The association between O2-pulse slope ratio and functional severity of coronary stenosis: A combined cardiopulmonary exercise testing and quantitative flow ratio study

Background

The role of cardiopulmonary exercise testing (CPET) parameters in evaluating the functional severity of coronary disease remains unclear. The aim of this study was to quantify the O2-pulse morphology and investigate its relevance in predicting the functional severity of coronary stenosis, using Murray law-based quantitative flow ratio (μQFR) as the reference.

Methods

CPET and μQFR were analyzed in 138 patients with stable coronary artery disease (CAD). The O2-pulse morphology was quantified through calculating the O2-pulse slope ratio. The presence of O2-pulse plateau was defined according to the best cutoff value of O2-pulse slope ratio for predicting μQFR ≤ 0.8.

Results

The optimal cutoff value of O2-pulse slope ratio for predicting μQFR ≤ 0.8 was 0.4, with area under the curve (AUC) of 0.632 (95 % CI: 0.505-0.759, p = 0.032). The total discordance rate between O2-pulse slope ratio and μQFR was 27.5 %, with 13 patients (9.4 %) being classified as mismatch (O2-pulse slope ratio > 0.4 and μQFR ≤ 0.8) and 25 patients being classified as reverse-mismatch (O2-pulse slope ratio ≤ 0.4 and μQFR > 0.8). Angiography-derived microvascular resistance was independently associated with mismatch (OR 0.07; 95 % CI: 0.01-0.38, p = 0.002) and reverse-mismatch (OR 9.76; 95 % CI: 1.47-64.82, p = 0.018).

Conclusion

Our findings demonstrate the potential of the CPET-derived O2-pulse slope ratio for assessing myocardial ischemia in stable CAD patients.

Geographic disparity of pathophysiological coronary artery disease characteristics: Insights from ASET trials

BACKGROUND

The geographical disparity in the pathophysiological pattern of coronary artery disease (CAD) among patients undergoing percutaneous coronary intervention (PCI) is unknown.

OBJECTIVES

To elucidate the geographical variance in the pathophysiological characteristics of CAD.

METHODS

Physiological indices derived from angiography-based fractional flow reserve pullbacks from patients with chronic coronary syndrome enrolled in the ASET Japan (n = 206) and ASET Brazil (n = 201) studies, which shared the same eligibility criteria, were analysed. The pathophysiological patterns of CAD were characterised using Murray law-based quantitative flow ratio (μQFR)-derived indices acquired from pre-PCI angiograms. The diffuseness of CAD was defined by the μQFR pullback pressure gradient index.

RESULTS

Significant functional stenoses pre-PCI (μQFR ≤0.80) were more frequent in ASET Japan compared to ASET Brazil (89.9% vs. 67.5%, p < 0.001), as were rates of a post-PCI μQFR <0.91 (22.1% vs. 12.9%, p = 0.013). In the multivariable analysis, pre-procedural μQFR and diffuse disease were independent factors for predicting a post-PCI μQFR <0.91, which contributed to the different rates of post-PCI μQFR ≥0.91 between the studies. Among vessels with a post-PCI μQFR <0.91, a consistent diffuse pattern of CAD pre- and post-PCI occurred in 78.3% and 76.7% of patients in ASET Japan and Brazil, respectively; only 6.3% (Japan) and 10.0% (Brazil) of vessels had a major residual gradient. Independent risk factors for diffuse disease were diabetes mellitus in ASET Japan, and age and male gender in Brazil.

CONCLUSIONS

There was geographic disparity in pre-procedural angiography-based pathophysiological characteristics. The combined pre-procedural physiological assessment of vessel μQFR and diffuseness of CAD may potentially identify patients who will benefit most from PCI.

Comparison among various physiology and angiography-guided strategies for deferring percutaneous coronary intervention: A network meta-analysis

BACKGROUND/PURPOSE

It is unclear whether coronary physiology or coronary angiography (CA)-guided strategy is the more preferable approach for deferring percutaneous coronary intervention (PCI). We sought to evaluate the clinical efficacy of various PCI strategies through a network meta-analysis of randomized controlled trials (RCTs).

METHODS/MATERIALS

We searched multiple databases for RCTs investigating the impact of the following strategies for the purpose of determining whether or not to defer PCI: fractional flow reserve, instantaneous wave-free ratio, quantitative flow ratio (QFR), and CA. We conducted a network meta-analysis for trial-defined major adverse cardiovascular events (MACE), all-cause death, cardiovascular death, myocardial infarction (MI), target lesion revascularization (TLR), and stent thrombosis. We performed a subgroup analysis for those with acute coronary syndrome (ACS).

RESULTS

Our search identified 12 eligible RCTs including a total of 13,177 patients. QFR-guided PCI was associated with reduced MACE, MI, and TLR compared with CA-guided PCI (relative risk (RR) 0.68; 95 % confidence interval (CI] [0.49 to 0.94], RR 0.58; 95 % CI [0.36 to 0.96], and RR 0.58; 95 % CI [0.38 to 0.91], respectively). There were no significant differences in any pairs for all-cause death, cardiovascular death, or stent thrombosis. QFR was ranked the best in most outcomes. In the subgroup analysis of the ACS cohort, there were no significant differences in MACE between any comparisons.

CONCLUSIONS

QFR was associated with reduced MACE, MI, and TLR compared with CA, and ranked the best in most outcomes. However, this was not applied in the ACS cohort.

Hemodynamic Impairments of Evaluating Symptomatic Intracranial Atherosclerotic Stenosis using Quantitative Flow Ratio on Digital Subtraction Angiography : A Comparison with Computed Tomography Perfusion, MRI and Fractional Flow Reserve

PURPOSE

Cerebral hemodynamics are important for the management of intracranial atherosclerotic stenosis (ICAS). The quantitative flow ratio (QFR) is a novel angiography-derived index for assessing the functional relevance of ICAS without pressure wires and adenosine. Good diagnostic yield with the hyperemic fractional flow reserve (FFR) have been reported, while data on the comparison of QFR to FFR are scarce.

METHODS

In this prospective study 56 patients with anterior circulation symptomatic ICAS who received endovascular treatment were included. The new method of computing QFR from a single angiographic view, i.e., the Murray law-based QFR (μQFR), was applied to the examined vessels. An artificial intelligence algorithm was developed to realize the automatic delineation of vascular contour. Pressure gradients were measured before and after treatment within the lesion vessel using a pressure guidewire and the FFR was calculated.

RESULTS

There was a good correlation between μQFR and FFR. Preoperative FFR predicted DWI watershed infarction (FFR optimal cut-off level: 0.755). Preoperative μQFR predicted DWI watershed infarction (μQFR optimal cut-off level: 0.51). Preoperative FFR predicted CTP hypoperfusion (FFR best predictive value: 0.62). Preoperative μQFR predicted CTP hypoperfusion (μQFR best predictive value: 0.375).

CONCLUSION

The μQFR based on DSA images can be used as an indicator to assess the functional status of the lesion in patients with ICAS.

Contrasting the relationship of serum uric acid/albumin ratio on quantitative flow ratio with other multiple composite parameters in patients with suspected coronary artery disease

OBJECTIVE

The aim of this study was to investigate the association between quantitative coronary flow reserve (CFR) and the blood uric acid/albumin ratio, as well as multiple clinical parameters, in order to assess the severity of coronary artery functional stenosis.

METHODS

This retrospective cross-sectional study included 257 suspected coronary artery disease patients who underwent coronary angiography (CAG) and quantitative flow ratio (QFR) examinations in the Department of Cardiovascular Medicine at the First Affiliated Hospital of Yangtze University in Jingzhou City, China, between September 2022 and March 2023. The study subjects were divided into two groups based on their QFR values: QFR ≤ 0.80 group and QFR > 0.80 group. Correlation of uric acid-to-albumin ratio (UAR), high-density lipoprotein ratio (MHR), systemic immune-inflammation index (SII), Systemic Inflammation Response Index (SIRI), and Aggregate Index of Systemic Inflammation (AISI) with coronary artery QFR was analyzed using univariate and multivariate logistic regression models, considering them as both continuous and binary variables.

RESULTS

The QFR ≤ 0.80 group consisted of 83 patients, while the QFR > 0.80 group included 174 patients. Significant differences were observed between the QFR ≤ 0.80 and QFR > 0.80 groups in the following parameters: UAR (9.19 ± 2.47 vs 7.61 ± 1.91; p < 0.001), MHR (0.46 ± 0.19 vs 0.37 ± 0.16, p < 0.001), SII (674.98 ± 332.30 vs 571.43 ± 255.82; p = 0.006), SIRI (1.53 ± 0.83 vs 1.29 ± 1.10; p = 0.047), and AISI (340.22 ± 242.10 vs 243.97 ± 151.97; p < 0.001). ROC curve analysis revealed an area under the curve of 0.701 (CI: 0.633-0.770; p < 0.001) for UAR. In the univariate analysis, when treated as binary variables, high levels of UAR, MHR, SII, SIRI, and AISI were found to be significantly associated with the risk of QFR ≤ 0.80 (all P < 0.05). However, in the multivariate regression analysis, only high levels of UAR and AISI remained significantly associated with QFR ≤ 0.80 (all P < 0.05). When treated as continuous variables, the univariate analysis indicated that UAR (OR: 1.412, CI: 1.231-1.620, p < 0.001), e^MHR (OR: 1.394, CI: 1.151-1.687, p < 0.001), lnSII (OR: 1.001, CI: 1.000-1.002, p = 0.008), and lnAISI (OR: 2.695, CI: 1.539-4.719, p = 0.001) were significantly associated with QFR ≤ 0.80. In the multivariate analysis, UAR (OR: 1.373, CI: 1.187-1.587, p < 0.001) and AISI (OR: 2.217, CI: 1.309-3.757, p < 0.001) remained significantly associated with QFR ≤ 0.80.

CONCLUSIONS

The results of this study indicate a significant association between UAR and AISI with QFR ≤ 0.80, suggesting its potential role in predicting the extent of functional coronary artery stenosis in patients with CAD. Additionally, AIRI, identified as an inflammatory marker in the complete blood count, was found to exert influence on the severity of coronary artery physiology.

Effect of hemoglobin A1c management levels on coronary physiology evaluated by quantitative flow ratio in patients who underwent percutaneous coronary intervention

AIMS/INTRODUCTION

The coronary physiology and prognosis of patients with different hemoglobin A1c (HbA1c) levels after percutaneous coronary intervention (PCI) are currently unknown. The aim of this study was to assess the effect of different levels of HbA1c control on coronary physiology in patients who underwent PCI for coronary heart disease combined with type 2 diabetes mellitus by quantitative flow ratio (QFR).

