Advancements and future perspectives in coronary angiography-derived fractional flow reserve

Angiography-derived fractional flow reserve (FFR) has emerged as a non-invasive technique to assess the functional significance of coronary artery stenoses. The clinical applications of angiography-derived FFR span a wide range of scenarios, including assessing intermediate coronary lesions and guiding revascularization decisions. This review paper aims to provide an overview of angiography-derived FFR, including its principles, clinical applications, and evidence supporting its accuracy and utility. Lastly, the review discusses future directions and ongoing research in the field, including the integration of angiography-derived FFR into routine clinical practice.

Modelled impact of virtual fractional flow reserve in patients undergoing coronary angiography (VIRTU-4)

BACKGROUND

The practical application of 'virtual' (computed) fractional flow reserve (vFFR) based on invasive coronary angiogram (ICA) images is unknown. The objective of this cohort study was to investigate the potential of vFFR to guide the management of unselected patients undergoing ICA. The hypothesis was that it changes management in >10% of cases.

METHODS

vFFR was computed using the Sheffield VIRTUheart system, at five hospitals in the North of England, on 'all-comers' undergoing ICA for non-ST-elevation myocardial infarction acute coronary syndrome (ACS) and chronic coronary syndrome (CCS). The cardiologists' management plan (optimal medical therapy, percutaneous coronary intervention (PCI), coronary artery bypass surgery or 'more information required') and confidence level were recorded after ICA, and again after vFFR disclosure.

RESULTS

517 patients were screened; 320 were recruited: 208 with ACS and 112 with CCS. The median vFFR was 0.82 (0.70-0.91). vFFR disclosure did not change the mean number of significantly stenosed vessels per patient (1.16 (±0.96) visually and 1.18 (±0.92) with vFFR (p=0.79)). A change in intended management following vFFR disclosure occurred in 22% of all patients; in the ACS cohort, there was a 62% increase in the number planned for medical management, and in the CCS cohort, there was a 31% increase in the number planned for PCI. In all patients, vFFR disclosure increased physician confidence from 8 of 10 (7.33-9) to 9 of 10 (8-10) (p<0.001).

CONCLUSION

The addition of vFFR to ICA changed intended management strategy in 22% of patients, provided a detailed and specific 'all-in-one' anatomical and physiological assessment of coronary artery disease, and was accompanied by augmentation of the operator's confidence in the treatment strategy.

Diagnostic Performance of Coronary Angiography Derived Computational Fractional Flow Reserve

BACKGROUND

Computational fluid dynamics can compute fractional flow reserve (FFR) accurately. However, existing models are limited by either the intravascular hemodynamic phenomarkers that can be captured or the fidelity of geometries that can be modeled.

METHODS AND RESULTS

This study aimed to validate a new coronary angiography-based FFR framework, FFRHARVEY, and examine intravascular hemodynamics to identify new biomarkers that could augment FFR in discerning unrevascularized patients requiring intervention. A 2-center cohort was used to examine diagnostic performance of FFRHARVEY compared with reference wire-based FFR (FFRINVASIVE). Additional biomarkers, longitudinal vorticity, velocity, and wall shear stress, were evaluated for their ability to augment FFR and indicate major adverse cardiac events. A total of 160 patients with 166 lesions were investigated. FFRHARVEY was compared with FFRINVASIVE by investigators blinded to the invasive FFR results with a per-stenosis area under the curve of 0.91, positive predictive value of 90.2%, negative predictive value of 89.6%, sensitivity of 79.3%, and specificity of 95.4%. The percentage ofdiscrepancy for continuous values of FFR was 6.63%. We identified a hemodynamic phenomarker, longitudinal vorticity, as a metric indicative of major adverse cardiac events in unrevascularized gray-zone cases.

CONCLUSIONS

FFRHARVEY had high performance (area under the curve: 0.91, positive predictive value: 90.2%, negative predictive value: 89.6%) compared with FFRINVASIVE. The proposed framework provides a robust and accurate way to compute a complete set of intravascular phenomarkers, in which longitudinal vorticity was specifically shown to differentiate vessels predisposed to major adverse cardiac events.

Clinical Value of Single-Projection Angiography-Derived FFR in Noninfarct-Related Artery

BACKGROUND

The Murray law-based quantitative flow ratio (μFR) is an emerging technique that requires only 1 projection of coronary angiography with similar accuracy to quantitative flow ratio (QFR). However, it has not been validated for the evaluation of noninfarct-related artery (non-IRA) in acute myocardial infarction (AMI) settings. Therefore, our study aimed to evaluate the diagnostic accuracy of μFR and the safety of deferring non-IRA lesions with μFR >0.80 in the setting of AMI.

