Quantitative Flow Ratio Research Articles

Diagnostic Performance of Quantitative Flow Ratio for the Assessment of Non-Culprit Lesions in Myocardial Infarction (QFR-OUTSMART): Systematic Review and Meta-Analysis.

Quantitative flow ratio (QFR) analysis is a simple and non-invasive coronary physiological assessment method with evidence for evaluating stable coronary artery disease with correlation to fractional flow reserve (FFR). However, there is no evidence to recommend its use in non-culprit lesions (NCLs) in myocardial infarction (MI). We performed a systematic review and meta-analysis using the PRISMA and PROSPERO statements. The study's primary objective was to assess the diagnostic accuracy of QFR in identifying functionally significant NCLs after MI based on invasive FFR and non-hyperemic pressure ratios as references. We obtained values of the area under the curve (AUC), sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV). We performed a leave-one-out sensitivity analysis for each study's impact on the overall effect. We included eight studies, with 713 patients and 920 vessels evaluated with QFR. The overall AUC was 0.941 (I2 = 0.559, p < 0.002), with a sensitivity of 87.3%, a specificity of 89.4%, a PPV of 86.6%, and an NPV of 90.1%. Compared to FFR, we found an AUC of 0.957 (I2 = 0.331, p < 0.194), a sensitivity of 89.6%, a specificity of 89.8%, a PPV of 88.3%, and an NPV of 91%. The sensitivity analysis showed a similar diagnostic performance in both studies. QFR is effective in analyzing NCLs with a significant diagnostic yield compared to FFR, with an excellent AUC in MI patients. Performing prospective multicenter studies to characterize this population and reproduce our results is essential.

Hemodynamic assessment of intracranial atherosclerotic stenosis: comparison between invasive non-hyperemic pressure ratio and angiography-derived quantitative flow ratio

ObjectivesTo evaluate the diagnostic accuracy of the quantitative flow ratio (QFR) for hemodynamic exploration of intracranial atherosclerotic stenosis, using the invasive cerebrovascular pressure ratio (CVPR) and resting full-cycle ratio (RFR) as reference standards.Materials and methodsPatients with symptomatic unifocal intracranial atherosclerotic stenosis were included. The CVPR was defined as the ratio of the proximal and distal pressures. All patients underwent angioplasty under general anesthesia. The QFR was calculated based on digital subtraction angiography. Using the CVPR as a reference, we compared its correlation with the QFR across different degrees and locations of stenosis.ResultsThe CVPR and QFR were measured in 34 vessels of 32 patients. The QFR demonstrated a high correlation and excellent agreement(r = 0.8227, p &amp;lt; 0.001) with the CVPR in distal stenosis before intervention. In the subgroup with diameter stenosis &amp;gt;80%, the QFR showed a high correlation (r = 0.8812, p &amp;lt; 0.001) with the CVPR. In the anterior circulation subgroup, the QFR showed an excellent correlation (r = 0.9066, p &amp;lt; 0.001) with the CVPR. In the posterior circulation subgroup, the QFR showed a high correlation with the CVPR (r = 0.7706, p &amp;lt; 0.001). Diameter stenosis rates showed a moderate negative correlation with the CVPR.ConclusionThere was a strong correlation between the QFR and wire-based CVPR, especially for anterior circulation lesions before intervention. The QFR may serve as a predictive factor for evaluating hemodynamic changes in intracranial atherosclerotic stenosis.

Diagnostic accuracy of automatic quantitative flow ratio for hemodynamic assessment of coronary artery stenosis: prospective observational study