MATERIALS AND METHODS

Patients who successfully underwent PCI and completed 1-year coronary angiographic follow up were enrolled, clinical data were collected, and QFR at immediate and 1-year follow up after PCI was retrospectively analyzed. A total of 257 patients (361 vessels) were finally enrolled and divided into the hemoglobin A1c (HbA1c)-compliance group (103 patients, 138 vessels) and non-HbA1c-compliance group (154 patients, 223 vessels) according to the HbA1c cut-off value of 7%. We compared the results of QFR analysis and clinical outcomes between the two groups.

RESULTS

At 1-year follow up after PCI, the QFR was significantly higher (0.94 ± 0.07 vs 0.92 ± 0.10, P = 0.019) and declined less (0.014 ± 0.066 vs 0.033 ± 0.095, P = 0.029) in the HbA1c-compliance group. Meanwhile, the incidence of physiological restenosis was lower in the HbA1c-compliance group (2.9% vs 8.5%, P = 0.034). Additionally, the target vessel revascularization rate was lower in the HbA1c-compliance group (6.8% vs 16.9%, P = 0.018). Furthermore, HbA1c ≥7% (OR 2.113, 95% confidence interval 1.081-4.128, P = 0.029) and QFR decline (OR 2.215, 95% confidence interval 1.147-4.277, P = 0.018) were independent risk factors for target vessel revascularization.

CONCLUSION

Patients with well-controlled HbA1c levels have better coronary physiological benefits and the incidence of adverse clinical outcome events might be reduced.

Quantitative flow ratio computed from invasive coronary angiography as a predictor for cardiac allograft vasculopathy after cardiac transplant

Cardiac allograft vasculopathy (CAV) is a significant determinant of long-term survival in heart transplant recipients. Standard CAV screening typically utilizes invasive coronary angiography (ICA). Quantitative flow ratio (QFR) is a computational method for functional testing of coronary stenosis, and may add diagnostic value to ICA in assessing CAV. Consecutive subjects who received heart transplantation and underwent two separate routine coronary angiograms between January 2013 and April 2016 were enrolled. Coronary angiograms and IVUS were performed per local protocol at 1, 2, 3 and 5 years post-transplant. QFR was calculated offline. CAV was assessed semi-quantitively based on coronary angiogram results. Twenty-two patients were enrolled. Mean time from transplant to first included ICA was 2.1 years. QFR in at least 1 coronary vessel was interpretable in 19/22 (86%) of initial ICA (QFR1). QFR1 correlated well with the CAV score derived from the second ICA (CAV2) with a clustering of CAV at lower QFR values. In a receiver-operating characteristic (ROC) analysis, an optimal QFR threshold of 0.88 yielded 0.94 sensitivity and 0.67 specificity (AUC of 0.79) for at least non-obstructive subsequent CAV. Initial angiographically and intravascular ultrasound derived CAV severity poorly predicted subsequent CAV severity. QFR derived from invasive coronary angiography predicts subsequent development of CAV more accurately than angiography and intravascular ultrasound. This novel method of coronary flow assessment in recipients of heart transplantation may be useful to diagnose and predict subsequent CAV development.

Long-term intracoronary imaging and physiological measurements of bioresorbable scaffolds and untreated atherosclerotic plaques

BACKGROUND

Bioresorbable scaffolds (BRS) provide the prospect of restoring the anatomic and physiologic characteristics of the vascular wall.

OBJECTIVE

This study sought to examine the long-term outcomes of BRS-based coronary intervention in a young population with diffuse and severe coronary atherosclerotic disease (CAD) and to compare the long-term evolution of treated segments versus the natural progression of untreated non-flow limiting stenoses.

METHODS

Observational, single-center cohort study that prospectively included patients that underwent percutaneous coronary intervention with implantation of ABSORB BRS (Abbott Vascular). The clinical endpoint was the incidence of device-oriented composite endpoint (DoCE) up to 5 years follow-up. A subgroup of patients with baseline intracoronary imaging assessment of long lesions and/or multivessel disease underwent elective angiographic (70 patients, 129 lesions) and intracoronary imaging (55 patients, 102 lesions) follow-up. Paired intravascular ultrasound (IVUS) and quantitative flow reserve (QFR) were analyzed.

RESULTS

Between 2012 and 2017, 159 patients (mean age 54.0 ± 11.1) with native CAD were treated with BRS on 247 lesions. Patients were mainly at their first cardiac event, mostly acute coronary syndromes (86.5%). At the median follow-up time of 56 months [41-65], DoCE occurred in 15/159 (9.4%) patients, while non-target vessel-oriented composite endpoint occurred in 16 patients (10.4%). A significant atherosclerotic progression was detected on residual non-flow limiting plaques as per IVUS and QFR assessment, while no significant change was detected in the treated segment.

CONCLUSIONS

Mild-to-moderate asymptomatic CAD progressed significantly at 5-year despite OMT. BRS-treated segments had a less aggressive progression at 5-year despite more severe and symptomatic CAD at baseline.

Prognostic role of discordance between quantitative flow ratio and visual estimation in revascularization guidance

Aims

Revascularization guided by functional severity has presented improved outcomes compared with visual angiographic guidance. Quantitative flow ratio (QFR) is a reliable angiography-based method for functional assessment. We sought to investigate the prognostic value of discordance between QFR and visual estimation in coronary revascularization guidance.

Methods and results

We performed offline QFR analysis on all-comers undergoing coronary angiography. Vessels with calculated QFR were divided into four groups based on the decision to perform or defer percutaneous coronary intervention (PCI) and on the QFR result, i.e.: Group A (PCI-, QFR > 0.8); Group B (PCI+, QFR ≤ 0.8); Group C (PCI+, QFR > 0.8); Group D (PCI-, QFR ≤ 0.8). Patients with at least one vessel falling within the disagreement groups formed the discordance group, whereas the remaining patients formed the concordance group. The primary endpoint was the composite endpoint of cardiovascular death, myocardial infarction, and ischaemia-driven revascularization. Overall, 546 patients were included in the study. Discordance between QFR and visual estimation was found in 26.2% of patients. After a median follow-up period of 2.5 years, the discordance group had a significantly higher rate of the composite outcome (hazard ratio: 3.34, 95% confidence interval 1.99-5.60, P < 0.001). Both disagreement vessel Groups C and D were associated with increased cardiovascular risk compared with agreement Groups A and B.

Conclusion

Discordance between QFR and visual estimation in revascularization guidance was associated with a worse long-term prognosis. Our results highlight the importance of proper patient selection for intervention and the need to avoid improper stent implantations when not dictated by a comprehensive functional assessment.

Impact of Relative Improvement in Quantitative Flow Ratio on Clinical Outcomes After Percutaneous Coronary Intervention - A Subanalysis of the PANDA III Trial

BACKGROUND

The clinical impact of relative improvements in coronary physiology in patients receiving percutaneous coronary intervention (PCI) for coronary artery disease (CAD) remains undetermined.Methods and Results: The quantitative flow ratio (QFR) recovery ratio (QRR) was calculated in 1,424 vessels in the PANDA III trial as (post-PCI QFR-pre-PCI QFR)/(1-pre-PCI QFR). The primary endpoint was the 2-year vessel-oriented composite endpoint (VOCE; a composite of vessel-related cardiac death, vessel-related non-procedural myocardial infarction, and ischemia-driven target vessel revascularization). Study vessels were dichotomously stratified according to the optimal QRR cut-off value. During the 2-year follow-up, 41 (2.9%) VOCEs occurred. Low (<0.86) QRR was associated with significantly higher rates of 2-year VOCEs than high (≥0.86) QRR (6.6% vs. 1.4%; adjusted hazard ratio [aHR] 5.05; 95% confidence interval [CI] 2.53-10.08; P<0.001). Notably, among vessels with satisfactory post-procedural physiological results (post-PCI QFR >0.89), low QRR also conferred an increased risk of 2-year VOCEs (3.7% vs. 1.4%; aHR 3.01; 95% CI 1.30-6.94; P=0.010). Significantly better discriminant and reclassification performance was observed after integrating risk stratification by QRR and post-PCI QFR to clinical risk factors (area under the curve 0.80 vs. 0.71 [P=0.010]; integrated discrimination improvement 0.05 [P<0.001]; net reclassification index 0.64 [P<0.001]).

CONCLUSIONS

Relative improvement of coronary physiology assessed by QRR showed applicability in prognostication. Categorical classification of coronary physiology could provide information for risk stratification of CAD patients.

Effects of percutaneous coronary intervention and diabetes mellitus on short- and long-term prognosis assessed by the three-vessel quantitative flow ratio

AIMS

We aimed to investigate the impact of percutaneous coronary intervention (PCI) and diabetes mellitus (DM) on short- and long-term prognosis in patients with coronary artery disease using three-vessel quantitative flow ratio (3 V-QFR) assessment.

METHODS

A retrospective analysis of 2440 vessels in 1181 patients who underwent PCI was performed. The patients were categorized according to the presence or absence of DM and the median 3 V-QFR. The primary outcome was the occurrence of major adverse cardiac events (MACE), defined as a combination of cardiovascular death, myocardial infarction, and ischemia-driven revascularization, over a 5-year period.

RESULTS

The pre-PCI and post-PCI 3 V-QFR values for the entire population were 2.37 (2.04-2.56) and 2.94 (2.82-3.00), respectively. Landmark analysis showed that the incidence of MACE was comparable among all groups within the first year (log-rank p = 0.088). Over the course of 2 years, the incidence of MACE was higher in both groups with a post-PCI 3 V-QFR < 2.94 (log-rank p < 0.001). However, from 2 to 5 years, patients with DM had higher rates of MACE (log-rank p = 0.013).

CONCLUSIONS

In the short term, a low post-PCI 3 V-QFR is a predictor of high risk for MACE. However, in the long term, DM emerges as the dominant risk factor.