METHODS

μFR and QFR were analyzed for non-IRA lesions of patients with AMI enrolled in the FRAME-AMI trial (Fractional Flow Reserve Versus Angiography-Guided Strategy for Management of Non-Infarction Related Artery Stenosis in Patients With Acute Myocardial Infarction), consisting of fractional flow reserve (FFR)-guided percutaneous coronary intervention and angiography-guided percutaneous coronary intervention groups. The diagnostic accuracy of μFR was compared with QFR and FFR. Patients were classified by the non-IRA μFR value of 0.80 as a cutoff value. The primary outcome was a vessel-oriented composite outcome, a composite of cardiac death, non-IRA-related myocardial infarction, and non-IRA-related repeat revascularization.

RESULTS

μFR and QFR analyses were feasible in 443 patients (552 lesions). μFR showed acceptable correlation with FFR (R=0.777; P<0.001), comparable C-index with QFR to predict FFR ≤0.80 (μFR versus QFR: 0.926 versus 0.961, P=0.070), and shorter total analysis time (mean, 32.7 versus 186.9 s; P<0.001). Non-IRA with μFR >0.80 and deferred percutaneous coronary intervention had a significantly lower risk of vessel-oriented composite outcome than non-IRA with performed percutaneous coronary intervention (3.4% versus 10.5%; hazard ratio, 0.37 [95% CI, 0.14-0.99]; P=0.048).

CONCLUSIONS

In patients with multivessel AMI, μFR of non-IRA showed acceptable diagnostic accuracy comparable to that of QFR to predict FFR ≤0.80. Deferred non-IRA with μFR >0.80 showed a lower risk of vessel-oriented composite outcome than revascularized non-IRA.

REGISTRATION

URL: https://www.clinicaltrials.gov; Unique identifier: NCT02715518.

Consensus document on the clinical application of invasive functional coronary angiography from the Japanese Association of Cardiovascular Intervention and Therapeutics

Invasive functional coronary angiography (FCA), an angiography-derived physiological index of the functional significance of coronary obstruction, is a novel physiological assessment tool for coronary obstruction that does not require the utilization of a pressure wire. This technology enables operators to rapidly evaluate the functional relevance of coronary stenoses during and even after angiography while reducing the burden of cost and complication risks related to the pressure wire. FCA can be used for treatment decision-making for revascularization, strategy planning for percutaneous coronary intervention, and procedure optimization. Currently, various software-computing FCAs are available worldwide, with unique features in their computation algorithms and functions. With the emerging application of this novel technology in various clinical scenarios, the Japanese Association of Cardiovascular Intervention and Therapeutics task force was created to outline expert consensus on the clinical use of FCA. This consensus document advocates optimal clinical applications of FCA according to currently available evidence while summarizing the concept, history, limitations, and future perspectives of FCA along with globally available software.

Head-to-head comparison of two angiography-derived fractional flow reserve techniques in patients with high-risk acute coronary syndrome: A multicenter prospective study

BACKGROUND

FFRangio and QFR are angiography-based technologies that have been validated in patients with stable coronary artery disease. No head-to-head comparison to invasive fractional flow reserve (FFR) has been reported to date in patients with acute coronary syndromes (ACS).

METHODS

This study is a subset of a larger prospective multicenter, single-arm study that involved patients diagnosed with high-risk ACS in whom 30-70% stenosis was evaluated by FFR. FFRangio and QFR - both calculated offline by 2 different and blinded operators - were calculated and compared to FFR. The two co-primary endpoints were the comparison of the Pearson correlation coefficient between FFRangio and QFR with FFR and the comparison of their inter-observer variability.

RESULTS

Among 134 high-risk ACS screened patients, 59 patients with 84 vessels underwent FFR measurements and were included in this study. The mean FFR value was 0.82 ± 0.40 with 32 (38%) being ≤0.80. The mean FFRangio was 0.82 ± 0.20 and the mean QFR was 0.82 ± 0.30, with 27 (32%) and 25 (29%) being ≤0.80, respectively. The Pearson correlation coefficient was significantly better for FFRangio compared to QFR, with R values of 0.76 and 0.61, respectively (p = 0.01). The inter-observer agreement was also significantly better for FFRangio compared to QFR (0.86 vs 0.79, p < 0.05). FFRangio had 91% sensitivity, 100% specificity, and 96.8% accuracy, while QFR exhibited 86.4% sensitivity, 98.4% specificity, and 93.7% accuracy.

CONCLUSION

In patients with high-risk ACS, FFRangio and QFR demonstrated excellent diagnostic performance. FFRangio seems to have better correlation to invasive FFR compared to QFR but further larger validation studies are required.