Abstract Background Quantitative flow ratio (QFR) is a method for evaluating fractional flow reserve (FFR) without the use of an invasive coronary pressure wire or pharmacological hyperemic agent. Automatic QFR (auto QFR) is a recently developed, simpler method of calculating QFR that uses a patient-specific TIMI (Thrombolysis in Myocardial Infarction) frame count, but with automatically specified start and end frames. Although the previous studies demonstrated that contrast QFR is more accurate than fixed QFR, there is no evidence for auto QFR. Purpose The aim of this study was to evaluate the diagnostic performance of auto QFR, fixed QFR, and contrast QFR for the diagnosis of hemodynamically significant coronary stenosis defined by FFR ≤0.80. Methods This prospective, multicentre trial enrolled patients suspected with coronary artery disease undergoing diagnostic coronary angiography with an indication for to perform invasive FFR. QFR was calculated at a blinded core laboratory. The primary endpoint was the diagnostic accuracy of auto QFR, fixed QFR, and contrast QFR to determine hemodynamically significant coronary stenosis using invasive FFR (≤0.80) as a reference standard. Results A total of 325 vessels from 274 patients were analysed. Mean FFR was 0.82±0.09, mean auto QFR was 0.80±0.12, and mean contrast QFR was 0.82±0.11, respectively. The overall diagnostic accuracy for identifying an FFR of ≤0.80 was highest by contrast QFR (81.5%), followed by fixed QFR (79.1%), and auto QFR (77.5%). The AUC was higher for contrast QFR (AUC 0.885; 95% CI: 0.845-0.925) than fixed QFR (AUC 0.856; 95% CI: 0.812-0.900) or auto QFR (AUC 0.854; 95% CI: 0.806-0.901), but did not differ significantly between fixed QFR and auto QFR (Figure). Conclusions There was no significant difference in AUC between fixed and auto QFR, but the accuracy of contrast QFR was significantly higher compared to both QFRs. Auto QFR has the advantage of faster computation time while using patient-specific coronary flow, but accuracy still needs to be improved.

Comparison of vessel-Fractional Flow Reserve (vFFR) and Quantitative Flow Ratio (QFR) using instantaneous wave-Free Ratio (iFR) or Resting Full-cycle Ratio (RFR) as reference

Abstract Background Angiography-based functional assessment remains the state of the art to assess the hemodynamic relevance of intermediate coronary stenoses. In addition to fractional flow reserve (FFR), adenosin free indices like instantaneous wave-free ratio (iFR) or resting full-cycle ratio (RFR) are widely used for the invasive evaluation. Although these methods are widely accepted, they are underused in clinical routine due to costs, their invasive nature, longer procedural times, and lack of availability. Vessel-fractional flow reserve (vFFR) and quantitative flow ratio (QFR) are new software-based methods for the evaluation of coronary-physiology. The aim of this study is to compare vFFR and QFR with the established invasive methods iFR or RFR. Methods We prospectively analyzed 95 Patients in our QFR-Registry vFFR- and QFR-computation was performed three-times by two certified, blinded, and independent experts using the QAngio XA 3D 3.2- and CAAS-software, respectively. Results: 101 main epicardial coronary arteries (52 LAD; 19 LCx; 30 RCA) were analyzed using vFFR, QFR and iFR or RFR. vFFR showed a good correlation with adenosine-free indices in all 3 measurements (AUC 0.883 with r=0.672, p&amp;lt;0.001; AUC 0.841 with r=0.618 p&amp;lt;0.001; AUC 0.840 with r=0.592, p&amp;lt;0.001 respectively). The diagnostic accuracy between the three vFFR-measurements and iFR/RFR was 83%; 81% and 79% respectively. QFR-computations showed a similar correlation with iFR/RFR (AUC 0.899 with r=0.720, p&amp;lt;0.001; AUC 0.919 with r=0.649, p&amp;lt;0.001; AUC 0.930 with r=0.703, p&amp;lt;0.001 respectively) with a diagnostic accuracy 88%, 89% and 88% respectively. The intra- and inter-observer reliability for vFFR (intra: mean difference 0.002±0.0568; inter: 0.024±0.054) and QFR (intra: mean difference 0.018±0.071; inter: 0.016±0.075) analyzed in a Bland-Altman Blot showed a good correlation between virtual assessments and invasive measurements with iFR/RFR. Conclusion The data show a good diagnostic agreement between vFFR and QFR and adenosine free invasive assessments. vFFR and QFR appear reasonable alternative approaches for the evaluation of intermediate stenoses. These data provide the rational to prospectively test for a clinical noninferiority of the non-invasive flow measurements.Diagnostic performance of vFFR/cQFR

Impact of preoperative quantitative flow ratio on long term coronary artery bypass grafts patency