Diagnostic performance of quantitative flow ratio in non-ST elevation acute coronary syndromes in comparison to non-hyperemic pressure ratios: a prospective study

Quantitative flow ratio (QFR) is a new angiography-based coronary physiology tool aimed to evaluate functional relevance of intermediate coronary lesions. Aim of the study is to assess diagnostic performance of QFR in patients with non-ST-elevation acute coronary syndrome (NSTE-ACS) in comparison to currently used non-hyperaemic pressure ratios (NHPRs). In this prospective, single-centre study, coronary physiology of intermediate coronary stenoses of non-culprit vessels in patients presenting with NSTE-ACS was evaluated using NHPRs (iFR, DFR or RFR). Subsequently, QFR was computed offline by a QFR analyst blinded to the NHPR results. Diagnostic performance of QFR was assessed in comparison to NHPRs as reference standard. A total of 60 vessels with intermediate coronary stenoses was investigated. The NHPRs were used as follows: RFR 38%, DFR 47% and iFR 15% of the cases. The NHPR result was positive, showing significant lesion, in 19 cases. A significant correlation was found between NHPR and QFR (r = 0.84, p < 0.001). Classification agreement of the two methods (95%) and diagnostic performance of QFR in comparison to NHPR (AUC: 0.962 [0.914-1.00]) were both high. Sensitivity, specificity, positive and negative predictive value of QFR in comparison to NHPR were 84.2%, 100%, 100% and 93.2% respectively. QFR has high diagnostic performance in detecting functionally significant lesions of non-culprit arteries in patients with NSTE-ACS and multivessel disease. Due to its high negative predictive value, it can be used to safely avoid unnecessary invasive physiological assessment of these lesions.

Left main bifurcation stenting: impact of residual ischaemia on cardiovascular mortality

AIMS

The present study sought to determine the rate and prognostic implications of post-procedural physiologically significant residual ischemia according to Murray law-based quantitative flow ratio (μQFR) after left main (LM) bifurcation percutaneous coronary intervention (PCI).

METHODS AND RESULTS

Consecutive patients undergoing LM bifurcation stenting at a large tertiary care center between January 2014 and December 2016 with available post-PCI μQFR were included. Physiologically significant residual ischemia was defined by post-PCI μQFR values ≤0.80 in the left anterior descending (LAD) or left circumflex artery (LCX). The primary outcome was 3-year cardiovascular death. The major secondary outcome was 3-year bifurcation-oriented composite endpoint (BOCE). Among 1170 included patients with analyzable post-PCI μQFR, 155 (13.2%) had residual ischemia in either LAD or LCX. Patients with vs. those without residual ischemia had a higher risk of 3-year cardiovascular mortality [5.4% vs. 1.3%; adjusted hazard ratio (HR) 3.20, 95% confidence interval (CI): 1.16-8.80]. The 3-year risk of BOCE was significantly higher in the residual ischemia group (17.8% vs. 5.8%; adjusted HR 2.79, 95% CI: 1.68-4.64), driven by higher incidence of the composite of cardiovascular death and target bifurcation-related myocardial infarction (14.0% vs. 3.3%; adjusted HR 4.06, 95% CI: 2.22-7.42). A significant, inverse association was observed between continuous post-PCI μQFR and the risk of clinical outcomes (per 0.1 μQFR decrease, HR of cardiovascular death 1.27, 95% CI: 1.00-1.62; HR of BOCE 1.29, 95% CI: 1.14-1.47).

CONCLUSION

After angiographically successful LM bifurcation PCI, residual ischemia assessed by μQFR was identified in 13.2% of patients and was associated with higher risk of 3-year cardiovascular death, indicating the superior prognostic value of post-PCI physiological assessment.

Long-term prognostic value of quantitative-flow-ratio-concordant revascularization in stable coronary artery disease

OBJECTIVES

Confirming the prognostic value of global QFR and evaluating the long-term prognosis of QFR-concordant therapy in stable coronary artery disease.

BACKGROUND

Wire-based functional evaluation of coronary disease is linked to patient's prognosis. Quantitative Flow Ratio (QFR) is a newer index of computational physiology, linked to clinical outcomes and prognosis at 1 year follow-up. Long-term prognosis of QFR-concordant revascularization in stable coronary artery disease is however unknown hitherto.

METHODS

Consecutive patients with stable coronary disease undergoing coronary angiography were included. Centralized and blinded QFR analysis of three coronary territories was performed. Three vessel QFR (3vQFR) was defined as the sum of the basal QFR of each coronary territory. QFR-concordant revascularization was met if all significant lesions (QFR ≤ 0.80) were revascularized and all non-significant lesions (QFR > 0.80) were not; otherwise, the case was defined as QFR-discordant revascularization. Patient-oriented composite end-point (POCE) of cardiac death, myocardial infarction and unscheduled revascularization was the primary endpoint.

RESULTS

A total of 803 patients from six high-volume centers were included. Canadian Cardiovascular Society (CCS) class II angina was the most frequent (48.9%) clinical presentation. Median of follow-up was 68.8 months. 3vQFR was an independent predictor of POCE (HR 1.79 CI95% 1.01-3.18), with 2.75 as optimal cut-off value, irrespective of the therapy received. QFR-discordant revascularization (QFR+/Revascularization- or QFR-/Revascularization+) was an independent predictor of POCE in multivariate analysis (HR 1.65, CI 95% 1.03-2.64).

CONCLUSION

Global burden of epicardial coronary atherosclerosis, as evaluated by 3vQFR, as well as QFR-discordant therapy are independent predictors of adverse clinical outcome at long-term follow-up in stable coronary artery disease.

Quantitative Flow Ratio-Derived Index of Microcirculatory Resistance as a Novel Tool to Identify Microcirculatory Function in Patients with Ischemia and No Obstructive Coronary Artery Disease

BACKGROUND

Coronary microvascular disease (CMVD) is associated with adverse cardiovascular outcomes. However, there is no reliable and noninvasive quantitative diagnostic method available for CMVD. The use of a pressure wire to measure the index of microcirculatory resistance (IMR) is possible, but it has inevitable practical restrictions. We hypothesized that computation of the quantitative flow ratio could be used to predict CMVD with symptoms of ischemia and no obstructive coronary artery disease (INOCA).

METHODS

We retrospectively assessed the diagnostic efficiency of the quantitative flow ratio-derived index of microcirculatory resistance (QMR) in 103 vessels from 66 patients and compared it with invasive IMR using the thermodilution technique.

RESULTS

Patients were divided into the CMVD group (41/66, 62.1%) and non-CMVD group (25/66, 37.9%). Pressure wire IMR measurements were made in 103 coronary vessels, including 44 left descending arteries, 18 left circumflex arteries, and 41 right coronary arteries. ROC curve analysis showed a good diagnostic performance of QMR for all arteries (area under the curve = 0.820, 95% confidence interval 0.736-0.904, p < 0.001) in predicting microcirculatory function. The optimal cut-off for QMR to predict microcirculatory function was 266 (sensitivity: 82.9%, specificity: 72.6%, and diagnostic accuracy: 76.7%).

CONCLUSION

QMR is a promising tool for the assessment of coronary microcirculation. The assessment of the IMR without the use of a pressure wire may enable more rapid, convenient, and cost-effective assessment of coronary microvascular function.

Impact of quantitative flow ratio on graft function in patients undergoing coronary artery bypass grafting

Recent studies showed that preoperative functional assessment with fractional flow reserve (FFR) could predict a long-term patency of arterial bypass grafts in patients with coronary artery bypass grafting (CABG). Quantitative flow ratio (QFR) is a novel angiography-based approach to estimate FFR. This study aimed to investigate whether preoperative QFR could discriminate arterial bypass function at 1 year after surgery. The PRIDE-METAL registry was a prospective, multicenter observational study that enrolled 54 patients with multivessel coronary artery disease. By protocol, left coronary stenoses were revascularized by CABG with arterial grafts, whereas right coronary stenoses were treated with coronary stenting. Follow-up angiography at 1 year after surgery was scheduled to assess arterial graft patency. QFR was performed using index angiography by certified analysts, blinded to bypass graft function. The primary end point of this sub-study was the discriminative ability of QFR for arterial graft function, as assessed by receiver-operating characteristic curve. Among 54 patients enrolled in the PRIDE-METAL registry, index and follow-up angiography was available in 41 patients with 97 anastomoses. QFR were analyzed in 35 patients (71 anastomoses) with an analyzability of 85.5% (71/83). Five bypass grafts were found to be non-functional at 1 year. The diagnostic performance of QFR was substantial (area under the curve: 0.89; 95% confidence interval: 0.83 to 0.96) with an optimal cutoff of 0.76 to predict functionality of bypass grafts. Preoperative QFR is highly discriminative for predicting postoperative arterial graft function.Trial registration: Clinical.gov reference: NCT02894255.

Development and validation of a simple model to predict functionally significant coronary artery disease in Chinese populations: A two-center retrospective study

Objectives

This study sought to derive and validate a simple model combining traditional clinical risk factors with biomarkers and imaging indicators easily obtained from routine preoperative examinations to predict functionally significant coronary artery disease (CAD) in Chinese populations.

Methods

We developed five models from a derivation cohort of 320 patients retrospective collected. In the derivation cohort, we assessed each model discrimination using the area under the receiver operating characteristic curve (AUC), reclassification using the integrated discrimination improvement (IDI) and net reclassification improvement (NRI), calibration using the Hosmer-Lemeshow test, and clinical benefit using decision curve analysis (DCA) to derive the optimal model. The optimal model was internally validated by bootstrapping, and external validation was performed in another cohort including 96 patients.

Results

The optimal model including 5 predictors (age, sex, hyperlipidemia, hs-cTnI and LVEF) achieved an AUC of 0.807 with positive NRI and IDI in the derivation cohort. Moreover, the Hosmer-Lemeshow test showed a good fit, and the DCA demonstrated good clinical net benefit. The C-statistic calculated by bootstrapping internal validation was 0.798, and the calibration curve showed adequate calibration (Brier score = 0.179). In the external validation cohort, the optimal model performance was acceptable (AUC = 0.704; Brier score = 0.20). Finally, a nomogram based on this model was constructed to facilitate its use in clinical practice.

Conclusions

A simple model combined clinical risk factors with hs-cTnI and LVEF improving the prediction of functionally significant CAD in Chinese populations. This attractive model may be a choice for clinicians to risk stratification for CAD.

Fast Computational Approaches to Derive Fractional Pressure Ratio in Patients with Extracranial or Intracranial Symptomatic Stenosis

OBJECTIVE

We aimed to evaluate the performance of fast and straightforward Murray law-based quantitative flow ratio (μQFR) computation in cerebrovascular stenosis.

METHODS

A total of 30 patients with symptomatic stenosis of 50%-70% luminal stenosis and underwent fractional pressure ratio (FPR) assessment at our hospital were included in the present study. μQFR was applied to the interrogated vessel. An artificial intelligence algorithm was proposed for automatic delineation of lumen contours of cerebrovascular stenosis. We used invasive FPRs as a reference standard. Pearson's correlation coefficient (r) was used to assess the correlation strength between the μQFR and FPR, and Bland-Altman plots were used to evaluate the agreement between the μQFR and FPR. An analysis of the receiver operating characteristic was used to evaluate the performance of μQFR.