Coronary Physiology as Part of a State-of-the-Art Percutaneous Coronary Intervention Strategy: Lessons from SYNTAX II and Beyond

The use of coronary physiology allows for rational decision making at the time of PCI, contributing to better patient outcomes. Yet, coronary physiology is only one aspect of optimal revascularization. State-of-the-art PCI must also consider other important aspects such as intracoronary imaging guidance and specific procedural expertise, as tested in the SYNTAX II study. In this review, we highlight the technical aspects pertaining to the use of physiology as used in that trial and offer a glimpse into the future with emerging physiologic metrics, including functional coronary angiography, which have already established themselves as useful indices to guide decision making.

Quantitative Flow Ratio to Predict Non-Target-Vessel Events Before Planned Staged Percutaneous Coronary Intervention in Patients With Acute Coronary Syndrome

BACKGROUND

The optimal time point of staged percutaneous coronary intervention (PCI) among patients with acute coronary syndrome (ACS) remains a matter of debate. Quantitative flow ratio (QFR) is a novel noninvasive method to assess the hemodynamic significance of coronary stenoses. We aimed to investigate whether QFR could refine the timing of staged PCI of non-target vessels (non-TVs) on top of clinical judgment for patients with ACS.

METHODS AND RESULTS

For this cohort study, patients with ACS from Bern University Hospital, Switzerland, scheduled to undergo out-of-hospital non-TV staged PCI were eligible. The primary end point was the composite of non-TV myocardial infarction and urgent unplanned non-TV PCI before planned staged PCI. The association between lowest QFR per patient measured in the non-TV (from index angiogram) and the primary end point was assessed using multivariable adjusted Cox proportional hazards regressions with QFR included as linear or penalized spline (nonlinear) term. QFR was measured in 1093 of 1432 patients with ACS scheduled to undergo non-TV staged PCI. Median time to staged PCI was 28 days. The primary end point occurred in 5% of the patients. In multivariable analysis (1018 patients), there was no independent association between non-TV QFR and the primary end point (hazard ratio, 0.87 [95% CI, 0.69-1.05] per 0.1 increase; P=0.125; nonlinear P=0.648).

CONCLUSIONS

In selected patients with ACS scheduled to undergo staged PCI at a median of 4 weeks after index PCI, QFR did not emerge as an independent predictor of non-TV events before planned staged PCI. Thus, this study does not provide conceptual evidence that QFR is helpful to refine the timing of staged PCI on top of clinical judgment.

REGISTRATION

URL: https://www.clinicaltrials.gov; Unique identifier: NCT02241291.

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.

Diagnostic performance of angiography-derived fractional flow reserve analysis based on bifurcation fractal law for assessing hemodynamic significance of coronary stenosis

OBJECTIVES

Blood flow into the side branch affects the calculation of coronary angiography-derived fractional flow reserve (FFR), called Angio-FFR. Neglecting or improperly compensating for the side branch flow may decrease the diagnostic accuracy of Angio-FFR. This study aims to evaluate the diagnostic accuracy of a novel Angio-FFR analysis that considers the side branch flow based on the bifurcation fractal law.

METHODS

A one-dimensional reduced-order model based on the vessel segment was used to perform Angio-FFR analysis. The main epicardial coronary artery was divided into several segments according to the bifurcation nodes. Side branch flow was quantified using the bifurcation fractal law to correct the blood flow in each vessel segment. In order to verify the diagnostic performance of our Angio-FFR analysis, two other computational methods were taken as control groups: (i) FFR_s: FFR calculated by delineating the coronary artery tree to consider side branch flow, (ii) FFR_n: FFR calculated by just delineating the main epicardial coronary artery and neglecting the side branch flow.

RESULTS

The analysis of 159 vessels from 119 patients showed that our Anio-FFR calculation method had comparable diagnostic accuracy to FFR_s and provided significantly higher diagnostic accuracy than that of FFR_n. In addition, using invasive FFR as a reference, the Pearson correlation coefficients of Angio-FFR and FFRs were 0.92 and 0.91, respectively, while that of FFR_n was only 0.85.

CONCLUSIONS

Our Angio-FFR analysis has demonstrated good diagnostic performance in assessing the hemodynamic significance of coronary stenosis by using the bifurcation fractal law to compensate for side branch flow.

CLINICAL RELEVANCE STATEMENT

Bifurcation fractal law can be used to compensate for side branch flow during the Angio-FFR calculation of the main epicardial vessel. Compensating for side branch flow can improve the ability of Angio-FFR to diagnose stenosis functional severity.

