revascularization. RESULTS: Of 987 vessels included, 311 (31.5 %), 263 (26.6 %), and 413 (41.9 %) were in the concordant positive, discordant, and concordant negative groups. During a median follow-up period of 417 (208-756) days, TVF occurred more frequently in the concordant positive group, followed by the discordant and concordant negative groups (7.7 % vs. 4.6 % vs. 2.4 %, p = 0.004). TVF increasingly accrued during long-term follow-up, while discordant results of RFR and resting Pd/Pa did not result in worse outcomes compared with negative RFR and resting Pd/Pa. CONCLUSION: The combined assessment of FFR with RFR and resting Pd/Pa stratified TVF risks in vessels with intermediate coronary stenosis.

Comparison of Fractional Flow Reserve and Resting Full-Cycle Ratio in the Functional Assessment of Coronary Artery Stenosis in Patients with Non-ST-Segment Elevation Acute Coronary Syndrome.

Background: This study investigated factors influencing discrepancies between fractional flow reserve (FFR) and resting full-cycle ratio (RFR) in the functional assessment of coronary artery stenosis in patients with non-ST-segment elevation acute coronary syndrome (NSTE-ACS). Methods: We included 320 diseased vessels from 253 consecutive patients with NSTE-ACS. Vessels were categorized into four groups based on FFR ≤ 0.80 and RFR ≤ 0.89 thresholds: group 1 concordant negative (RFR-/FFR-), group 2 positive RFR and negative FFR (RFR+/FFR-), group 3 negative RFR and positive FFR (RFR-/FFR+), and group 4 concordant positive (RFR+/FFR+). Univariate and multivariate logistic regression analyses were conducted to identify predictors of diagnostic discrepancy between FFR and RFR. Results: Of the 320 diseased vessels, 182 (56.9%) were in group 1 (RFR-/FFR-), 33 (10.3%) in group 2 (RFR+/FFR-), 31 (9.7%) in group 3 (RFR-/FFR+), and 74 (23.1%) in group 4 (RFR+/FFR+). The concordance between FFR and RFR was 80.0%. Notably, left anterior descending artery (LAD) lesions exhibited significantly lower consistency compared to non-LAD lesions (p = 0.001), with distinct differences in FFR and RFR values between these groups (p < 0.001). The presence of a LAD lesion emerged as an independent predictor of diagnostic inconsistency between positive RFR and negative FFR measurements (p = 0.001). Conclusions: LAD involvement independently predicts diagnostic discrepancies between FFR and RFR in evaluating functional coronary artery stenosis in NSTE-ACS patients.

Diagnostic performance of resting full-cycle ratio in identifying coronary lesions causing myocardial ischaemia: a meta-analysis.

BACKGROUND: The resting full-cycle ratio (RFR), a new non-congestive resting index, is commonly used for physiological evaluations of coronary arteries. AIMS: This study aims to evaluate the accuracy of RFR in detecting coronary artery stenosis with hemodynamic significance using fractional flow reserve (FFR) as the reference standard. METHODS: Using 'RFR, resting full-cycle ratio' as the search term, we searched PubMed, Embase, Cochrane Library, and Web of Science databases, screening the literature according to the inclusion and exclusion criteria. By applying FFR ≤ 0.80 and RFR ≤ 0.89 as the diagnostic criteria for ischaemia, we analysed the synthetic sensitivity, specificity, and corresponding 95% confidence intervals, then synthesised the summary receiver operating characteristic curve (SROC). RESULTS: Three studies were included in this meta-analysis, comprising 1,084 patients with 1,312 lesions. When we used FFR ≤ 0.80 as the reference standard, the synthesised sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), positive likelihood ratio (LR+), and negative likelihood ratio (LR-) of RFR in the diagnosis of coronary ischaemia were 73%, 81%, 67%, 85%, 3.95, and 0.33, respectively. Besides, the area under the curve (AUC) was 0.8276. CONCLUSION: Using FFR as the reference standard, RFR has good diagnostic accuracy in detecting coronary ischaemic lesions and may be an effective alternative to FFR in the future, to some extent.