RESULTS

Our results displayed a strong positive correlations (r = 0.92; P < 0.001) between the μQFR and pressure wire FPR. Excellent agreement was observed between the μQFR and FPR with a mean difference of 0.01 ± 0.08 (range, -0.16 to 0.14; P = 0.263). The overall accuracy for identifying an FPR of ≤0.7 was 92% (95% confidence interval [CI], 85%-100%). The area under the receiver operating characteristic curve was higher for the μQFR (0.92; 95% CI, 0.81-0.98) than for diameter stenosis (0.88; 95% CI, 0.75-0.95). The positive likelihood ratio was 3.9 for the μQFR with a negative likelihood ratio of 0.

CONCLUSIONS

The μQFR computation has a strong correlation and agrees with the FPR calculated from the pressure wire. Therefore, the μQFR might provide an essential therapeutic aid for patients with symptomatic stenosis.

Angio-based coronary functional assessment predicts 30-day new-onset heart failure after acute myocardial infarction

AIMS

Suboptimal perfusion leading to heart failure (HF) often occurs after ST-segment elevation myocardial infarction (STEMI), despite restoration of epicardial coronary flow in primary percutaneous coronary intervention (PPCI) era. We determined the clinical implications of angio-based coronary functional assessment in evaluation of suboptimal perfusion and further outcomes among STEMI patients after successful PPCI.

METHODS AND RESULTS

In this study, STEMI patients in the Chinese STEMI PPCI registry trial (NCT04996901) who achieved post-PPCI thrombolysis in myocardial infarction grade 3 flow were retrospectively screened. Post-procedural quantitative flow ratio (QFR), angio-based microvascular resistance (AMR), and coronary flow velocity (CFV) of the infarct-related artery were calculated. QFR and AMR measure epicardial stenosis severity and microvascular resistance, respectively. QFR+ was defined as QFR < 0.90 while QFR- was QFR ≥ 0.90. AMR+ was defined as AMR ≥ 250 mmHg*s/m while AMR- was AMR < 250 mmHg*s/m. The primary outcome was 30-day new-onset HF. The Kaplan-Meier curves were used to establish the associations between QFR, AMR, CFV, and HF incidences. The relationship between CFV and combined QFR and AMR indices was further assessed. Independent predictors were determined using Cox regression analysis. The receiver-operating characteristic curve was used to assess discriminant ability to predict HF. A total of 942 patients (mean age was 57.8 ± 11.7 years and 84.6% were men) were enrolled. Among them, 129 patients had new-onset HF episodes. Patients in the QFR-/AMR- group had a low risk of HF compared with those in the QFR+/AMR+ group (10.5% vs. 27.3%, P = 0.027). A higher CFV ≥ 17.4 cm/s was associated with low HF incidences as compared with CFV < 17.4 cm/s (10.3% vs. 16.8%, P = 0.005), whereas isolated QFR or AMR did not reveal any marked differences in HF incidences (P = 0.150 and 0.079, respectively). The highest and lowest medians of CFV were observed in the QFR-/AMR- and QFR+/AMR+ groups, respectively. CFV correlated well with the QFR/AMR ratio (adjusted R2  = 1, P < 0.001) and post-PPCI CFV was found to be an independent predictor of post-STEMI HF (adjusted hazard ratio: 0.61, 95% confidence interval: 0.41-0.90, P = 0.012). The area under curve estimate of the multivariable regression model was 0.749.

CONCLUSIONS

CFV is an integrated coronary physiological assessment approach that incorporates epicardial and microcirculatory contributions. Patients with post-PPCI CFV < 17.4 cm/s were strongly associated with a high risk for post-STEMI HF, even achieving thrombolysis in myocardial infarction grade 3 flow. The immediate angio-based coronary functional assessment is a feasible tool for evaluating suboptimal perfusion and risk stratification.

Effects of remote ischemic preconditioning on coronary blood flow and microcirculation

This study aimed to determine the effect of short-term remote ischemic preconditioning (RIPC) on coronary blood flow and microcirculation function using the quantitative flow ratio (QFR) and index of microcirculatory resistance (IMR). We randomly divided 129 patients undergoing coronary angiography (CAG) into RIPC and control groups. Following the first CAG, we randomly divided the patients further into the unilateral upper limb and lower limb groups for four cycles of ischemia/reperfusion circulation; subsequently, we performed the second CAG. During each CAG, contrast-flow QFR (cQFR), fixed-flow QFR (fQFR), and IMR (in patients with cardiac syndrome X) were calculated and compared. We measured 253 coronary arteries in 129 patients. Compared to the control group, the average cQFR of the RIPC group increased significantly after RIPC. Additionally, 23 patients with cardiac syndrome X (IMR > 30) were included in this study. Compared to the control group, IMR and the difference between cQFR and fQFR (cQFR-fQFR) both decreased significantly after receiving RIPC. The application of RIPC can increase coronary blood flow and improve coronary microcirculation function.

Predictors of long-term adverse outcomes after successful chronic total occlusion intervention: physiology or morphology?

BACKGROUND

Quantitative flow ratio (QFR) and target-vessel SYNTAX score (tvSS) are novel indices used to assess lesion physiology and morphology in percutaneous coronary intervention (PCI). Their prognostic implication after successful recanalization of coronary chronic total occlusion (CTO) is unknown.

OBJECTIVES

To investigate the prognostic value of QFR measured immediately after successful CTO-recanalization in predicting vessel-oriented adverse events, and to compare it with the pre-procedural morphological tvSS.

METHODS

QFR was measured offline after successful CTO-PCIs in a single center. We grouped the patients according to a cut-off value of post-PCI QFR (0.91). The primary outcome was target-vessel failure (TVF) at 2 years.

RESULTS

Among 470 CTO lesions performed during the study period, 324 were eligible for QFR analysis (258 with QFR ≥ 0.91 and 66 with QFR < 0.91). The mean age of the study population was 68.3 ± 10.7 years. The low QFR group had a lower left ventricular ejection fraction (45.8 ± 13.9% vs. 49.8 ± 12.4%, p = 0.025) and a higher rate of atrial fibrillation (19.7% vs. 11.2%, p = 0.020). The mean tvSS was 12.8 ± 4.8, and it showed no significant difference in both groups (13.6 ± 5.1 vs. 12.6 ± 4.6, p = 0.122). Patients with low post-CTO QFR had a trend to develop more TVF at 2 years (21.2% vs. 12.4%, HR 1.74; 95% CI 0.93-3.25, p = 0.086). Low post-CTO QFR failed to predict 2-year TVF (aHR 1.67; 95% CI 0.85-3.29, p = 0.136), while pre-procedural tvSS was an independent predictor for 2-year TVF (aHR 1.06; 95% CI 1.01-1.13, p = 0.030).

CONCLUSION

We found a limited prognostic value of immediate physiological assessment using QFR after successful CTO intervention. Pre-procedure morphological characteristics of CTO lesions using tvSS can play a role in predicting long-term adverse events.

Rationale and design of the iCORONARY trial: improving the cost-effectiveness of coronary artery disease diagnosis

BACKGROUND

In patients with stable coronary artery disease (CAD), revascularisation decisions are based mainly on the visual grading of the severity of coronary stenosis on invasive coronary angiography (ICA). However, invasive fractional flow reserve (FFR) is the current standard to determine the haemodynamic significance of coronary stenosis. Non-invasive and less-invasive imaging techniques such as computed-tomography-derived FFR (FFR-CT) and angiography-derived FFR (QFR) combine both anatomical and functional information in complex algorithms to calculate FFR.

TRIAL DESIGN

The iCORONARY trial is a prospective, multicentre, non-inferiority randomised controlled trial (RCT) with a blinded endpoint evaluation. It investigates the costs, effects and outcomes of different diagnostic strategies to evaluate the presence of CAD and the need for revascularisation in patients with stable angina pectoris who undergo coronary computed tomography angiography. Those with a Coronary Artery Disease-Reporting and Data System (CAD-RADS) score between 0-2 and 5 will be included in a prospective registry, whereas patients with CAD-RADS 3 or 4A will be enrolled in the RCT. The RCT consists of three randomised groups: (1) FFR-CT-guided strategy, (2) QFR-guided strategy or (3) standard of care including ICA and invasive pressure measurements for all intermediate stenoses. The primary endpoint will be the occurrence of major adverse cardiac events (death, myocardial infarction and repeat revascularisation) at 1 year.

CLINICALTRIALS

gov-identifier: NCT04939207.

CONCLUSION

The iCORONARY trial will assess whether a strategy of FFR-CT or QFR is non-inferior to invasive angiography to guide the need for revascularisation in patients with stable CAD. Non-inferiority to the standard of care implies that these techniques are attractive, less-invasive alternatives to current diagnostic pathways.

angiography-only guided PCI in STEMI patients: one-year cardiovascular outcomes

BACKGROUND

Coronary physiology-guided PCIs are recommended worldwide. However, invasive coronary physiology methods prolong the procedure, create additional risks for the patients, and prolong the fluoroscopy time for an interventional cardiologist. Otherwise, there is a noninvasive coronary physiology evaluation method, QFR, that can be safely used even in STEMI patients.

METHODS

A total of 198 patients admitted with STEMI and at least one intermediate (35-75%) diameter stenosis other than the culprit artery between July 2020 and June 2021 were prospectively included in this single-center study. All patients were randomized into one of two groups (1 - QFR-guided PCI; 2 - visual-estimation-only guided PCI). A 12-month follow-up with echocardiography, exercise stress test, and quality of life evaluation was performed in all included patients. For the QOF evaluation, the Seattle Angina Score Questionnaire was chosen. Statistical analysis was performed using the Kolmogorov-Smirnov test, Student's t-test, Mann-Whitney U test, Pearson's chi-squared test and Kaplan-Meier estimator.

RESULTS

Ninety-eight (49.5%) patients were randomized to the first group, and 100 (50.5%) patients were included in the second group. Statistically, significantly more patients had a medical history of dyslipidemia (98 vs. 91, p = 0.002) and slightly better left ventricular ejection fraction (42.21 ± 7.88 vs. 39.45 ± 9.62, p = 0.045) in the QFR group. Six fewer patients required non-culprit artery revascularization within the 12-month FU in the QFR group (1.02% vs. 6%, p = 0.047). Survival analysis proved that patients in the Angio group had a more than 6-fold greater risk for death within a 12-month period after MI (OR 6.23, 95% CI 2.20-17.87, p = 0.006), with the highest mortality risk within the first two months after initial treatment.

CONCLUSION

Using QFR in non-culprit lesions in patients with ST-elevation myocardial infarction reduces mortality and revascularization at the 12-month follow-up and improves the quality of life of the patient.