KEY POINTS

• The bifurcation fractal law could accurately estimate the blood flow from the proximal main vessel into the main branch, thus compensating for the side branch flow. • Angiography-derived FFR based on the bifurcation fractal law is feasible to evaluate the target diseased coronary artery without delineating the side branch.

Clinical Value of Computational Angiography-derived Fractional Flow Reserve in Stable Coronary Artery Disease

The utilization of FFR remains low. Our study evaluated the per-vessel prognostic value of computational pressure-flow dynamics-derived FFR (caFFR) among patients with stable coronary artery disease. A total of 3329 vessels from 1308 patients were included and analysed. They were stratified into ischaemic (caFFR ≤ 0.8) and non-ischaemic (caFFR > 0.8) cohorts, and the associations between PCI and outcomes were evaluated. The third cohort comprised all included vessels, and the associations between treatment adherent-to-caFFR (PCI in vessels with caFFR ≤ 0.8 and no PCI in vessels with caFFR > 0.8) and outcomes were evaluated. The primary outcome was VOCE, defined as a composite of vessel-related cardiovascular mortality, non-fatal myocardial infarction, and repeat revascularization. PCI was associated with a lower 3-year risk of VOCE in the ischaemic cohort (HR, 0.44; 95% CI, 0.26-0.74; P = 0.002) but not in the non-ischaemic cohort. The risk of VOCE was lower in the adherent-to-caFFR group (n = 2649) (HR, 0.69; 95% CI, 0.48-0.98; P = 0.039). A novel index that uses coronary angiography images to estimate FFR may have substantial clinical value in guiding management among patients with stable coronary artery disease.

Functional Assessment of Coronary Artery Stenosis from Coronary Angiography and Computed Tomography: Angio-FFR vs. CT-FFR

This study was designed to compare the diagnostic performance of angio-FFR and CT-FFR for detecting hemodynamically significant coronary stenosis. Angio-FFR and CT-FFR were measured in 110 patients (139 vessels) with stable coronary disease using invasive FFR as the reference standard. On per-patient basis, angio-FFR was highly correlated with FFR (r =0.78, p <0.001), while the correlation was moderate between CT-FFR and FFR (r =0.68, p <0.001). Diagnostic accuracy, sensitivity, and specificity for angio-FFR were 94.6%, 91.4%, and 96.0%, respectively; and those of CT-FFR were 91.8%, 91.4%, and 92%, respectively. Bland-Altman analysis showed that angio-FFR had a larger average difference and a smaller root mean squared deviation than CT-FFR compared with FFR (-0.014±0.056 vs. 0.0003±0.072). Angio-FFR had a slightly higher AUC than that of CT-FFR (0.946 vs. 0.935, p =0.750). Angio-FFR and CT-FFR computed from coronary images could be accurate and efficient computational tools for detecting lesion-specific ischemia of coronary artery stenosis. Angio-FFR and CT-FFR calculated based on the two types of images can both accurately diagnose functional ischemia of coronary stenosis. CT-FFR can act as a gatekeeper to the catheter room, assisting doctors in determining whether patients need to be screened by coronary angiography. Angio-FFR can be used in the catheter room to determine the functional significant stenosis for helping decision-making in revascularization.

Impact of alirocumab on plaque regression and haemodynamics of non-culprit arteries in patients with acute myocardial infarction: a prespecified substudy of the PACMAN-AMI trial

BACKGROUND

Treatment with proprotein convertase subtilisin/kexin type 9 (PCSK9) inhibitors on top of statins leads to plaque regression and stabilisation. The effects of PCSK9 inhibitors on coronary physiology and angiographic diameter stenosis (DS%) are unknown.

AIMS

This study aimed to investigate the effects of the PCSK9 inhibitor alirocumab on coronary haemodynamics as assessed by quantitative flow ratio (QFR) and DS% by three-dimensional quantitative coronary angiography (3D-QCA) in non-infarct-related arteries (non-IRA) among acute myocardial infarction (AMI) patients.

METHODS

This was a prespecified substudy of the randomised controlled PACMAN-AMI trial, comparing alirocumab versus placebo on top of rosuvastatin. QFR and 3D-QCA were assessed at baseline and 1 year in any non-IRA ≥2.0 mm and 3D-QCA DS% >25%. The prespecified primary endpoint was the number of patients with a mean QFR increase at 1 year, and the secondary endpoint was the change in 3D-QCA DS%.

RESULTS

Of 300 enrolled patients, 265 had serial follow-up, of which 193 underwent serial QFR/3D-QCA analysis in 282 non-IRA. At 1 year, QFR increased in 50/94 (53.2%) patients with alirocumab versus 40/99 (40.4%) with placebo (Δ12.8%; odds ratio 1.7, 95% confidence interval [CI]: 0.9 to 3.0; p=0.076). DS% decreased by 1.03±7.28% with alirocumab and increased by 1.70±8.27% with placebo (Δ-2.50%, 95% CI: -4.43 to -0.57; p=0.011).