The Impact of Age on the Physiological Assessment of Borderline Coronary Stenoses.

Background and Objectives: Coronary angiography is the gold standard for diagnosing coronary artery disease (CAD). In the case of borderline changes, patients require further diagnosis through ischemia assessment via one of the recommended methods of invasive evaluation. This study aimed to assess whether clinical factors influence the risk of a positive result in invasive myocardial ischemia assessment and if these potential factors change with the patient's age and the consistency of ischemia assessment. Materials and Methods: Data were collected retrospectively on all consecutive patients hospitalized in the University Hospital in Krakow between 2020 and 2021, on whom physiological assessments of coronary circulation were performed. Patients were divided into two groups: patients aged 60 or younger and patients older than 60. Results: Despite the older patients having more risk factors for CAD, their physiological assessment results of borderline lesions were similar to those of the younger patients. Positive fractional flow reserve (FFR) assessments were obtained from almost 50% of vessels. In the younger patients, cigarette use and type 2 diabetes mellitus increased the risk of a positive FFR result by 3.5 and 2.5 times, respectively. In the older patients, male gender and peripheral vascular disease significantly increased the risk of a positive FFR by 2.5 and 2 times, respectively. Conclusions: Clinical characteristics of patients undergoing physiological assessment of borderline coronary stenosis varied significantly by age. Refining the definition of borderline lesions to include age, gender, and other factors may improve the identification of patients who would benefit from physiological assessment and coronary revascularization.

Comparison of quantitative flow ratio with instantaneous wave-free ratio and resting full-cycle ratio during daily routine in the catheterization laboratory.

BACKGROUND: Quantitative flow ratio (QFR) is a novel, software-based method to evaluate the physiology of coronary lesions. The aim of this study was to compare QFR with the established invasive measurements of coronary blood flow using instantaneous wave-free ratio (iFR) or resting full-cycle ratio (RFR) in daily cathlab routine. METHODS: 102 patients with stable coronary artery disease and a coronary stenosis of 40%-90% were simultaneously assessed with QFR and iFR or RFR. QFR-computation was performed by two certified experts using the appropriate software (QAngio XA 3D 3.2). RESULTS: QFR showed a significant correlation (r = 0.75, p < 0.001) to iFR and RFR. The area under the receiver curve for all measurements was 0.93 (95% confidence interval, 0.87-0.98) for QFR compared to iFR or RFR. QFR based assessment required less time with a median of 501 s (IQR 421-659 s) compared to iFR or RFR which required a median of 734 s to obtain the result (IQR 512-967 s; p < 0.001). The median use of contrast medium was similar with 21 mL (IQR 16-30 mL) for the QFR-based and 22 mL (IQR 15-35 mL) for the iFR- or RFR-based diagnostic. QFR diagnostic required less radiation. The median dose area product for QFR was 307cGycm2 (IQR 151-429 cGycm2 ) compared to 599 cGycm2 (IQR 345-1082 cGycm2 ) for iFR or RFR, p < 0.001. CONCLUSION: QFR measurements of coronary artery blood flow correlate with iFR or RFR measurements and are associated with shorter procedure times and reduced radiation dose.

The Influence of Microcirculatory Dysfunction on the Resting Full Cycle Ratio Compared to Fractional Flow Reserve.