Abstract Background Preoperative fractional flow reserve (FFR) in the native coronaries is a known predictor of long-term graft patency after coronary artery bypass graft (CABG) surgery. Quantitative flow ratio (QFR) is an angiogram-based functional assessment tool of coronary stenoses. Its predictive value of graft patency is unknown. Purpose To investigate the impact of preoperative QFR value on long-term graft patency after CABG. Methods In this retrospective multicentric study we included consecutive patients treated with CABG between 2011 and 2022, with available coronary angiogram before and at any timepoint after CABG. Three-vessel QFR analysis of the preoperative angiography has been performed. Follow-up angiography was checked for graft patency. Only vessels entered the analysis for which baseline QFR was appropriate and which has been bypassed. Results 400 patients were included with mean age of 67±8 years. They received on average 2.0±0.9 bypasses. 788 coronaries and bypasses were analyzed, among the latter 455 were arterial and 333 were veins. 37% were placed on LAD, 26% on RCA and 26% on the LCx. Stenosis severity at baseline was 73±22% with a QFR value of 0.68±0.30. Follow-up angiographies were performed at 34±29 months. Overall graft patency was 83%, with higher occlusion rate for venous than arterial conduits (27% vs 9%, respectively; HR 3.9 [2.60-5.88]). Occlusion rate was lower for grafts implanted on QFR significant native vessels versus those, placed on non-significant ones (13% vs 30%, respectively; HR 2.86 [1.93-4.26]). Benefit was maintained for both, arterial (5% vs 22%, respectively; HR 5.23 [2.78-10.38]), as well as for venous conduits (24% vs 39%; HR 2.09 [1.21-3.50]). Conclusion QFR significantly predicts graft patency irrespective of whether the graft is arterial or venous. However, patency of venous grafts is poor, even if implanted on functionally significant native stenotic coronaries.Graft patency

Clinical value of single projection angiography-derived FFR in non-infarct related artery

Abstract Background Murray law-based quantitative flow ratio (μFR) is an emerging technique which requires only one projection of coronary angiography with similar accuracy with quantitative flow ratio (QFR). However, it has not been validated for evaluation of non-infarct related artery (non-IRA) in acute myocardial infarction (AMI) setting. Therefore, our study aimed to evaluate the diagnostic accuracy of μFR and the safety of deferring non-IRA lesion with μFR&amp;gt;0.80 in the setting of AMI. Methods μFR and QFR were analyzed for non-IRA lesions of AMI patients enrolled in the FRAME-AMI trial, consisting of fractional flow ratio (FFR)-guided PCI and angiography-guided PCI groups. Diagnostic accuracy of μFR was compared to QFR and FFR. Patients were classified by non-IRA μFR values 0.80 as a cutoff value. The primary outcome was vessel-oriented composite outcomes (VOCO), a composite of cardiac death, non-IRA-related MI, and non-IRA-related repeat revascularization. Results 443 patients (552 lesions) were eligible for μFR and QFR analysis. μFR showed acceptable correlation with FFR (R=0.777, P&amp;lt;0.001), comparable C-index with QFR to predict FFR≤0.80 (μFR vs. QFR: 0.926 vs. 0.961, P=0.070), and shorter total analysis time (mean 32.7sec vs. 186.9sec, P&amp;lt;0.001). Non-IRA with μFR&amp;gt;0.80 and deferred PCI had significantly lower risk of VOCO than non-IRA with performed PCI (3.4% vs. 10.5%; HR, 0.37; 95% CI, 0.14-0.99; P=0.048). Conclusion In multivessel AMI patients, μFR of non-IRA showed acceptable diagnostic accuracy comparable to that of QFR to predict FFR≤0.80. Deferred non-IRA with μFR&amp;gt;0.80 showed lower risk of VOCO than revascularized non-IRA.

Prognostic role of post-percutaneous coronary intervention quantitative flow ratio

Abstract Background/Introduction Accumulated evidence supports the prognostic value of post–percutaneous coronary intervention (PCI) physiological measurement. Quantitative Flow Ratio (QFR) is a well-studied angiography-based method for functional assessment. Purpose To investigate the possible prognostic implications of post-PCI QFR in patients undergoing revascularization. Methods We performed offline QFR analysis in all-comers undergoing PCI in a single center. A cut-off value of 0.8 was used to classify patients in high post-PCI QFR group (&amp;gt;0.8) and low post-PCI QFR group (≤0.8). Patients with at least one vessel with post-PCI QFR ≤0.8 were classified in the low post-PCI QFR group. Primary endpoint was the composite outcome of death, myocardial infraction, ischemia-driven revascularization, and heart failure-related hospitalization. Results We included 297 patients in the study. Mean age was 64 (±11) years and 81% of patients were male. Number of patients presented with chronic coronary syndrome was comparable to that of patients presented with acute coronary syndrome (52.9 vs 47.1 %, respectively). Patients in the low post-PCI QFR group had more often diabetes mellitus, lower left ventricular ejection fraction (LVEF) and higher SYNTAX score compared to patients in the high post-PCI QFR group. Median follow-up period was 29 (26-34) months. After adjusting for covariates, low post-PCI QFR was independently associated with higher rate of the composite outcome (HR: 2.22 95% CI 1.01-4.88, p=0.047). Conclusions In our study, patients with lower post-PCI value were independently associated with higher risk of cardiovascular adverse events.