CONCLUSIONS

Treatment of AMI patients with alirocumab versus placebo for 1 year resulted in a significant regression in angiographic DS%, whereas no overall improvement of coronary haemodynamics was observed.

CLINICALTRIALS

gov: NCT03067844.

Danish study of Non-Invasive Testing in Coronary Artery Disease 3 (Dan-NICAD 3): study design of a controlled study on optimal diagnostic strategy

INTRODUCTION

Current guideline recommend functional imaging for myocardial ischaemia if coronary CT angiography (CTA) has shown coronary artery disease (CAD) of uncertain functional significance. However, diagnostic accuracy of selective myocardial perfusion imaging after coronary CTA is currently unclear. The Danish study of Non-Invasive testing in Coronary Artery Disease 3 trial is designed to evaluate head to head the diagnostic accuracy of myocardial perfusion imaging with positron emission tomography (PET) using the tracers ⁸²Rubidium (⁸²Rb-PET) compared with oxygen-15 labelled water PET (¹⁵O-water-PET) in patients with symptoms of obstructive CAD and a coronary CT scan with suspected obstructive CAD.

METHODS AND ANALYSIS

This prospective, multicentre, cross-sectional study will include approximately 1000 symptomatic patients without previous CAD. Patients are included after referral to coronary CTA. All patients undergo a structured interview and blood is sampled for genetic and proteomic analysis and a coronary CTA. Patients with possible obstructive CAD at coronary CTA are examined with both ⁸²Rb-PET, ¹⁵O-water-PET and invasive coronary angiography with three-vessel fractional flow reserve and thermodilution measurements of coronary flow reserve. After enrolment, patients are followed with Seattle Angina Questionnaires and follow-up PET scans in patients with an initially abnormal PET scan and for cardiovascular events in 10 years.

ETHICS AND DISSEMINATION

Ethical approval was obtained from Danish regional committee on health research ethics. Written informed consent will be provided by all study participants. Results of this study will be disseminated via articles in international peer-reviewed journal.

TRIAL REGISTRATION NUMBER

NCT04707859.

Coronary Angiography Upgraded by Imaging Post-Processing: Present and Future Directions

Advances in computer technology and image processing now allow us to obtain from angiographic images a large variety of information on coronary physiology without the use of a guide-wire as a diagnostic information equivalent to FFR and iFR but also information allowing for the performance of a real virtual percutaneous coronary intervention (PCI) and finally the ability to obtain information to optimize the results of PCI. With specific software, it is now possible to have a real upgrading of invasive coronary angiography. In this review, we present the different advances in this field and discuss the future perspectives offered by this technology.

Anonymous Comparison of Various Angiography-Derived Fractional Flow Reserve Software With Pressure-Derived Physiological Assessment

BACKGROUND

Software to compute angiography-derived fractional flow reserve (angio-FFR) have been validated against pressure wire-derived fractional flow reserve (PW-FFR) with an area under the receiver-operating characteristic curve (AUC) of 0.93 to 0.97.

OBJECTIVES

The aim of this study was to investigate diagnostic accuracies of 5 angio-FFR software/methods by an independent core lab in a prospective cohort of 390 vessels with carefully documented sites of PW-FFR and pressure wire-derived instantaneous wave-free ratio.

METHODS

One "matcher investigator" colocalized on angiography the sites of pressure wire measurement with angio-FFR measurements and provided the same 2 optimal angiographic views and frame selection to independent analysts who were blinded to invasive physiological results and results from other software. The results were anonymized and randomly presented. The AUC of each angio-FFR was compared with 2-dimensional quantitative coronary angiography (QCA) percent diameter stenosis (%DS) using a 2-tailed paired comparison of AUC.

RESULTS

All 5 software/methods yielded a high proportion of analyzable vessels (A: 100%, B: 100%, C: 92.1%, D: 99.5%, and E: 92.1%). The AUCs for predicting fractional flow reserve ≤0.8 for software A, B, C, D, E, and 2-dimensional QCA %DS were 0.75, 0.74, 0.74, 0.73, 0.73, and 0.65, respectively. The AUC for each angio-FFR was significantly greater than that for 2-dimensional QCA %DS.

CONCLUSIONS

This head-to-head comparison by an independent core lab demonstrated that the diagnostic accuracy of various angio-FFR software for predicting PW-FFR ≤0.80 was useful, with a higher discrimination compared with 2-dimensional QCA %DS; however, it did not reach the diagnostic accuracy previously reported in validation studies of various vendors. Therefore, the intrinsic clinical value of "angiography-derived fractional flow reserve" requires confirmation in large clinical trials.