TRIAL REGISTRATION

The study was approved by the Regional Bioethical Committee and conducted under the principles of the Helsinki Declaration and local laws and regulations.

Anatomical and Functional Discrepancy in Diabetic Patients With Intermediate Coronary Lesions - An Intravascular Ultrasound and Quantitative Flow Ratio Study

BACKGROUND

Data regarding the performance of computational fractional flow reserve in patients with diabetes mellitus (DM) remain scarce. This study sought to explore the impact of DM on quantitative flow ratio (QFR) and its association with intravascular ultrasound (IVUS)-derived anatomical references.Methods and Results: IVUS and QFR were retrospectively analyzed in 237 non-diabetic and 93 diabetic patients with 250 and 102 intermediate lesions, respectively. Diabetics were further categorized based on adequate (HbA1c <7.0%: 47 patients with 53 lesions) or poor (HbA1c ≥7.0%: 46 patients with 49 lesions) glycemic control. Lesions with QFR ≤0.8 or minimum lumen area (MLA) ≤4.0 mm²and plaque burden (PB, %) ≥70 were considered functionally or anatomically significant, respectively. PB increased, and MLA decreased stepwise across non-diabetics, diabetics with adequate glycemic control and those with poor glycemic control. In contrast, QFR was similar among the 3 groups. PB correlated significantly with the QFR for lesions in non-diabetics, but not for lesions in diabetics. DM was independently correlated with the functionally non-significant lesions (QFR >0.8) with high-risk IVUS features (MLA ≤4.0 mm²and PB ≥70; OR 2.053, 95% CI: 1.137-3.707, P=0.017). When considering the effect of glycemic control, HbA1c was an independent predictor of anatomical-functional discordance (OR 1.347, 95% CI: 1.089-1.667, P=0.006).

CONCLUSIONS

Anatomical-functional discordance of intermediate coronary lesions assessed by IVUS and QFR is exacerbated in patients with diabetes, especially when glycemia is poorly controlled.

Angiography-derived index of microvascular resistance in takotsubo syndrome

Coronary microvascular dysfunction (CMD) has been proposed as a key driver in the etiopathogenesis of Takotsubo syndrome (TTS), likely related to an "adrenergic storm" upon a susceptible microvascular circulation. The aim of our manuscript was to assess CMD in patients with TTS through the computation of the angiography-derived index of microcirculatory resistance (IMR) and its correlation with clinical presentation. Coronary angiograms of 41 consecutive TTS patients were retrospectively analyzed to derive angiography-based indices of CMD. Three indices (NH-IMRangio, AngioIMR and A-IMR) were calculated based on quantitative flow ratio. CMD was defined as an IMRangio value ≥ 25 units. The correlation between CMD and clinical presentation was then assessed. Median age was 76 years, 85.7% were women and mean left ventricular ejection fraction (LVEF) at first echocardiogram was 41.2%. Angiography-derived IMR was higher in left anterior descending artery (LAD) than circumflex and right coronary artery with either NH-IMRangio (53.9 ± 19.8 vs 35.8 ± 15.4 vs 40.8 ± 18.5, p-value < 0.001), AngioIMR (47.2 ± 17.3 vs 31.8 ± 12.2 vs 37.3 ± 13.7, p-value < 0.001) or A-IMR (52.7 ± 19 vs 36.1 ± 14.1 vs 41.8 ± 16.1, p-value < 0.001). All patients presented CMD with angiography-derived IMR ≥ 25 in at least one territory with each formula. Angiography-derived IMR in LAD territory was significantly higher in patients presenting with LVEF impairment (≤ 40%) than in those with preserved ventricular global function (NH-IMRangio: 59.3 ± 18.1 vs 46.3 ± 16.0 p-value = 0.030; AngioIMR: 52.9 ± 17.8 vs 41.4 ± 14.2, p-value = 0.037; A-IMR: 59.2 ± 18.6 vs 46.3 ± 17.0, p-value = 0.035). CMD assessed with angiography-derived IMR is a common finding in TTS and it is inversely correlated with LV function. The available formulas have a substantial superimposable diagnostic performance in assessing coronary microvascular function.

Diagnostic comparison of automatic and manual TIMI frame-counting-generated quantitative flow ratio (QFR) values

Quantitative flow ratio (QFR) is a computational measurement of FFR (fractional flow reserve), calculated from coronary angiography. Latest QFR software automates TIMI frame counting (TFC), which occurs during the flow step of QFR analyses, making the analysis faster and more reproducible. The objective is to determine the diagnostic performance of QFR values obtained from analyses using automatic TFC compared to those obtained from analyses using manual TFC. This was a single-arm clinical trial that used the prospective analysis of the coronary angiographic image series of 97 patients who underwent evaluation of stable coronary artery disease with FFR/iFR at MedStar Washington Hospital Center in Washington, DC, USA. Automatic and manual TFC QFR values were obtained from the analyses of each of the 97 patients' image series, with manual TFC QFR values as the current gold standard for comparison. The diagnostic performance of automatic TFC QFR values was measured as follows: sensitivity was 0.87 (95% CI 0.66-0.97) and specificity was 1.00 (95% CI 0.9514-1.00), positive predictive value (PPV) was 1.00 (95%CI 1.00-1.00), while the NPV was 0.96 (95% CI 0.96-0.99). Overall accuracy was 96.91% (95% CI 91.23%-99.36%). The agreement as illustrated by the Bland-Altman plot shows a bias of 0.0023 (SD 0.0208) and narrow limits of agreement (LOA): Upper LOA 0.0573 and Lower LOA - 0.0528. The area under curve (AUC) was 0.996. QFR values generated from automatic TFC are comparable to those generated from manual TFC in diagnostic capability. The most recent software update produces values equivalent to those of the previous manual option, and can therefore be used interchangeably.

Quantitative flow ratio for evaluation of borderline coronary lesions in patients with severe aortic stenosis

INTRODUCTION AND OBJECTIVES

Quantitative flow ratio (QFR) is a novel noninvasive method for evaluating coronary physiology. However, data on the QFR in patients with aortic stenosis (AS) and coronary artery disease are scarce. Thus, we compared the diagnostic performance of the QFR with that of the resting distal to aortic coronary pressure (Pd/Pa) ratio, fractional flow reserve (FFR), and instantaneous wave-free ratio (iFR), as well as angiographic indices.

METHODS

A total of 221 AS patients with 416 vessels undergoing FFR/iFR measurements were enrolled in the study.

RESULTS

The mean percent diameter stenosis (%DS) was 58.6%±13.4% and the mean Pd/Pa ratio, FFR, iFR, and QFR were 0.95±0.03, 0.85±0.07, 0.90±0.04, and 0.84±0.07, respectively. A FFR ≤ 0.80 was noted in 26.0% of interrogated vessels, as well as an iFR ≤ 0.89 in 33.2% and QFR ≤ 0.80 in 31.7%. The QFR had better agreement with FFR (intraclass correlation coefficient [ICC], 0.96; 95% confidence interval [95%CI], 0.95-0.96) than with the iFR (ICC, 0.79; 95%CI, 0.75-0.82) and Pd/Pa ratio (ICC, 0.52; 95%CI, 0.44-0.58). In addition, the QFR showed better diagnostic accuracy (98.6% vs 94.2%; P <.001) and discriminant function (area under the curve=0.996 vs 0.988; P <.001) when the iFR was used as the reference instead of FFR.

CONCLUSIONS

In patients with AS, the QFR has good agreement with both FFR and iFR. However, the agreement appears to be even better when the iFR is used as the reference, presumably due to the complex nature of the coronary physiology in the assessment of coronary artery disease in patients with severe AS.

Angiography-Based Fractional Flow Reserve: State of the Art

Purpose of Review

Three-dimensional quantitative coronary angiography-based methods of fractional flow reserve (FFR) derivation have emerged as an appealing alternative to conventional pressure-wire-based physiological lesion assessment and have the potential to further extend the use of physiology in general. Here, we summarize the current evidence related to angiography-based FFR and perspectives on future developments.

Recent Findings

Growing evidence suggests good diagnostic performance of angiography-based FFR measurements, both in chronic and acute coronary syndromes, as well as in specific lesion subsets, such as long and calcified lesions, left main coronary stenosis, and bifurcations. More recently, promising results on the superiority of angiography-based FFR as compared to angiography-guided PCI have been published.

Summary

Currently available angiography -FFR indices proved to be an excellent alternative to invasive pressure wire-based FFR. Dedicated prospective outcome data comparing these indices to routine guideline recommended PCI including the use of FFR are eagerly awaited.

Effects of diabetes mellitus on post-intervention coronary physiological assessment derived by quantitative flow ratio in patients with coronary artery disease underwent percutaneous coronary intervention

AIMS

To compare the prognostic implication of post-percutaneous coronary intervention (PCI) quantitative flow ratio (QFR) assessment in patients with and without diabetes enrolled in the all-comers, multicenter, randomized controlled PANDA III trial.

METHODS

All treated vessels in PANDA III trial were retrospectively assessed for post-PCI QFR. Vessels with available post-PCI QFR were further stratified into DM and non-DM cohorts, and prognostic performance of post-PCI QFR was compared in 2 cohorts. The primary outcome was 2-year vessel-oriented composite endpoint (VOCE), defined as composite of vessel-related cardiac death, vessel-related non-procedural myocardial infarction, and ischemia-driven target vessel revascularization.

RESULTS

Of 2,989 treated vessels, 2,227 (74.5%) with available post-PCI QFR were included, while 548 were presence of DM and 1,679 were not. The performance of post-PCI QFR to predict 2-year VOCE were moderate in both DM (area under the curve [AUC] 0.77, 95% confidence interval [CI]: 0.68 to 0.87) and non-DM cohorts (AUC 0.74, 95% CI: 0.67 to 0.82), while between-cohorts AUC difference was not significant (ΔAUC 0.03, P = 0.65). After multivariate adjustment, vessels with suboptimal post-PCI QFR results (≤0.92) were associated with higher risk of 2-year VOCE in both DM (adjusted HR 6.24, 95% CI: 2.40 to 16.2) and non-DM cohorts (adjusted HR 5.92, 95% CI: 3.28 to 10.7) without significant interaction (P for interaction 0.91).

CONCLUSIONS

This study, the first to directly compare clinical value of post-PCI QFR assessments in patients with and without DM, showed that a higher post-PCI QFR value was associated with improved long-term prognosis regardless of the presence of DM. Clinical Trial Registration Information URL: https://www.

CLINICALTRIALS

gov; Unique identifier: NCT02017275.