Comparison of fully angiography-derived versus a hybrid of angiography and pressure-wire-derived approach to assess coronary microvascular resistance: the OxAMI-Hybrid study

Abstract Background Despite growing evidence of its clinical implications, assessment of coronary microvascular dysfunction (CMD) remains limited in routine clinical practice. Hence, there is an increasing interest in angiography-derived indices to encourage assessment of CMD in the cardiac catheterisation laboratory. We investigate here a novel approach, IMRhybrid, using a combination of pressure-wire-based assessment of distal coronary pressure (Pd) and an angiography-derived surrogate of coronary flow. Methods Patients were enrolled to the OxAMI-Hybrid study. The accuracy of IMRhybrid was assessed in diagnosing CMD using fully pressure wire and bolus thermodilution Index of Microcirculatory Resistance (IMR) as a reference. The accuracy of IMRhybrid was then compared against a fully angiography-derived index of microvascular resistance (IMRangio). Based on previous work, angiography-derived IMR, IMRangio, was calculated as IMRangio = Quantitative Flow Ratio (QFR) ado x Pahyperaemia x TIMI Frame Count (TFC) hyperaemia / Frame Rate. Conversely, IMRhybrid was expressed as IMRhybrid = Pdhyperaemia x TFChyperaemia / Frame Rate, where frame rate was fixed at 15 frame per second for both indices. In both cases, TFC/frame rate represented angiography-derived mean transit time, mTt in hyperaemia. Results 60 patients were enrolled prospectively, of which 28 with acute coronary syndrome and 32 with stable coronary artery disease. A total of 66 vessel analyses were performed. Both IMRhybrid and IMRangio correlated with IMR (rho=0.51, p &amp;lt;0.001 and rho=0.51, p &amp;lt;0.001 respectively) and showed good and comparable overall diagnostic accuracy in predicting IMR ≥ 25 (83.3% and 75.4% respectively) with a receiver operator curve (ROC) analyses showing an AUC of 0.82 and 0.81 respectively (p for comparison= 0.97). Conclusion Both approaches, IMRhybrid and IMRangio provide viable and comparable methods of assessing CMD which correlate with bolus thermodilution-based IMR, retaining good diagnostic accuracy. IMRhybrid is a simple alternative to conventional bolus thermodilution-based IMR, offering the advantage of being suitable with any pressure wire system.A: IMR, B: QFR, C: TFCA+C: IMRhybrid, B+D: IMRangio

Comparative analysis of post-PCI fractional flow reserve and quantitative flow ratio in predicting long-term Target Vessel Failure and hard endpoints

Abstract Background The role of functional assessment after angiographically acceptable post-PCI result is debatable. Purpose We sought to investigate the correlation between Fractional Flow Reserve measured directly after drug eluting stent (DES) implantation (post-PCI FFR) and post-PCI Quantitative Flow Ratio (post-PCI QFR), clarify their relationship with clinical parameters, and long-term target vessel failure (TVF: cardiac death (CD), non-fatal target vessel myocardial infarction (MI) and target vessel revascularisation (TVR)), and a composite of CD and MI (CD/MI). Method Coronary arteries that underwent post-PCI FFR measurement at our centre between 2012 and January 2021 were consecutively included in this registry. Post-PCI QFR was calculated blinded to the post-PCI FFR value. We analysed the influence of LAD vs. (non-LAD) location, gender, age, hypertension, diabetes mellitus, hyperlipidemia, indication (acute (ACS) vs. chronic coronary syndrome), stent diameter, in-stent restenosis (ISR) vs. de novo lesion category, estimated glomerular filtration rate, proximal vs. distal lesions, severe aortic stenosis, atrial fibrillation during the procedure (AF), and prior myocardial infarction in the supply area (prior MI) on post-PCI FFR and QFR. Optimal cut-off was determined by ROC curves. Results A total of 400 coronary arteries were analysed. LAD location (p&amp;lt;0.001), male gender (p=0.0029) and smaller stent diameter (p=0.0073) proved to be predictors of a lower post-PCI FFR. LAD location (p=0.001), ISR (p=0.02), distal location (p=0.0019), AF (p=0.042) and prior MI (p=0.029) were predictors of a lower post-PCI QFR. There was a systematic bias in post-PCI QFR compared to post-PCI FFR (bias 0.0614, 95% CI, 0.053 - 0.069). During a median follow-up of 45 months, 31 CD, 20 MI and 35 TVR occurred. Follow-up was complete in 100%. There was a significant inverse correlation between post-PCI FFR and TVF (p&amp;lt;0.001) as well as between post-PCI QFR and TVF (p=0.045). In-stent restenosis (p=0.014) and prior MI (p=0.002) were also predictors of higher TVF rate. The predictors of CD/MI were lower post-PCI FFR (p&amp;lt;0.001), smaller stent diameter (p=0.03), higher age (p=0.031) and ACS indication (p=0.048), whereas post-PCI QFR was not. The best post-PCI FFR cut-off to predict TVF was 0.87 (p&amp;lt;0.0001). There was no single optimal post-PCI QFR cut-off to predict TVF. Conclusion Post-PCI QFR shows a systematic bias compared to post-PCI FFR. Post-PCI FFR is a significant predictor of TVF as well as CD/MI, whereas post-PCI QFR predicts TVF. No significant correlation between post-PCI QFR and CD/MI could be demonstrated. Our findings underscore the importance of considering multiple clinical parameters in predicting long-term outcomes. The best post-PCI FFR cut-off to predict TVF was 0.87. However, there was no single, universally applicable post-PCI QFR threshold to predict TVF.