Quantitative flow ratio versus fractional flow reserve for guiding percutaneous coronary intervention: design and rationale of the randomised FAVOR III Europe Japan trial

Quantitative flow ratio (QFR) is a computation of fractional flow reserve (FFR) based on invasive coronary angiographic images. Calculating QFR is less invasive than measuring FFR and may be associated with lower costs. Current evidence supports the call for an adequately powered randomised comparison of QFR and FFR for the evaluation of intermediate coronary stenosis. The aim of the FAVOR III Europe Japan trial is to investigate if a QFR-based diagnostic strategy yields a non-inferior 12-month clinical outcome compared with a standard FFR-guided strategy in the evaluation of patients with intermediary coronary stenosis. FAVOR III Europe Japan is an investigator-initiated, randomised, clinical outcome, non-inferiority trial scheduled to randomise 2,000 patients with either 1) stable angina pectoris and intermediate coronary stenosis, or 2) indications for functional assessment of at least 1 non-culprit lesion after acute myocardial infarction. Up to 40 international centres will randomise patients to either a QFR-based or a standard FFR-based diagnostic strategy. The primary endpoint of major adverse cardiovascular events is a composite of all-cause mortality, any myocardial infarction, and any unplanned coronary revascularisation at 12 months. QFR could emerge as an adenosine- and wire-free alternative to FFR, making the functional evaluation of intermediary coronary stenosis less invasive and more cost-effective.

Validity and Diagnostic Performance of Computing Fractional Flow Reserve From 2-Dimensional Coronary Angiography Images

BACKGROUND

Measurement of fractional flow reserve (FFR) is the gold standard for determining the physiologic significance of coronary artery stenosis, but newer software programs can calculate the FFR from 2-dimensional angiography images.

METHODS

A retrospective analysis was conducted using the records of patients with intermediate coronary stenoses who had undergone adenosine FFR (aFFR). To calculate the computed FFR, a software program used simulated coronary blood flow using computational geometry constructed using at least 2 patient-specific angiographic images. Two cardiologists reviewed the angiograms and determined the computational FFR independently. Intraobserver variability was measured using κ analysis and the intraclass correlation coefficient. The correlation coefficient and Bland-Altman plots were used to assess the agreement between the calculated FFR and the aFFR.

RESULTS

A total of 146 patients were included, with 95 men and 51 women, with a mean (SD) age of 61.1 (9.5) y. The mean (SD) aFFR was 0.847 (0.072), and 41 patients (27.0%) had an aFFR of 0.80 or less. There was a strong intraobserver correlation between the computational FFRs (r = 0.808; P < .001; κ = 0.806; P < .001). There was also a strong correlation between aFFR and computational FFR (r = 0.820; P < .001) and good agreement on the Bland-Altman plot. The computational FFR had a high sensitivity (95.1%) and specificity (90.1%) for detecting an aFFR of 0.80 or less.

CONCLUSION

A novel software program provides a feasible method of calculating FFR from coronary angiography images without resorting to pharmacologically induced hyperemia.

Coronary Physiology as Part of a State-of-the-Art Percutaneous Coronary Intervention Strategy: Lessons from SYNTAX II and Beyond

The use of coronary physiology allows for rational decision making at the time of PCI, contributing to better patient outcomes. Yet, coronary physiology is only one aspect of optimal revascularization. State-of-the-art PCI must also consider other important aspects such as intracoronary imaging guidance and specific procedural expertise, as tested in the SYNTAX II study. In this review, we highlight the technical aspects pertaining to the use of physiology as used in that trial and offer a glimpse into the future with emerging physiologic metrics, including functional coronary angiography, which have already established themselves as useful indices to guide decision making.

Is it the Time to Move Towards Coronary Computed Tomography Angiography-Derived Fractional Flow Reserve Guided Percutaneous Coronary Intervention? The Pros and Cons