Impact of diabetes on coronary physiology evaluated by quantitative flow ratio in patients who underwent percutaneous coronary intervention

Aims/Introduction

There are mixed opinions on the influence of diabetes on the prognosis of patients receiving percutaneous coronary intervention (PCI). Therefore, in this study, the quantitative flow ratio (QFR), an emerging technology of functional evaluation, was used to explore the impact of diabetes on coronary physiology in patients who underwent PCI.

Materials and Methods

Patients who underwent successful PCI and a 1‐year angiographic follow up were retrospectively screened and analyzed by the QFR. Based on the presence or absence of diabetes, 677 enrolled patients (794 vessels) were classified into a diabetes group (211 patients, 261 vessels) and a non‐diabetes group (466 patients, 533 vessels). The results of QFR analysis and clinical outcomes were compared between the two groups.

Results

The two groups reached a similar level of post‐PCI QFR (0.95 ± 0.09 vs 0.96 ± 0.06, P = 0.292). However, at the 1‐year follow up, the QFR was lower (0.93 ± 0.11 vs 0.96 ± 0.07, P < 0.001), and the degree of QFR decline was more obvious (−0.024 ± 0.090 vs −0.008 ± 0.070, P = 0.023) in the diabetes group. Additionally, diabetes was independently associated with functional restenosis (odds ratio 2.164, 95% confidence interval 1.210–3.870, P = 0.009) and target vessel failure (odds ratio 2.654, 95% confidence interval 1.405–5.012, P = 0.003).

Conclusion

As evaluated by the QFR, patients with diabetes received less coronary physiological benefit from PCI, which was consistent with their clinical outcomes.

Diagnostic agreement of quantitative flow ratio with fractional flow reserve in a Latin-American population

Quantitative flow ratio (QFR) is a recently proposed angiographic index that allows to assess the pressure loss in coronary arteries in a similar fashion as the fractional flow reserve (FFR). The purpose of this study was to evaluate the diagnostic performance of QFR as compared to FFR, in a Latin-American population of patients with suspected ischaemic heart disease. QFR was retrospectively derived from coronary angiograms. The association, diagnostic performance, and continuous agreement of fixed-flow QFR (fQFR) and contrast-flow QFR (cQFR) with FFR was assessed by continuous and dichotomous methods. 90 vessels form 66 patients were finally included. The study comprised coronary stenoses of intermediate severity, both angiographically (diameter stenosis: 46.6 ± 12.8%) and physiologically [median FFR = 0.83 (quartile 1-3, 0.76-0.89)]. The correlation of FFR with both fQFR [ρ = 0.841, (95% CI 0.767 to 0.893), p < 0.001] and cQFR [ρ = 0.833, (95% CI 0.755 to 0.887), p < 0.001] was strong. The diagnostic performance of cQFR was good [area under the ROC curve of 0.92 (95% CI 0.86 to 0.97, p < 0.001)], with 0.80 as the optimal cQFR cut-off against FFR ≤ 0.80. This 0.80 cQFR cut-off classified correctly 83.3% of total stenoses, with a sensitivity of 85.2% and specificity of 80.6%. QFR was strongly associated with FFR and exhibited a high diagnostic performance in this Latin-American population.

One-year performance of biorestorative polymeric coronary bypass grafts in an ovine model: correlation between early biomechanics and late serial Quantitative Flow Ratio

OBJECTIVES

This study aimed to investigate the impact of mechanical factors at baseline on the patency of a restorative conduit for coronary bypass grafts in an ovine model at serial follow-up up to 1 year.

METHODS

The analyses of 4 mechanical factors [i.e. bending angle, superficial wall strain and minimum and maximum endothelial shear stress (ESS)] were performed in 3D graft models reconstructed on baseline (1-month) angiograms frame by frame by a core laboratory blinded for the late follow-up. The late patency was documented by Quantitative Flow Ratio (QFR®) that reflects the physiological status of the graft. The correlation between 4 mechanical factors and segmental QFR (△QFR) were analysed on 10 equal-length segments of each graft.

RESULTS

A total of 69 graft geometries of 7 animals were performed in the study. The highest △QFR at 12 months was colocalized in segments of the grafts with the largest bending angles at baseline. Higher △QFR at 3 months were both at the anastomotic ends and were colocalized with the highest superficial wall strain at baseline. High baseline ESS was topographically associated with higher △QFR at the latest follow-up. Correlations of minimum and maximum ESS with △QFR at 3 months were the strongest among these parameters (ρ = 0.30, 95% CI [-0.05 to 0.56] and ρ = 0.27, 95% CI [-0.05 to 0.54], respectively).

CONCLUSIONS

Despite the limited number of grafts, this study suggests an association between early abnormal mechanical factors and late flow metrics of the grafts. The understanding of the mechanical characteristics could help to improve this novel conduit.

Quantitative flow ratio (QFR) identifies functional relevance of non-culprit lesions in coronary angiographies of patients with acute myocardial infarction

INTRODUCTION

In patients with acute myocardial infarction (AMI) and multivessel coronary disease, revascularization of non-culprit lesions guided by proof of ischemia usually requires staged ischemia testing. Quantitative flow ratio (QFR) has been shown to be effective in assessing the hemodynamic relevance of lesions in stable coronary disease. However, its suitability in AMI patients is unknown. In this study, we tested the diagnostic value of QFR based on acute angiograms (aQFR) during AMI to assess the hemodynamic relevance of non-culprit lesions.

METHODS

We retrospectively assessed the diagnostic efficiency of aQFR in 280 vessels from 220 patients, comparing it with staged ischemia testing using elective coronary angiography with FFR (n = 47), stress cardiac MRI (n = 200) or SPECT (n = 33).

RESULTS

aQFR showed a very good diagnostic efficiency (AUC = 0.887, 95% CI 0.832-0.943, p < 0.001) in predicting ischemia of non-culprit lesions, significantly superior to coronary lesion's geometry as assessed by quantitative coronary angiography. The optimal cut-off for aQFR to predict ischemia was 0.80 (sensitivity = 83.7%, specificity = 86.1%). Maintaining a predefined level of 95% sensitivity and specificity, we created a decision model based on aQFR: lesions with aQFR ≤ 0.75 should be treated, lesions with aQFR ≥ 0.92 do not yield any hemodynamic relevance, and lesions in the "grey zone" (aQFR 0.75-0.92) benefit from further ischemia testings. This model would allow to reduce staged ischemia tests by 46.8% without a relevant loss in diagnostic efficiency.

CONCLUSION

Our data demonstrate that aQFR allows an effective assessment of hemodynamic relevance of non-culprit lesions in AMI and may guide interventions of non-culprit coronary lesions.

Serial changes in the quantitative flow ratio in patients with intermediate residual stenosis after percutaneous coronary intervention

A beneficial surrogate marker for evaluating the effect of medical therapy is warranted to avoid deferred lesion revascularization. Similar to coronary artery imaging for monitoring the effects of medical therapy by analyzing plaque regression and stabilization, we hypothesized that evaluation of serial changes in the quantitative flow ratio (QFR) would serve as a surrogate marker of the effects of medical therapy against deferred lesion revascularization. Here, we investigated serial changes in QFR over time after percutaneous coronary intervention in patients who underwent medical therapy as a secondary prevention. Patients with intermediate stenosis in an untreated vessel observed at the baseline (BL) coronary angiography and follow-up (FU) coronary angiography performed 6-18 months after BL angiography were screened in 2 centers. A total of 52 patients were able to analyze both BL and FU QFR. The median QFR was 0.83 (IQR, 0.69, 0.89) at BL and 0.80 (IQR, 0.70, 0.86) at FU. The number of positive ΔQFR and negative ΔQFR were 21 and 31, respectively. The median ΔQFR was 0.05 (IQR, 0.03, 0.09) in positive ΔQFR and  - 0.05 (IQR,  - 0.07,  - 0.03) in negative ΔQFR (p < 0.0001). Univariate and multivariate analyses revealed that LDL-C at FU predicted improvement in the QFR (OR 0.95, 95% confidence interval [0.91, 0.98], P = 0.001). Assessment of serial changes in the QFR may serve as a surrogate marker for the effects of medical therapy in patients with residual intermediate coronary stenosis.

Angiography-based estimation of coronary physiology: A frame is worth a thousand words

Cumulative evidence has shown that coronary revascularization should be guided by functional significance of coronary lesions. Fractional flow reserve (FFR) is the gold standard for assessment of hemodynamic significance of coronary stenosis and FFR-guided percutaneous coronary intervention has improved clinical outcomes in patients with coronary artery disease. However, limitations of FFR such as increased operational time and cost, requirement of pressure wire and adenosine and technical difficulties have led to significant underutilization of the method in clinical practice. In the last few years, several methods of FFR estimation based on coronary angiography images have emerged to overcome invasive FFR limitations. The common elements of the novel indices include a 3D anatomical reconstruction of coronary vessels by angiographic projections and various approaches to fluid dynamics computation. Angiography-derived FFR methods have shown high diagnostic accuracy compared to invasive FFR. Although there are promising results regarding their prognostic role, large randomized trials evaluating clinical outcomes are lacking. The aim of this review is to present currently available angiography-derived FFR indices and highlight their differences, advantages, disadvantages and potential clinical implications.

Comparison of quantitative flow ratio and invasive physiology indices in a diverse population at a tertiary United States hospital

BACKGROUND

Quantitative flow ratio (QFR) is a technology to evaluate the coronary stenosis significance on 3-dimensional quantitative coronary angiography. The aim of this study is to evaluate and compare the QFR versus fractional flow reserve (FFR) and/or instantaneous free-wave ratio (iFR) in a US population with a fair African American population representation.

METHODS AND RESULTS

This was a retrospective, observational and single center study which enrolled 100 patients who underwent coronary angiography. The diagnostic performance of QFR in terms of sensitivity was 0.80 (95%CI 0.64-0.97) and specificity was 0.95 (95%CI 0.90-1.00), the positive predictive value (PPV) was 0.83 (0.68-0.98), while the NPV was 0.94 (0.88-0.99). The overall accuracy was 0.91 and area under curve (AUC) was 0.92 (95% CI 0.87-0.97). The R-squared was 0.54 and the Bland-Altman plot showed a bias of 0.0016 (SD 0.063) and limits of agreement (LOA): Upper LOA 0.13 and Lower LOA -0.12. In African Americans (n = 33), accuracy, AUC, sensitivity, specificity (94%; 0.90 (0.80-1.00); 0.90 (0.71-1.00); 0.96 (0.87-1.00), respectively) were better than those for the overall population.

CONCLUSIONS

In a US based representative population, vessel QFR accuracy and agreement with FFR as reference is high. Diagnostic performance of QFR in African Americans is also excellent.