Association between stent implantation results and target vessel failure after IVUS-Guided PCI: A FLAVOUR substudy

Abstract Background Despite substantial advancements in coronary stent systems and implantation techniques, target vessel failure (TVF) remains a clinical issue to be addressed. Purpose We used deep learning algorithms for automatic stent analysis of intravascular ultrasound (IVUS) data to identify stent implantation characteristics associated with TVF. Methods In patients from the IVUS-guided group of the FLAVOUR trial who had undergone successful stenting, validated deep learning algorithms were applied to IVUS images to delineate plaque and stent strut for the quantification of stent expansion, apposition, and residual plaque burden. Stent overexpansion was defined as stent area exceeding 120% of the hypothetical healthy lumen area. Murray law-based quantitative flow ratio (μQFR) was also assessed from angiographic images. The primary endpoint was TVF at 2 years, defined as a composite of cardiac death, target vessel-related myocardial infarction, and ischemia-driven target vessel revascularization. Results A total of 459 vessels in 441 patients were included, with TVF events occurred in 15 vessels (3.3%) during the 2-year follow-up. Stent analysis was performed in 687,379 stent struts from 70,369 IVUS image frames of the interrogated vessels with the assistance of specific deep learning algorithms. On vessel-level multivariate analysis adjusting for procedural covariates, stent overexpansion length &amp;gt;5 mm (hazard ratio, 4.57; 95% confidence interval [CI], 1.31 to 15.92; P=0.017), residual plaque burden at proximal stent edge &amp;gt;50% (hazard ratio, 3.34; 95% CI, 1.19 to 9.33; P=0.022), and post-PCI μQFR &amp;lt;0.90 (hazard ratio, 5.09; 95% CI, 1.62 to 15.97; P=0.005) were more likely to be present in vessels with TVF events than in those without. Conclusions Besides the established indexes of post-procedural residual plaque burden and low μQFR, deep learning-powered IVUS stent overexpansion was significantly associated with increased risk of TVF.Suboptimal stenting results and TVF

Changes of angiography-derived coronary microcirculatory resistance before and after drug-coated balloon treatment