BACKGROUND: The relation between the resting full cycle ratio (RFR) and fractional flow reserve (FFR) is not fully understood. This study aims to investigate the influence of coronary microvascular dysfunction, assessed by the index of microvascular resistance (IMR), on RFR compared to FFR in patients undergoing functional assessment for coronary stenosis. MATERIALS AND METHODS: Two-hundred patients with borderline stenosis underwent functional assessment of RFR, FFR, coronary flow reserve (CFR) and IMR. Retriever operator curve analysis was performed to assess the diagnostic value of RFR in patients with (IMR ≥ 24) and (IMR < 24). RESULTS: Median RFR did not differ significantly in patients with IMR ≥ 24 compared to patients with IMR < 24: 0.89 (interquartile range (IQR) 0.84, 0.95) vs. 0.90 (IQR 0.84, 0.92), p = 0.29). FFR was significantly higher in patients with IMR ≥ 24 compared to patients with IMR < 24: median FFR 0.85 (IQR (0.76, 0.92)) vs. 0.82 (IQR 0.73, 0.86), p = 0.009, and median CFR was significantly lower 1.80 (IQR 1.40, 2.55) vs. 2.70 (IQR 1.80, 3.95), p < 0.001. The diagnostic value of RFR was high (Area under the curve (AUC) 0.89 95 % Confidence Interval: [0.85, 0.93]) and AUC did not differ between patients with IMR ≥ 24 compared to patients with IMR < 24: 0.89 vs. 0.90, p = 0.89. An overall optimal cut off of 0.88 was identified. The cut off did not differ significantly between patients with IMR ≥ 24 compared to patients with IMR < 24: 0.88 vs. 0.90, p = 0.397. CONCLUSION: In patients with coronary borderline stenosis, the coronary microvascular function did not influence on the cut off values or AUC of RFR compared to FFR.

The reliability and utility of on-site CT-derived fractional flow reserve (FFR) based on fluid structure interactions: comparison with FFRCT based on computational fluid dynamics, invasive FFR, and resting full-cycle ratio.

Fractional flow reserve (FFR) derived off-site by coronary computed tomography angiography (CCTA) (FFRCT) is obtained by applying the principles of computational fluid dynamics. This study aimed to validate the overall reliability of on-site CCTA-derived FFR based on fluid structure interactions (CT-FFR) and assess its clinical utility compared with FFRCT, invasive FFR, and resting full-cycle ratio (RFR). We calculated the CT-FFR for 924 coronary vessels in 308 patients who underwent CCTA for clinically suspected coronary artery disease. Of these patients, 35 patients with at least one obstructive stenosis (> 50%) detected on CCTA underwent both CT-FFR and FFRCT for further investigation. Furthermore, 24 and 20 patients underwent invasive FFR and RFR in addition to CT-FFR, respectively. The inter-observer correlation (r) of CT-FFR was 0.93 (95% confidence interval [CI] 0.85-0.97, P < 0.0001) with a mean absolute difference of - 0.0042 (limits of agreement - 0.073, 0.064); 97.3% of coronary arteries without obstructive lesions on CCTA had negative results for ischemia on CT-FFR (> 0.80). The correlation coefficient between CT-FFR and FFRCT for 105 coronary vessels was 0.87 (95% CI 0.82-0.91, P < 0.0001) with a mean absolute difference of - 0.012 (limits of agreement - 0.12, 0.10). CT-FFR correlated well with both invasive FFR (r = 0.66, 95% CI 0.36-0.84, P = 0.0003) and RFR (r = 0.78, 95% CI 0.51-0.91, P < 0.0001). These data suggest that CT-FFR can potentially substitute for FFRCT and correlates closely with invasive FFR and RFR with high reproducibility. Our findings should be proven by further clinical investigation in a larger cohort.

Impact of Left Ventricular Outflow Tract Obstruction on Coronary Physiological Assessment.

Hypertrophic cardiomyopathy which is known to occasionally have coronary artery disease as concomitant disease may require coronary physiological assessment (Okayama et al., 2015; Shin et al., 2019 [1,2]). However, no study clarified the impact of left ventricular outflow tract obstruction on coronary physiological assessment. Herein, a case of hypertrophic obstructive cardiomyopathy concomitant with moderate coronary lesion was reported, in which dynamic change of physiological values was observed during pharmacological intervention. Specifically, fractional flow reserve (FFR) and resting full-cycle ratio (RFR) changed in an opposite fashion when the left ventricular outflow tract pressure gradient was decreased by intravenous propranolol and cibenzoline: in FFR from 0.83 to 0.79 and in RFR from 0.73 to 0.91. Cardiologists should pay attention to the presence of concomitant cardiovascular disorders in interpreting coronary physiological data.

Adenosine-Induced Atrial Fibrillation During Coronary Angiography and Fractional Flow Reserve Procedures.