Coronary artery disease is the leading cause of mortality worldwide. Diagnosis is conventionally performed by direct visualization of the arteries by invasive coronary angiography (ICA), which has inherent limitations and risks. Measurement of fractional flow reserve (FFR) has been suggested for a more accurate assessment of ischemia in the coronary artery with high accuracy for determining the severity and decision on the necessity of intervention. Nevertheless, invasive coronary angiography-derived fractional flow reserve (ICA-FFR) is currently used in less than one-third of clinical practices because of the invasive nature of ICA and the need for additional equipment and experience, as well as the cost and extra time needed for the procedure. Recent technical advances have moved towards non-invasive high-quality imaging modalities, such as magnetic resonance, single-photon emission computed tomography, and coronary computed tomography (CT) scan; however, none had a definitive modality to confirm hemodynamically significant coronary artery stenosis. Coronary computed tomography angiography (CCTA) can provide accurate anatomic and hemodynamic data about the coronary lesion, especially calculating fractional flow reserve derived from CCTA (CCTA-FFR). Although growing evidence has been published regarding CCTA-FFR results being comparable to ICA-FFR, CCTA-FFR has not yet replaced the invasive conventional angiography, pending additional studies to validate the advantages and disadvantages of each diagnostic method. Furthermore, it has to be identified whether revascularization of a stenotic lesion is plausible based on CCTA-FFR and if the therapeutic plan can be determined safely and accurately without confirmation from invasive methods. Therefore, in the present review, we will outline the pros and cons of using CCTA-FFR vs. ICA-FFR regarding diagnostic accuracy and treatment decision-making.

The impact of deep learning reconstruction on image quality and coronary CT angiography-derived fractional flow reserve values

OBJECTIVES

To explore the impact of deep learning reconstruction (DLR) on image quality and machine learning-based coronary CT angiography (CTA)-derived fractional flow reserve (CT-FFR_ML) values.

METHODS

Thirty-three consecutive patients with known or suspected coronary artery disease who underwent coronary CTA and subsequent invasive coronary angiography were enrolled. DLR was compared with filtered back projection (FBP), statistical-based iterative reconstruction (SBIR), model-based iterative reconstruction (MBIR) Cardiac, and MBIR Cardiac sharp for objective image qualities of coronary CTA. Invasive fractional flow reserve (FFR) and quantitative flow ratio (QFR) were used as the reference standards. The diagnostic performances of different reconstruction approach-based CT-FFR_ML were calculated.

RESULTS

A total of 182 lesions in 33 patients were enrolled for analysis. The image quality of DLR was superior to the others. There were no significant differences in the CT-FFR_ML values among these five approaches (all p > 0.05). Of the 182 lesions, 17 had invasive FFR results, and 70 had QFR results. Using FFR as a reference, MBIR Cardiac, MBIR Cardiac sharp, and DLR achieved equal diagnostic performance, slightly higher than the other reconstruction approaches (MBIR Cardiac, MBIR Cardiac sharp, and DLR: AUC = 0.82, FBP and AIDR: AUC = 0.78, all p > 0.05). Using QFR as a reference, the AUCs of FBP, SBIR, MBIR Cardiac, MBIR Cardiac sharp, and DLR were 0.83, 0.81, 0.86, 0.84, and 0.83, respectively (all p > 0.05).

CONCLUSIONS

Our study showed that the DLR algorithm improved image quality, but there were no significant differences in the CT-FFR_ML values and diagnostic performance among different reconstruction approaches.

KEY POINTS

• Deep learning-based image reconstruction (DLR) improves the image quality of coronary CTA. • CT-FFR_ML values and diagnostic performance of DLR revealed no significant differences compared to other reconstruction approaches.

Coronary physiology in the catheterisation laboratory: an A to Z practical guide

Coronary revascularisation, either percutaneous or surgical, aims to improve coronary flow and relieve myocardial ischaemia. The decision-making process in patients with coronary artery disease (CAD) remains largely based on invasive coronary angiography (ICA), even though until recently ICA could not assess the functional significance of coronary artery stenoses. Invasive wire-based approaches for physiological evaluations were developed to properly assess the ischaemic relevance of epicardial CAD. Fractional flow reserve (FFR) and later, instantaneous wave-free ratio (iFR), were shown to improve clinical outcomes in several patient subsets when used for coronary revascularisation guidance or deferral and for procedural optimisation of percutaneous coronary intervention (PCI) results. Despite accumulating evidence and positive guideline recommendations, the adoption of invasive physiology has remained quite low, mainly due to technical and economic issues as well as to operator-resistance to change. Coronary image-based computational physiology has been recently developed, with promising results in terms of accuracy and a reduction in computational time, costs, radiation exposure and risks for the patient. Lastly, the integration of intracoronary imaging and physiology allows for individualised PCI treatment, aiming at complete relief of ischaemia through optimised morpho-functional immediate procedural results. Instead of a conventional state-of-the-art review, this A to Z dictionary attempts to provide a practical guide for the application of coronary physiology in the catheterisation laboratory, exploring several methods, their pitfalls, and useful tips and tricks.