Association of quantitative flow ratio-derived microcirculatory indices with anatomical-functional discordance in intermediate coronary lesions

Discrepancy between coronary lesion severity and functional significance has always been a relevant issue in the management of patients undergoing coronary angiography and/or revascularization. We sought to investigate the relationship between quantitative flow ratio (QFR)-derived microcirculatory indices and anatomical-functional mismatch/reverse mismatch in intermediate coronary lesions. Intravascular ultrasound (IVUS) imaging and QFR were analyzed in 117 de novo intermediate coronary lesions. Lesions with QFR ≤ 0.8 were considered hemodynamically significant. Anatomical significance of the lesions was defined according to the best cutoff value of combined IVUS parameters for predicting QFR ≤ 0.8. QFR-derived microcirculatory indices including contrast-flow QFR minus fixed-flow QFR (cQFR-fQFR), hyperemic flow velocity and angiography-derived index of microcirculatory resistance (IMR_angio) were calculated. The best cutoff values of IVUS parameters for predicting QFR ≤ 0.8 were minimum lumen area (MLA) 3.1mm² and plaque burden (PB) 70%, with area under the curve of 0.635 and 0.703, respectively. The total discordance rate of lesion functional significance between IVUS and QFR assessments was 26.5%, with 21 lesions (17.9%) being classified as mismatch (MLA ≤ 3.1mm² and PB ≥ 70% and QFR > 0.8) and 10 lesions (8.5%) as reverse-mismatch (MLA > 3.1 mm² or PB < 70% and QFR ≤ 0.8). At multivariate analysis, IMR_angio was identified as an independent predictor of mismatch (OR1.675, 95%CI:1.176-2.386, P = 0.004), whereas hyperemic flow velocity was identified as an independent predictor of reverse-mismatch (OR 1.233, 95%CI:1.073-1.416, P = 0.003). In intermediate coronary lesions, although MLA 3.1mm² and PB 70% determined by IVUS are predictive of QFR-defined functional significance, the discordance rate remains substantial. QFR-derived microcirculatory indices are independently associated with anatomical-functional discordance between IVUS and QFR assessments.

Angio-Based Fractional Flow Reserve, Functional Pattern of Coronary Artery Disease, and Prediction of Percutaneous Coronary Intervention Result: a Proof-of-Concept Study

PURPOSE

Wire-based coronary physiology pullback performed before percutaneous coronary intervention (PCI) discriminates coronary artery disease (CAD) distribution and extent, and is able to predict functional PCI result. No research investigated if quantitative flow ratio (QFR)-based physiology assessment is able to provide similar information.

METHODS

In 111 patients (120 vessels) treated with PCI, QFR was measured both before and after PCI. Pre-PCI QFR trace was used to discriminate functional patterns of CAD (focal, serial lesions, diffuse disease, combination). Functional CAD patterns were identified analyzing changes in the QFR virtual pullback trace (qualitative method) or after computation of the QFR virtual pullback index (QVP_index) (quantitative method). QVP_index calculation was based on the maximal QFR drop over 20 mm and the length of epicardial coronary segment with QFR most relevant drop. Then, the ability of the different functional patterns of CAD to predict post-PCI QFR value was tested.

RESULTS

By qualitative method, 51 (43%), 20 (17%), 15 (12%), and 34 (28%) vessels were classified as focal, serial focal lesions, diffuse disease, and combination, respectively. QVP_index values >0.71 and ≤0.51 predicted focal and diffuse patterns, respectively. Suboptimal PCI result (post-PCI QFR value ≤0.89) was present in 22 (18%) vessels. Its occurrence differed across functional patterns of CAD (focal 8% vs. serial lesions 15% vs. diffuse disease 33% vs. combination 29%, p=0.03). Similarly, QVP_index was correlated with post-PCI QFR value (r=0.62, 95% CI 0.50-0.72).

CONCLUSION

Our results suggest that functional patterns of CAD based on pre-PCI QFR trace can predict the functional outcome after PCI.

CLINICAL TRIAL REGISTRATION

ClinicalTrials.gov , number NCT02811796. Date of registration: June 23, 2016.

Feasibility and diagnostic reliability of quantitative flow ratio in the assessment of non-culprit lesions in acute coronary syndrome

Several studies have demonstrated the feasibility and safety of hemodynamic assessment of non-culprit coronary arteries in setting of acute coronary syndromes (ACS) using fractional flow reserve (FFR) measurements. Quantitative flow ratio (QFR), recently introduced as angiography-based fast FFR computation, has been validated with good agreement and diagnostic performance with FFR in chronic coronary syndromes. The aim of this study was to assess the feasibility and diagnostic reliability of QFR assessment during primary PCI. A total of 321 patients with ACS and multivessel disease, who underwent primary PCI and were planned for staged PCI of at least one non-culprit lesion were enrolled in the analysis. Within this patient cohort, serial post-hoc QFR analyses of 513 non-culprit vessels were performed. The median time interval between primary and staged PCI was 49 [42–58] days. QFR in non-culprit coronary arteries did not change between acute and staged measurements (0.86 vs 0.87, p = 0.114), with strong correlation (r = 0.94, p ≤ 0.001) and good agreement (mean difference -0.008, 95%CI -0.013–0.003) between measurements. Importantly, QFR as assessed at index procedure had sensitivity of 95.02%, specificity of 93.59% and diagnostic accuracy of 94.15% in prediction of QFR ≤ 0.80 at the time of staged PCI. The present study for the first time confirmed the feasibility and diagnostic accuracy of non-culprit coronary artery QFR during index procedure for ACS. These results support QFR as valuable tool in patients with ACS to detect further hemodynamic relevant lesions with excellent diagnostic performance and therefore to guide further revascularisation therapy.

Borderline coronary lesion assessment with quantitative flow ratio and its relation to the instantaneous wave-free ratio

PURPOSE

Quantitative flow ratio (QFR) is a recently developed image-based index for the assessment of borderline coronary artery disease. We sought to investigate a correlation between QFR and instantaneous wave-free ratio (iFR) for the assessment of intermediate coronary stenoses.

MATERIALS AND METHODS

Patients with borderline coronary lesions (40-90% by visual assessment) undergoing iFR assessment were enrolled. QFR was derived from a modeled hyperemic flow velocity derived from angiography without adenosine-induced hyperemia. Pressure wire-derived iFR served as the reference.

RESULTS

Values of QFR and iFR from 110 vessels with a mean percent diameter stenosis of 44.6 ​± ​12.0% were compared. Mean iFR was 0.90 ​± ​0.07 and 38 (34.5%) had iFR ≤0.89. Mean QFR was 0.81 ​± ​0.10 and 44 (40%) had QFR ≤0.80. A good agreement between QFR and iFR measurements was confirmed with a mean difference of 0.09 (95%CI -0.027 to 0.207) and intraclass correlation coefficient of 0.87 (95%CI 0.81-0.91). The overall diagnostic accuracy (AUC in ROC analysis) of QFR in detecting iFR ≤0.89 was 0.87 (95%CI 0.79-0.93; p ​< ​0.001). Regarding iFR ≤0.89, the optimal cutoff value of QFR was 0.79 with sensitivity, specificity, and accuracy of 76.3%, 83.3%, and 80.0%, respectively. A 100% sensitivity was observed for a QFR cutoff value of 0.88 and a 100% specificity for a QFR cutoff value of 0.69.

CONCLUSIONS

Our study confirmed good QFR diagnostic performance and correlation with iFR for detecting the functional ischemia caused by intermediate lesions in coronary arteries. However, the pressure wire assessment with iFR might be warranted in 2/3 of patients after QFR assessment.

Physiological benefits evaluated by quantitative flow ratio in patients with reduced left ventricular ejection fraction who underwent percutaneous coronary intervention

BACKGROUND

To explore the clinical benefits of revascularization in patients with different levels of left ventricular ejection fraction (LVEF) from the perspective of quantitative flow ratio (QFR).

METHODS

Patients who underwent successful percutaneous coronary intervention (PCI) and one-year angiographic follow-up were retrospectively screened and computed by QFR analysis. Based on their LVEF, 301 eligible patients were classified into reduced LVEF (≤ 50%, n = 48) and normal LVEF (> 50%, n = 253) groups. Pre-PCI QFR, post-PCI QFR, follow-up QFR, late lumen loss (LLL), LVEF and major adverse cardiovascular and cerebrovascular events (MACCEs) at one year were compared between groups.

RESULTS

The reduced LVEF group had a lower mean pre-PCI QFR than the normal LVEF group (0.67 ± 0.16 vs. 0.73 ± 0.15, p = 0.004), but no significant difference was found in the post-PCI or one-year follow-up QFR. No association was found between LVEF and QFR at pre-PCI or follow-up. The reduced LVEF group had greater increases in QFR (0.27 ± 0.18 vs. 0.22 ± 0.15, p = 0.043) and LVEF (6.05 ± 9.45% vs. - 0.37 ± 8.11%, p < 0.001) than the normal LVEF group. The LLL results showed no difference between the two groups, indicating a similar degree of restenosis. The reduced LVEF group had a higher incidence of MACCEs (14.6% vs. 4.3%, p = 0.016), which was mainly due to the higher risk of heart failure (6.3% vs. 0%, p = 0.004).

CONCLUSION

Compared to the corresponding normal LVEF patients, patients with reduced LVEF who underwent successful PCI were reported to have greater increases in QFR and LVEF, a similar degree of restenosis, and a higher incidence of MACCEs due to a higher risk of heart failure. It seems that patients with reduced LVEF gain more coronary benefits from successful revascularization from the perspective of flow physiology evaluations.

Short- and long-term functional results following drug-coated balloons versus drug- eluting stents in small coronary vessels: The RESTORE quantitative flow ratio study

Background Immediate and long-term functional outcomes after percutaneous treatment of small vessel disease (SVD) with drug-coated balloon (DCB) versus drug-eluting stent (DES) remain unknown. The study sought to investigate whether treatment of de novo SVD with DCB yields similar functional results compared with DES, as judged with angiography-based quantitative flow ratio (QFR). Methods and results QFR was measured at pre-procedural, post-procedural and 9-month angiography in all available subjects from the non-inferiority RESTORE SVD China trial, in which patients were randomized to Restore DCB (n = 116) or Resolute DES (n = 114) study arms. Primary outcome of this analysis was 9-month QFR. Pre-procedural, post-procedural and 9-month QFR was performed in 84.8% (195/230), 83.0% (191/230) and 93.8% (181/193) cases, respectively. At 9 months, the QFR of DCB showed no significant difference to DES (0.88 ± 0.23 vs. 0.92 ± 0.12, p = 0.12). Both 9-month QFR and the QFR difference between post-procedure and 9-month follow-up were correlated with angiographic percentage of diameter stenosis and late loss, and predictive of 2-year clinical outcome. Conclusions Treatment of coronary SVD with DCB resulted in similar 9-month functional results compared with DES. This study provides evidences to the value of QFR as a mean of evaluating device performance after coronary revascularization. Clinical trial registration URL: https://www.clinicaltrials.gov; ClinicalTrial.gov: Identifier: NCT02946307.