A woman in her sixties presented with a history of progressive shortness of breath, palpitations, and feeling of chest heaviness for the last eight months. To rule out underlying obstructive coronary artery disease, an invasive cardiac catheterization was planned. To assess the hemodynamic significance of the lesion, resting full cycle ratio (RFR) and fractional flow reserve (FFR) values were measured. During this procedure, almost immediately after starting IV adenosine infusion, the patient went into atrial fibrillation which was reversed by IV aminophylline. Awareness of this uncommon effect of adenosine on the cardiac electrical pathways merits knowledge and a thorough follow-up testing of these patients is justified.

Comparison of Fractional Flow Reserve with Resting Non-Hyperemic Indices in Patients with Coronary Artery Disease.

Guidelines recommend using hyperemic (FFR) and non-hyperemic (iFR/RFR) methods of evaluating coronary artery stenoses in patients with coronary artery disease. However, in some cases, achieved results indicating significant ischemia may differ between those methods. Thus, we sought to identify predictors of such a discrepancy. Data were collected on all consecutive patients with chronic coronary syndrome hospitalized between 2020 and 2021. For 279 patients (417 vessels), results for both FFR and iFR/RFR were available. Values of ≤0.80 for FFR and ≤0.89 for iFR/RFR were considered positive for ischemia. Discordant measurements of FFR and iFR/RFR were observed in 80 (19.2%) patients. Atrial fibrillation was the only predictor of the overall FFR and iFR/RFR discordance - OR (95%CI) 1.90 (1.02-3.51); p = 0.040. The chance of positive FFR and negative iFR/RFR decreased independently with age - OR (95%CI) 0.96 (0.93-0.99); p = 0.024. On the contrary, insulin-treated diabetes mellitus was the predictor of negative FFR and positive iFR/RFR discrepancy - OR (95%CI) 4.61 (1.38-15.40); p = 0.013. In everyday clinical practice, iFR/FFR correlates well with FFR. However, discordance between these methods is quite common. Physicians should be aware of the risk of such discordance in patients with atrial fibrillation, advanced age, and insulin-treated diabetes mellitus.

Going under the bridge: unmasking ischaemia and endothelial dysfunction of myocardial bridging: a case report.

Background: Physiological assessment of myocardial bridging prevents unnecessary interventions. Non-invasive workup or visual coronary artery compression may underestimate the underlying ischaemia associated with myocardial bridging in symptomatic patients. Case summary: A 74-year-old male presented to the outpatient clinic with chest pain and shortness of breath on exertion. He underwent coronary artery calcium scan showing an elevated calcium score of 404. On follow-up, he endorsed progressive worsening of symptoms with chest pain and decreased exercise tolerance. He was then referred for coronary angiography that revealed mid-left anterior descending myocardial bridging with initial normal resting full-cycle ratio of 0.92. Further workup after ruling out coronary microvascular disease demonstrated abnormal hyperaemic full-cycle ratio of 0.80 with a diffuse rise across the myocardial bridging segment on pullback. Our patient also had increased spastic response to hyperaemia on angiography, supporting the presence of underlying endothelial dysfunction and ischaemia, likely contributing to his exertional symptomology. The patient was started on beta-blocker therapy with improvement in symptoms and resolution of chest pain on follow-up. Conclusion: Our case highlights the importance of thorough workup of myocardial bridging in symptomatic patients to better understand the underlying physiology and endothelial function after ruling out microvascular disease and consideration of hyperaemic testing if symptoms are suggestive of ischaemia.

Prognostic impact of resting full-cycle ratio and diastolic non-hyperemic pressure ratios in patients with deferred revascularization.