Abstract Background Drug coated balloon (DCB) is a treatment option for a lesion in a small coronary artery. The effect of DCB is proven in mechanistic and clinical outcomes, however, its influence on the microvascular function has not been elucidated. In addition, because there are differences in the types of drugs and coatings among different DCBs, their effects on microvascular function may vary. Angiography-derived microcirculatory resistance (AMR) is a novel angiographic parameter calculated from angiography-derived quantitative flow ratio and flow velocity estimation. AMR is reported to have a good correlation with the wire-based index of microvascular resistance. Purpose To investigate the AMR in coronary vessels treated with sirolimus or paclitaxel coated balloon. Methods This is a subanalysis of the TRANSFORM I (The TReAtmeNt of Small Coronary Vessels: MagicTouch Sirolimus Coated Balloon) trial. TRANSFORM I is a prospective, randomized, multi-center, open-label noninferiority trial conducted in Europe that enrolled 121 patients (126 vessels) with stabilized acute coronary syndrome or chronic coronary syndrome who had at least one de novo coronary artery lesion in a small coronary vessel. Patients were randomized 1:1 to treatment with the sirolimus coated balloon (SCB) or paclitaxel coated balloon (PCB). The SCB is coated with phospholipid encapsulated sirolimus nanocarrier, whereas the PCB is coated with crystalline paclitaxel. In this subanalysis, angiography at baseline and post-procedure were analyzed to calculate the AMR by an imaging core lab. Coronary microvascular dysfunction (CMD) was defined as AMR≧2.5 mmHg*s/cm. Results In the total of 126 vessels, 63 were included in each of the SCB and PCB group. Angiography both at baseline and post-procedure were analyzable for AMR in 59 vessels in SCB and in 59 vessels in PCB group. In SCB group, the median AMR increased significantly after procedure (baseline; 2.03 [1.58-2.42], post-procedure;2.21 [1.78-2.53], p=0.03). However, the proportion of vessels with CMD did not significantly change (baseline; 22.0% [13/59], post-procedure; 32.2% [18/59], p=0.19) (Figure). In the PCB group, the median AMR increased significantly after procedure (baseline; 2.22 [1.66-2.53], post-procedure;2.45 [1.93-2.96], p=0.003). Furthermore, the proportion of vessels with CMD significantly increased (baseline; 27.1% [16/59], post-procedure; 47.5% [28/59], p=0.046) (Figure). The AMR measurement was not significantly different between SCB and PCB at baseline (p=0.53), but it was significantly higher in PCB than in SCB at post-procedure (p=0.04). Conclusion After DCB treatment, AMR significantly increased in both arms. The proportion of the vessel with CMD after procedure did not significantly change in the SCB group but increased in the PCB group. The potential mechanism of increase in AMR after DCB treatment (e.g. embolization of small crystals) may warrant further investigation.Proportion of AMR≥2.5

Prognostic Role of Functional SYNTAX Score Based on Quantitative Flow Ratio

Prognostic Role of Functional SYNTAX Score Based on Quantitative Flow Ratio

Correlation and Agreement of Quantitative Flow Ratio With Fractional Flow Reserve in Saphenous Vein Grafts.

The applicability of quantitative flow ratio (QFR), a nonhyperemic, invasive coronary angiography-derived computation of fractional flow reserve (FFR), has not been studied in coronary artery bypass grafts. We sought to explore the correlation and diagnostic agreement between QFR and FFR in saphenous vein grafts (SVGs). A total of 129 prospectively included patients (mean age 73±8 years, 84% male) with prior coronary artery bypass grafting underwent invasive coronary angiography and pressure-derived functional assessment in 150 nonoccluded SVGs. QFR dedicated angiography images of the SVGs were acquired and used for offline QFR computation. The diagnostic performance of QFR was compared with 2-dimensional quantitative coronary angiography, using FFR as a reference. A threshold of ≤0.80 was used to define functional significance. QFR was successfully computed in 140 (93%) SVGs. We found a significant correlation between QFR and FFR (r=0.72, P<0.001). FFR indicated significant disease in 43 (31%) SVGs, whereas QFR analysis showed significant lesions in 53 (38%) bypass grafts. QFR exhibited a higher sensitivity and diagnostic accuracy compared with angiographic lesion assessment (84% versus 63%, P=0.030 and 83% versus 74%, P=0.036, respectively), whereas specificity did not differ (82% versus 79%, P=0.466). Lastly, QFR demonstrated a higher area under the receiver operating curve than quantitative coronary angiography (0.90 versus 0.82, P=0.008) for the detection of FFR-defined significant vein graft disease. This study shows the potential applicability of contemporary QFR computation in venous bypass grafts with a moderate correlation and good diagnostic accuracy compared with functional assessment using FFR.

Nomogram based on virtual hyperemic pullback pressure gradients for predicting the suboptimal post-PCI QFR outcome after stent implantation.

Growing evidence shows an association between higher post-PCI quantitative flow ratios (QFR) and improved clinical prognosis, however, no models are available to predict suboptimal QFRs (< 0.91) after angiographically successful PCI. This study aims to establish a prediction nomogram for this domain. This study included 450 vessels derived from 421 consecutive patients enrolled in the PIONEER IV trial, which were randomly assigned in a 1:1 ratio to a training (N = 225) and internal validation (N = 225) set, with external validation performed in 97 vessels from 95 consecutive patients enrolled in the ASET Japan trial. LASSO regression was used for optimal feature selection, and multivariate logistic regression was subsequently utilized to construct the nomogram. The performance of the nomograms was assessed and validated by area under the receiver operating characteristics curve (AUC), calibration curves, decision curve analysis, and clinical impact curves. The nomogram was constructed incorporating a novel metric, quantitative flow ratio derived pullback pressure gradient (QFR-PPG), alongside four conventional parameters: left anterior descending artery disease, pre-procedural QFR, reference vessel diameter, and percent diameter stenosis. AUCs of the nomogram were 0.866 (95%CI:0.818-0.914), 0.784 (95% CI:0.722-0.847), and 0.781 (95% CI:0.682-0.879) in the training, internal validation and external validation sets, respectively. Bias-corrected curves revealed a strong consistency between actual observations and prediction. The risk of a suboptimal post-PCI QFR in patients after angiographically successful PCI can be effectively predicted using a nomogram incorporating five variables available pre-PCI, with its performance and clinical predictive value confirming its utility in helping clinicians with decision-making and planning revascularization. Registered on clinicaltrial.gov (NCT04923191 and NCT05117866).