Clinical implication of QFR in patients with ST-segment elevation myocardial infarction after drug-eluting stent implantation

The feasibility and prognostic value of quantitative flow ratio (QFR) after percutaneous coronary intervention (PCI) in ST-segment elevation myocardial infarction (STEMI) patients have not been assessed. The aim of this study was to investigate the prognostic utility of post-PCI QFR to predict outcomes in STEMI and determine the influence of functional results, in both culprit and nonculprit lesions, after PCI. Patients undergoing PCI of culprit lesions and receiving staged procedures of nonculprit lesions after 7 days were enrolled from 2 centers and underwent post-PCI QFR. The primary outcome was the vessel-oriented composite endpoints (VOCEs), defined as vessel-related cardiovascular death, vessel-related myocardial infarction, and target vessel revascularization. Four hundred fifteen vessels (186 culprit lesions and 219 nonculprit lesions) in 186 patients were analyzed. Measured at staged PCI, the post-PCI QFR of culprit lesions was significantly lower than that of nonculprit lesions (0.92 ± 0.10 versus 0.95 ± 0.08, p < 0.001). The multivariable model demonstrated that low post-PCI QFR was an independent predictor of 2-year VOCE (20.8% versus 5.7%; hazard ratio 2.718; 95% CI 1.347-5.486; p = 0.005). In STEMI patients with a low angiography-derived index of microcirculatory resistance (≤ 40U), a good correlation and agreement between post-PCI QFR value of culprit lesions at primary and staged procedures (r = 0.942; mean difference: - 0.0017 [- 0.074 to 0.070]) was identified. In conclusion, culprit lesions suffered from suboptimal functional results more frequently compared to nonculprit lesions after PCI in STEMI patients. Low post-PCI QFR was associated with subsequent adverse clinical outcomes. After stenting, culprit lesions may feasibly be assessed through QFR without significant microvascular dysfunction.

Clinical relevance and prognostic implications of contrast quantitative flow ratio in patients with coronary artery disease

BACKGROUND

We sought to evaluate the diagnostic performance of contrast quantitative flow ratio (cQFR) in all-comer patients with coronary artery disease, and to compare the vessel-oriented composite outcomes (VOCO) according to cQFR values.

METHOD

599 vessels with 452 patients who underwent clinically indicated fractional flow reserve (FFR) and cQFR measurement were evaluated. The cQFR, derived from 3-dimensional quantitative coronary angiography combined with TIMI frame-counts was compared with FFR as a reference standard. The risk of VOCO at 2 years, a composite of cardiac death, target-vessel myocardial infarction, and ischemia-driven target lesion revascularization, was compared according to cQFR and FFR value.

RESULTS

cQFR strongly correlated with FFR (r=0.860, p<0.001) and showed diagnostic accuracy of 91.2% to predict FFR≤0.80. cQFR showed significantly higher c-index to predict FFR≤0.80 (0.953, 95%CI 0.937-0.969) than %DS, percent area stenosis, resting distal coronary pressure/aortic pressure, and fixed QFR (p<0.001). Diagnostic accuracy of cQFR was not different according to various subgroups including non-culprit vessel of acute coronary syndrome and diabetes mellitus. Vessels with low cQFR (≤0.80) showed a significantly higher risk of VOCO at 2-year compared to those with high cQFR (>0.80) (HR 4.650, 95%CI 1.254-17.240, p=0.022). Discriminatory ability of cQFR for VOCO was similar with that of FFR (0.672 vs. 0.643, p=0.147).

CONCLUSION

cQFR showed excellent correlation and diagnostic accuracy with FFR in diverse clinical presentations or patient characteristics. Low cQFR was significantly associated with a higher risk of VOCO at 2 years compared with high cQFR and cQFR showed similar discriminatory ability for VOCO with FFR.

Angiography-derived index of microcirculatory resistance as a novel, pressure-wire-free tool to assess coronary microcirculation in ST elevation myocardial infarction

Immediate assessment of coronary microcirculation during treatment of ST elevation myocardial infarction (STEMI) may facilitate patient stratification for targeted treatment algorithms. Use of pressure-wire to measure the index of microcirculatory resistance (IMR) is possible but has inevitable practical restrictions. We aimed to develop and validate angiography-derived index of microcirculatory resistance (IMR_angio) as a novel and pressure-wire-free index to facilitate assessment of the coronary microcirculation. 45 STEMI patients treated with primary percutaneous coronary intervention (pPCI) were enrolled. Immediately before stenting and at completion of pPCI, IMR was measured within the infarct related artery (IRA). At the same time points, 2 angiographic views were acquired during hyperaemia to measure quantitative flow ratio (QFR) from which IMR_angio was derived. In a subset of 15 patients both IMR and IMR_angio were also measured in the non-IRA. Patients underwent cardiovascular magnetic resonance imaging (CMR) at 48 h for assessment of microvascular obstruction (MVO). IMR_angio and IMR were significantly correlated (ρ: 0.85, p < 0.001). Both IMR and IMR_angio were higher in the IRA rather than in the non-IRA (p = 0.01 and p = 0.006, respectively) and were higher in patients with evidence of clinically significant MVO (> 1.55% of left ventricular mass) (p = 0.03 and p = 0.005, respectively). Post-pPCI IMR_angio presented and area under the curve (AUC) of 0.96 (CI95% 0.92–1.00, p < 0.001) for prediction of post-pPCI IMR > 40U and of 0.81 (CI95% 0.65–0.97, p < 0.001) for MVO > 1.55%. IMR_angio is a promising tool for the assessment of coronary microcirculation. Assessment of IMR without the use of a pressure-wire may enable more rapid, convenient and cost-effective assessment of coronary microvascular function.

Diagnostic performance of angiography-based quantitative flow ratio for the identification of myocardial ischemia as assessed by 13N-ammonia myocardial perfusion imaging positron emission tomography

BACKGROUND

Quantitative flow ratio (QFR) is a novel, adenosine-free method for functional lesion interrogation based on 3-dimensional quantitative coronary angiography and computational algorithms. We sought to investigate the diagnostic performance of QFR versus myocardial perfusion imaging positron emission tomography (MPI-PET), which yields the highest accuracy for detection of myocardial ischemia.

METHODS

Diagnostic performance of QFR versus MPI-PET was assessed in consecutive patients undergoing both clinically indicated coronary angiography and ¹³N-ammonia MPI-PET within a six-month period.

RESULTS

Out of 176 patients (439 coronary arteries), 19.3% were women. Percent area stenosis was 45 [32-58] %. Myocardial ischemia on ¹³N-ammonia MPI-PET was detected in 106 (24.1%) vessel territories and hemodynamic significance defined as contrast-flow vessel QFR ≤ 0.80 was observed in 83 (18.9%) vessels. Diagnostic accuracy, sensitivity, and specificity of contrast-flow vessel QFR for the prediction of myocardial ischemia on ¹³N-ammonia MPI-PET were 92.5 (95% CI 89.6-94.7) %, 73.6 (95% CI 64.1-81.7) %, and 98.5 (95% CI 96.5-99.5) %, respectively. The AUCs for contrast-flow vessel QFR, percent diameter stenosis, and percent area stenosis were 0.85 (95% CI 0.81-0.88, p < 0.001), 0.76 (95% CI 0.71-0.79, p < 0.001) and 0.75 (95% CI 0.70-0.79, p < 0.001), respectively.

CONCLUSIONS

QFR, a novel diagnostic tool for functional coronary lesion assessment, provides good diagnostic agreement with MPI-PET and superior diagnostic accuracy for the detection of myocardial ischemia as compared to anatomic indices. Future studies will have to determine the non-inferiority of QFR to fractional flow reserve with respect to clinical outcomes.

A Dan-NICAD substudy

Quantitative flow ratio (QFR) and fractional flow reserve (FFR) have not yet been compared head to head with perfusion imaging as reference for myocardial ischemia. We aimed to compare the diagnostic accuracy of QFR and FFR with myocardial perfusion scintigraphy (MPS) or cardiovascular magnetic resonance (CMR) as reference. This study is a predefined post hoc analysis of the Dan-NICAD study (NCT02264717). Patients with suspected coronary artery disease by coronary computed tomography angiography (CCTA) were randomized 1:1 to MPS or CMR and were referred to invasive coronary angiography with FFR and predefined QFR assessment. Paired data with FFR, QFR and MPS or CMR were available for 232 vessels with stenosis in 176 patients. Perfusion defects were detected in 57 vessel territories (25%). For QFR and FFR the diagnostic accuracy was 61% and 57% (p = 0.18) and area under the receiver operating curve was 0.64 vs. 0.58 (p = 0.22). Stenoses with absolute indication for stenting due to diameter stenosis > 90% by visual estimate were not classified as significant by either QFR or MPS/CMR in 21% (7 of 34) of cases. The diagnostic performance of QFR and FFR was similar but modest with MPS or CMR as reference. Comparable performance levels for QFR and FFR are encouraging for this pressure wire-free diagnostic method.

Comparison of quantitative flow ratio value of left anterior descending and circumflex coronary artery in patients with Takotsubo syndrome

Takotsubo syndrome (TTS) is an acute cardiac event without epicardial coronary obstruction but often with reversible ventricular motion abnormalities. Quantitative flow ratio (QFR) is a novel approach to evaluate the coronary stenosis significance on the basis of 3-dimensional quantitative coronary angiography (3D-QCA) and contrast flow by Thrombolysis in Myocardial Infarction frame count. This study aimed to evaluate and compare the QFR value in the left anterior descending artery (LAD) and the left circumflex artery (LCx) in patients with TTS. This retrospective and observational study enrolled 30 patients with TTS who underwent coronary angiography. We evaluated the QFR data using the 3D-QCA analysis and compared the QFR data in the LAD and the LCx. No significant differences were observed in terms of flow velocity, percent diameter stenosis, minimum lumen diameter, and reference diameter between LAD and LCx. However, vessel QFR in the LAD was significantly reduced compared with that in the LCx (0.98 [0.94 to 0.99] vs. 1.00 [0.99 to 1.00], P < 0.001). Ejection fraction at baseline and initial troponin-I levels were not correlated with the vessel QFR both in the LAD and the LCx. The QFR value in the LAD was significantly reduced compared to that in the LCx in patients with TTS.