BACKGROUND: Non-hyperemic pressure ratios (NHPRs) like resting full-cycle ratio (RFR), diastolic pressure ratio during entire diastole (dPR[entire]) and diastolic pressure ratio during wave-free period (dPR[WFP]) are increasingly used to guide revascularization. The effect of NHPRs on mid-term prognosis has not been well established. OBJECTIVE: We investigated the prognostic implications of NHRPs in patients whose revascularization was deferred based on fractional flow reserve (FFR) in a single-centre population. METHODS: NHPRs and FFR were calculated offline from pressure tracings by an independent core laboratory. Follow-up data were acquired through records of hospital visits or telephone interviews. The primary outcome was a vessel-oriented composite outcome (VOCO) (a composite of cardiac death, vessel-related myocardial infarction, and ischemia-driven revascularization) in deferred vessels at 2 years. RESULTS: 316 patients with 377 deferred lesions were analysed. Discordance of NHPRs and FFR was found in 13.0-18.3% of lesions. The correlation coefficient between NHPRs was 0.99 (95% confidence interval 0.99-1.00). At 2 years, VOCO occurred in 19 lesions (5.0%). Estimated glomerular filtration rate < 30 mL/min/1.73 m2 [hazard ratio (HR) 5.7, p = 0.002], previous myocardial infarction (HR 3.3, p = 0.018), diabetes (HR 2.7, p = 0.042), RFR ≤ 0.89 (HR 2.7, p = 0.041) and dPR[WFP] ≤ 0.89 (HR 2.7, p = 0.049) were associated with higher incidence of VOCO at 2 years in the univariable analysis. A non-significant trend was found for dPR[entire] (HR 1.9, p = 0.26). CONCLUSION: A positive RFR or dPR[WFP] were associated with a worse prognosis in deferred lesions, suggesting that the use of NHPRs in addition to FFR may improve risk estimation.

Comparison of vessel fractional flow reserve with invasive resting full-cycle ratio in patients with intermediate coronary lesions.

BACKGROUND: Vessel fractional flow reserve (vFFR) is a novel angiography-derived index for the assessment of myocardial ischemia without the need for pressure wires and hyperemic agents. vFFR has demonstrated very good diagnostic performance compared with the hyperemic index fractional flow reserve (FFR). The aim of this study was to compare vFFR to the non-hyperemic pressure ratio resting full-cycle ratio (RFR). METHODS: This was a retrospective, observational, single-center study of an all-comer cohort undergoing RFR assessment. Invasive coronary angiography was obtained without a dedicated vFFR acquisition protocol, and vFFR calculation was attempted in all vessels interrogated by RFR (1483 lesions of 1030 patients). RESULTS: vFFR could be analyzed in 986 lesions from 705 patients. Median diameter stenosis was 37% (interquartile range (IQR): 30.0-44.0%), vFFR 0.86 (IQR: 0.81-0.91) and RFR 0.94 (IQR: (0.90-0.97). The correlation between vFFR and RFR was strong (r = 0.70, 95% confidence interval (CI): 0.66-0.74, p < 0.001). Using RFR ≤0.89 as reference, the sensitivity, specificity, positive predictive value, negative predictive value, and overall diagnostic accuracy for vFFR were 77%, 93%, 77%, and 92% and 89%. vFFR yielded a high area under the curve (AUC) of 0.92 (95% CI: 0.90-0.94). The good diagnostic performance of vFFR was confirmed among subgroups of patients with diabetes, severe aortic stenosis, female gender and lesions located in the left anterior descending artery. CONCLUSION: vFFR has a high diagnostic performance taking RFR as the reference standard for evaluating the functional significance of coronary stenoses.

Clinical assessment of resting full-cycle ratio and fractional flow reserve for coronary artery disease in a real-world cohort.

Background: There are few reports published on the comparison of the resting full-cycle ratio (RFR) and fractional flow reserve (FFR) on the assessment of the severity of coronary stenosis. We aimed to investigate the diagnostic accuracy of RFR for detection of functionally significant coronary lesions. Methods: This was an observational, retrospective, single-center study. We evaluated both RFR and FFR for 277 coronary lesions of 235 patients who underwent coronary angiography. Patients presenting with chronic coronary syndrome, unstable angina, or non-ST-elevation myocardial infarction were included. Results: The mean FFR and RFR values were 0.84 ± 0.08 and 0.90 ± 0.08, respectively. RFR significantly correlated with FFR (r = 0.727, P < 0.001). The agreement rate between the FFR and RFR was 79.8% (221/277). The diagnostic performance of RFR vs. FFR was accuracy 79.8%, sensitivity 70.4%, specificity 83.7%, positive predictive value 64.0%, and negative predictive value 87.2%. The discriminative power of RFR to identify lesions with FFR ≤ 0.80 was acceptable when the RFR value was within the gray zone [0.86 ≤ RFR ≤ 0.93; AUC: 0.72 (95% CI:0.63-0.81)], while it was excellent when the RFR value was out of the gray zone [RFR > 0.93 or < 0.86; AUC: 0.94 (95% CI:0.88-0.99)]. Conclusion: RFR was significantly correlated with FFR in the assessment of intermediate coronary stenosis. An RFR-FFR hybrid approach increases the diagnostic accuracy of RFR in the detection of functionally significant lesions.