Quantitative flow ratio-guided staged percutaneous coronary intervention in patients with ST-segment elevation myocardial infarction

BackgroundThe need for primary percutaneous coronary intervention (PCI) and staged PCI strategy for ST-segment elevation myocardial infarction (STEMI) with multivessel coronary disease is well documented. This study aimed to evaluate the efficiency, safety, and cost benefit of quantitative flow ratio (QFR)-guided staged PCI in patients with STEMI. MethodsWe conducted a retrospective study involving 2256 patients meeting STEMI criteria having at least one lesion (≥50 %) in non-infarct-related (NIR) arteries. These patients had undergone primary PCI for infarct-related (IR) arteries and staged PCI for NIR arteries. Patients were categorized into two groups based on the strategy guided either by QFR or quantitative coronary angiography (QCA) as determined by the clinicians during primary PCI in real-world. For patients guided by QFR, a threshold of ≤0.80 serves as the cut-off value for determining the need for PCI. We recorded the demographics, clinical data, and QFR values of none-infarct-related arteries. The efficiency, safety, and cost benefit of the QFR-guided staged PCI were evaluated. ResultsThe QCA-guided group had a higher rate of Killip II. In the QFR-guided group, there was a higher proportion of left anterior descending coronary artery lesions in infarct-related arteries. The mean QFR value of non-infarct-related (NIR) arteries remained consistent at 0.83 across both groups, irrespective of whether the measurement was taken during the primary PCI or the staged PCI phase. Among patients with QFR ≤0.8, the QFR values during staged PCI were significantly higher than that during primary PCI, with a significantly greater increase compared to patients with QFR >0.8. The proportion of staged PCI, number of stents per patient, and cost of staged PCI per patient were significantly lower in the QFR-guided group compared to the QCA-guided group. In the long-term follow-up period, there were no statistically significant differences between the two groups in terms of major adverse cardiac events and clinic visits, except for target vessel revascularization. ConclusionsQFR resulted in a reduction in the proportion of STEMI patients with multivessel coronary disease undergoing invasive coronary angiography and staged PCI. Furthermore, it decreased the incidence of target vessel revascularization (TVR) and medical costs, without increasing major adverse cardiovascular events. Our future work will focus on large multi-center perspective studies for the feasibility of QFR guided staged PCI in patients with STEMI.

Quantitative flow ratio versus fractional flow reserve for coronary revascularisation guidance (FAVOR III Europe): a multicentre, randomised, non-inferiority trial