Ajustando a RFR por Preditores de Discordância, "A RFR Ajustada": Uma Metodologia Alternativa para Melhorar a Capacidade Diagnóstica dos Índices Coronarianos / Adjusting RFR by Predictors of Disagreement, "The Adjusted RFR": An Alternative Methodology to Improve the Diagnostic Capacity of Coronary Indices

Resumo Fundamento Os limiares de corte para a "relação do ciclo completo de repouso" (RFR) oscilam em diferentes séries, sugerindo que as características da população podem influenciá-los. Da mesma forma, foram documentados preditores de discordância entre a RFR e a reserva de fluxo fracionado (FFR). O Estudo RECOPA, mostrou que a capacidade diagnóstica está reduzida na "zona cinzenta" da RFR, tornando necessária a realização de FFR para descartar ou confirmar isquemia. Objetivos Determinar os preditores de discordância, integrar as informações que eles fornecem em um índice clínico-fisiológico: a "RFR Ajustada", e comparar sua concordância com o FFR. Métodos Usando dados do Estudo RECOPA, os preditores de discordância em relação à FFR foram determinados na "zona cinzenta" da RFR (0,86 a 0,92) para construir um índice ("RFR Ajustada") que pesaria a RFR juntamente com os preditores de discordância e avaliar sua concordância com a FFR. Resultados Foram avaliadas 156 lesões em 141 pacientes. Os preditores de discordância foram: doença renal crônica, cardiopatia isquêmica prévia, lesões não envolvendo a artéria descendente anterior esquerda e síndrome coronariana aguda. Embora limitada, a "RFR Ajustada" melhorou a capacidade diagnóstica em comparação com a RFR na "zona cinzenta" (AUC-RFR = 0,651 versus AUC-"RFR Ajustada" = 0,749), mostrando também uma melhora em todos os índices diagnósticos quando foram estabelecidos limiares de corte otimizados (sensibilidade: 59% a 68%; especificidade: 62% a 75%; acurácia diagnóstica: 60% a 71%; razão de verossimilhança positiva: 1,51 a 2,34; razão de verossimilhança negativa: 0,64 a 0,37). Conclusões Ajustar a RFR integrando as informações fornecidas pelos preditores de discordância para obter a "RFR Ajustada" melhorou a capacidade diagnóstica em nossa população. Mais estudos são necessários para avaliar se os índices clínico-fisiológicos melhoram a capacidade diagnóstica da RFR ou de outros índices coronarianos.

Abstract Background Cutoff thresholds for the "resting full-cycle ratio" (RFR) oscillate in different series, suggesting that population characteristics may influence them. Likewise, predictors of discordance between the RFR and fractional flow reserve (FFR) have been documented. The RECOPA Study showed that diagnostic capacity is reduced in the RFR "grey zone", requiring the performance of FFR to rule out or confirm ischemia. Objectives To determine predictors of discordance, integrate the information they provide in a clinical-physiological index, the "Adjusted RFR", and compare its agreement with the FFR. Methods Using data from the RECOPA Study, predictors of discordance with respect to FFR were determined in the RFR "grey zone" (0.86 to 0.92) to construct an index ("Adjusted RFR") that would weigh RFR together with predictors of discordance and evaluate its agreement with FFR. Results A total of 156 lesions were evaluated in 141 patients. Predictors of discordance were: chronic kidney disease, previous ischemic heart disease, lesions not involving the anterior descending artery, and acute coronary syndrome. Though limited, the "Adjusted RFR" improved the diagnostic capacity compared to the RFR in the "grey zone" (AUC-RFR = 0.651 versus AUC-"Adjusted RFR" = 0.749), also showing an improvement in all diagnostic indices when optimal cutoff thresholds were established (sensitivity: 59% to 68%; specificity: 62% to 75%; diagnostic accuracy: 60% to 71%; positive likelihood ratio: 1.51 to 2.34; negative likelihood ratio: 0.64 to 0.37). Conclusions Adjusting the RFR by integrating the information provided by predictors of discordance to obtain the "Adjusted RFR" improved the diagnostic capacity in our population. Further studies are required to evaluate whether clinical-physiological indices improve the diagnostic capacity of RFR or other coronary indices.

The impact of coronary microvascular dysfunction on the discordance between fractional flow reserve and resting full-cycle ratio in patients with chronic coronary syndromes.

Background: Resting full-cycle ratio (RFR) is an alternative to fractional flow reserve (FFR) for the evaluation of borderline coronary artery lesions. Although FFR and RFR results are discordant in some cases, factors associated with the discordance remain unclear. The role of coronary microvascular dysfunction (CMD) is discussed as a potential mechanism to explain these discrepancies. Aim: The study aimed to assess concordance between RFR and FFR in a real-life cohort from a high-volume center regarding the role of CMD. Methods: Consecutive patients with borderline coronary lesions undergoing coronary functional testing for chronic coronary syndromes were included in the study. Measurements of RFR and FFR were performed alongside additional coronary flow reserve (CFR), resistance reserve ratio (RRR), and an index of microcirculatory resistance (IMR) measurements. CMD was defined according to the current guideline by either IMR ≥25 or CFR ≤2.0 in vessels with no significant stenosis. Results: Measurements were performed in 157 coronary arteries, in 101 patients, with a median age of 66 y., 74% male, with prior history of arterial hypertension (96%), dyslipidaemia (91%), and diabetes (40%). The median value of vessel diameter stenosis was 45% according to QCA.Overall, FFR and RFR values were significantly correlated (r = 0.66, p < 0.001), where positive FFR/negative RFR and negative FFR/positive RFR were observed in 6 (3.8%) and 38 (24.2%) of 157 vessels. The RFR/FFR discrepancy was present in 44 (28%) of measurements. CMD was confirmed in 28 (64%) of vessels with discrepant RFR/FFR and in 46 (41%) of vessels with concordant results (p = 0.01). In discordant RFR/FFR vessels, as compared to concordant ones, significantly lower values of CFR [median 1.95 (IQR: 1.37, 2.30) vs. 2.10 (IQR: 1.50, 3.00), p = 0.030] and RRR [median 2.50 (IQR: 1.60, 3.10) vs. 2.90 IQR (1.90, 3.90), p = 0.048] were observed.Main predictors of RFR/FFR discrepancy in a univariate regression analysis were: higher age of patients [OR = 1.06 (1.01; 1.10), p = 0.010], presence of CMD [OR = 2.51 (1.23; 5.25), p = 0.012], lower CFR [OR = 1.64 (1.12; 2.56), p = 0.018], and lower RRR values [OR = 1.35 (95% CI: 1.03; 1.83), p = 0.038]. Conclusion: In discrepant RFR/FFR vessels, CMD is more prevalent than in concordant RFR/FFR measurements, which can be driven by lower CFR or RRR values. Further research is needed to confirm this observation.

The guiding value of hybrid resting full-cycle ratio and fractional flow reserve strategy for percutaneous coronary intervention in a Chinese real-world cohort with non-ST elevation acute coronary syndrome.