Fractional flow reserve (FFR) or non-hyperaemic pressure ratios are recommended to assess functional relevance of intermediate coronary stenosis. Both diagnostic methods require the placement of a pressure wire in the coronary artery during invasive coronary angiography. Quantitative flow ratio (QFR) is an angiography-based computational method for the estimation of FFR that does not require the use of pressure wires. We aimed to investigate whether a QFR-based diagnostic strategy yields a non-inferior 12-month clinical outcome compared with an FFR-based strategy. FAVOR III Europe was a multicentre, randomised, open-label, non-inferiority trial comparing a QFR-based with an FFR-based diagnostic strategy for patients with intermediate coronary stenosis. Enrolment was performed in 34 centres across 11 European countries. Patients aged 18 years or older with either chronic coronary syndrome or stabilised acute coronary syndrome, and with at least one intermediate non-culprit stenosis (40-90% diameter stenosis by visual estimate; referred to here as a study lesion), were randomly assigned (1:1) to the QFR-guided or the FFR-guided group. Randomisation was done using a concealed web-based system and was stratified by diabetes and presence of a left anterior descending coronary artery study lesion. The primary endpoint was a composite of death, myocardial infarction, and unplanned revascularisation at 12 months. The predefined non-inferiority margin was 3·4% and the primary analysis was performed in the intention-to-treat population. The trial was registered with ClinicalTrials.gov (NCT03729739) and long-term follow-up is ongoing. Between Nov 6, 2018, and July 21, 2023, 2000 patients were enrolled and randomly assigned to the QFR-guided strategy (1008 patients) or the FFR-guided strategy (992 patients). The median age was 67·3 years (IQR 59·9-74·7); 1538 (76·9%) patients were male and 462 (23·1%) were female. Median follow-up time was 365 days (IQR 365-365). At 12 months, a primary endpoint event had occurred in 67 (6·7%) patients in the QFR group, and in 41 (4·2%) patients in the FFR group (hazard ratio 1·63 [95% CI 1·11-2·41]). The event proportion difference was 2·5% (90% two-sided CI 0·9-4·2). The upper limit of the 90% CI exceeded the prespecified non-inferiority margin of 3·4%. Therefore, QFR did not meet non-inferiority to FFR. A total of 18 (1·8%) patients in each group experienced an adverse procedural event, the most frequent being procedure-related myocardial infarction, which occurred in ten (1·0%) patients in the QFR group and seven (0·7%) in the FFR group. One patient in the QFR group died in relation to the index procedure. The results of the FAVOR III Europe trial do not support the use of QFR if FFR is available to guide revascularisation decisions in patients with intermediate coronary stenosis. This finding could have implications for current clinical guidelines recommending QFR for this purpose. Medis Medical Imaging Systems and Aarhus University.

Quantitative flow ratio will supplant wire-based physiological indices: pros and cons.

Quantitative flow ratio will supplant wire-based physiological indices: pros and cons.

TCT-288 Comparative Analysis of Fractional Flow Reserve Derived From Coronary Computed Tomography Angiography, Murray Law-Based Quantitative Flow Ratio and Quantitative Flow Ratio at Sequential Side Branches in Patients With Complex CAD: Insights From the FASTTRACK CABG Study

TCT-288 Comparative Analysis of Fractional Flow Reserve Derived From Coronary Computed Tomography Angiography, Murray Law-Based Quantitative Flow Ratio and Quantitative Flow Ratio at Sequential Side Branches in Patients With Complex CAD: Insights From the FASTTRACK CABG Study

Diagnostic performance of fully automatic coronary CT angiography-based quantitative flow ratio

BackgroundMurray-law based quantitative flow ratio, namely μFR, was recently validated to compute fractional flow reserve (FFR) from coronary angiographic images in the cath lab. Recently, the μFR algorithm was applied to coronary computed tomography angiography (CCTA) and a semi-automated computed μFR (CT-μFR) showed good accuracy in identifying flow-limiting coronary lesions prior to referral of patients to the cath lab. We aimed to evaluate the diagnostic accuracy of an artificial intelligence-powered method for fully automatic CCTA reconstruction and CT-μFR computation, using cath lab physiology as reference standard. MethodsThis was a post-hoc blinded analysis of the prospective CAREER trial (NCT04665817). Patients who underwent CCTA, coronary angiography including FFR within 30 days were included. Cath lab physiology standard for determining hemodynamically significant coronary stenosis was defined as FFR≤0.80, or μFR≤0.80 when FFR was not available. ResultsAutomatic CCTA reconstruction and CT-μFR computation was successfully achieved in 657 vessels from 242 patients. CT-μFR showed good correlation (r ​= ​0.62, p ​< ​0.001) and agreement (mean difference ​= ​−0.01 ​± ​0.10, p ​< ​0.001) with cath lab physiology standard. Patient-level diagnostic accuracy for CT-μFR to identify patients with hemodynamically significant stenosis was 83.0 ​% (95%CI: 78.3%–87.8 ​%), with sensitivity, specificity, positive and negative predictive value, positive and negative likelihood ratio of 84.2 ​%, 81.9 ​%, 82.1 ​%, 84.0 ​%, 4.7 and 0.2, respectively. Average analysis time for CT-μFR was 1.60 ​± ​0.34 ​min per patient. ConclusionThe fully automatic CT-μFR yielded high feasibility and good diagnostic performance in identifying patients with hemodynamically significant stenosis prior to referral of patients to the cath lab.

TCT-219 Comparative Analysis of Post-PCI Fractional Flow Reserve and Quantitative Flow Ratio in Predicting Long-term Target Vessel Failure and Hard Endpoints

TCT-219 Comparative Analysis of Post-PCI Fractional Flow Reserve and Quantitative Flow Ratio in Predicting Long-term Target Vessel Failure and Hard Endpoints