Objective: The study aimed to assess the correlation and agreement between resting full-cycle ratio (RFR) and fractional flow reserve (FFR), and evaluate the guiding value of a hybrid RFR-FFR strategy for percutaneous coronary intervention (PCI) in a Chinese real-world cohort with non-ST elevation acute coronary syndrome (NSTE-ACS). Materials and methods: A total of 109 patients with NSTE-ACS (149 diseased vessels), who underwent an invasive physiological assessment in Cangzhou Central Hospital, Hebei Medical University, were prospectively enrolled from September 2021 to May 2022. FFR ≤ 0.80 was used as the gold standard for coronary artery functional ischemia. We utilized the Pearson correlation and Bland-Altman analysis to assess the correlation and agreement between RFR and FFR. The diagnostic value of RFR predicting FFR ≤ 0.80 was evaluated in accordance with the receiver operating characteristic (ROC) curve. The hybrid RFR-FFR strategy, which was established according to determining the "gray zone" of RFR (FFR was further assessed using vasodilators only for diseased vessels in the "gray zone"), needed to afford over 95% global agreement with the FFR-only strategy. Results: Resting full-cycle ratio was significantly linearly linked with FFR (R 2 = 0.636, P < 0.001). The accuracy, specificity, and sensitivity for RFR ≤ 0.89 predicting FFR ≤ 0.80 were 81.2, 70.8, and 86.1%, respectively. The area under the ROC curve for RFR predicting FFR ≤ 0.80 was 0.881 (P < 0.001), and the cutoff value was 0.90. The "gray zone" of RFR was 0.85-0.93. The positive and negative predictive values of the hybrid RFR-FFR strategy were 0.95 and 0.93, respectively. The hybrid RFR-FFR strategy exhibited an agreement of 96.0% with FFR and obviated the need for a vasodilator by 60.4%. Conclusion: Resting full-cycle ratio and FFR have high correlation and consistency. The hybrid RFR-FFR strategy highlights considerably enhanced agreement with the FFR-only strategy, whilst making the requirement of vasodilator administration less than a half.

Differential Impact of Renal Function on the Diagnostic Performance of Resting Full-Cycle Ratio in Patients With Renal Dysfunction.

Background: Physiological assessments using fractional flow reserve (FFR) and resting full-cycle ratio (RFR) have been recommended for revascularization decision making. Previous studies have shown a 20% rate of discordance between FFR and RFR. In this context, the correlation between RFR and FFR in patients with renal dysfunction remains unclear. This study examined correlations between RFR and FFR according to renal function. Methods and Results: In all, 263 consecutive patients with 370 intermediate lesions were enrolled in the study. Patients were classified into 3 groups according to renal function: Group 1, estimated glomerular filtration rate (eGFR) ≥60 mL/min/1.73 m2; Group 2, 30 mL/min/1.73 m2≤eGFR<60 mL/min/1.73 m2; Group 3, eGFR <30 mL/min/1.73 m2. The discordance between FFR and RFR was assessed using known cut-off values for FFR (≤0.80) and RFR (≤0.89). Of the 370 lesions, functional significance with FFR was observed in 154 (41.6%). RFR was significantly correlated with FFR in all groups (Group 1, R2=0.62 [P<0.001]; Group 2, R2=0.67 [P<0.001]; Group 3, R2=0.46 [P<0.001]). The rate of discordance between RFR and FFR differed significantly among the 3 groups (Group 1, 18.8%; Group 2, 18.5%; Group 3, 42.9%; P=0.02). Conclusions: The diagnostic performance of RFR differed based on renal function. A better understanding of the clinical factors contributing to FFR/RFR discordance, such as renal function, may facilitate the use of these indices.

Futuristic robotic percutaneous coronary intervention with innovative physiology optimization: a case report.

Background: Robotic percutaneous coronary intervention (R-PCI) is being preferred over traditional PCI procedures owing to reduced radiation exposure to the personnel performing this technique. However, there are some challenges in using pressure wires in R-PCI. Case summary: This is the first article reporting the usage of pressure wire navigation in R-PCI. We have discussed a case of severe mid-right coronary artery disease, managed with physiology-assisted R-PCI. Software features of R-PCI such as Rotate-On-Retract were effectively used to negotiate Pressure Wire™ X across the tortuous artery. Stenting was successfully carried out with Pressure Wire™ X/R-PCI without any adverse events during or after the procedure. Discussion: Pressure Wire™ X was used with certain modifications to negotiate tortuous arteries. The R-PCI procedure was carried out successfully without any adverse events during or after the procedure.