Incorporating clinical parameters to improve the accuracy of angiography-derived computed fractional flow reserve. EUROPEAN HEART JOURNAL. DIGITAL HEALTH 2022;3:481-488. [PMID: 36712154 PMCID: PMC9707918 DOI: 10.1093/ehjdh/ztac045] [Citation(s) in RCA: 0] [Impact Index Per Article: 0]

Aims

Angiography-derived fractional flow reserve (angio-FFR) permits physiological lesion assessment without the need for an invasive pressure wire or induction of hyperaemia. However, accuracy is limited by assumptions made when defining the distal boundary, namely coronary microvascular resistance (CMVR). We sought to determine whether machine learning (ML) techniques could provide a patient-specific estimate of CMVR and therefore improve the accuracy of angio-FFR.

Methods and results

Patients with chronic coronary syndromes underwent coronary angiography with FFR assessment. Vessel-specific CMVR was computed using a three-dimensional computational fluid dynamics simulation with invasively measured proximal and distal pressures applied as boundary conditions. Predictive models were created using non-linear autoregressive moving average with exogenous input (NARMAX) modelling with computed CMVR as the dependent variable. Angio-FFR (VIRTUheart™) was computed using previously described methods. Three simulations were run: using a generic CMVR value (Model A); using ML-predicted CMVR based upon simple clinical data (Model B); and using ML-predicted CMVR also incorporating echocardiographic data (Model C). The diagnostic (FFR ≤ or >0.80) and absolute accuracies of these models were compared. Eighty-four patients underwent coronary angiography with FFR assessment in 157 vessels. The mean measured FFR was 0.79 (±0.15). The diagnostic and absolute accuracies of each personalized model were: (A) 73% and ±0.10; (B) 81% and ±0.07; and (C) 89% and ±0.05, P < 0.001.

Conclusion

The accuracy of angio-FFR was dependent in part upon CMVR estimation. Personalization of CMVR from standard clinical data resulted in a significant reduction in angio-FFR error.

Angiography derived assessment of the coronary microcirculation: is it ready for prime time?

INTRODUCTION

Non-obstructive coronary arteries (NOCA) are present in 39.7% to 62.4% of patients who undergo elective angiography. Coronary microcirculation (<400 µm) is not visible on angiography therefore functional assessment, invasive or non-invasive plays a prior role to help provide a more personalized diagnosis of angina.

AREA COVERED

In this review, we revise the pathophysiology, clinical importance and invasive assessment of the coronary microcirculation, and discuss angiography-derived indices of microvascular resistance. A comprehensive literature review over four decades is also undertaken.

EXPERT OPINION

The coronary microvasculature plays an important role in flow autoregulation and metabolic regulation. Invasive assessment of microvascular resistance is a validated modality with independent prognostic value, nevertheless, its routine application is hampered by the requirement of intravascular instrumentation and hyperaemic agents. The angiography-derived index of microvascular resistance has emerged as a promising surrogate in pilot studies, however, more data are needed to validate and compare the diagnostic and prognostic accuracy of different equations as well as to illustrate the relationship between angiography-derived parameters for epicardial coronary arteries and those for the microvasculature.

Prognosis and Medical Cost of Measuring Fractional Flow Reserve in Percutaneous Coronary Intervention

Background

There are limited data regarding comparative prognosis and medical cost between fractional flow reserve (FFR)-based and angiography-based percutaneous coronary intervention (PCI) among revascularized patients.

Objectives

This study evaluates prognosis and medical cost of FFR use in revascularized patients by PCI.

Methods

Using the National Health Insurance Service database, stable or unstable angina patients who underwent PCI from 2011 to 2017 were evaluated. Eligible patients were divided into 2 groups according to use of FFR in PCI. Primary outcome was a composite of all-cause death or spontaneous myocardial infarction (MI). Secondary outcomes included individual components of the primary outcome, unplanned revascularization, and medical costs.

Results

Among 134,613 eligible patients, PCI was performed based on angiography (n = 129,497) and FFR (n = 5,116). During the study period, both the annual number and proportion of use of FFR in PCI increased (all P for trend <0.001). The FFR group showed significantly lower risk of the primary outcome (7.0% vs 9.5%; P < 0.001), all-cause death (5.8% vs 7.7%; P = 0.001), and spontaneous MI (1.6% vs 2.2%; P = 0.022) than the angiography group. Although the FFR group showed higher medical cost during index admission than angiography group (median: $6,265.10 vs $5,385.60; P < 0.001), cumulative medical cost after index admission was significantly lower ($2,696.50 vs. $3,142.10; P < 0.001).

Conclusions

Use of FFR in PCI in stable or unstable angina patients showed significantly lower risk of all-cause death and spontaneous MI compared to angiography-based PCI. Although the FFR group had higher initial medical cost than the angiography group, cumulative medical cost after index admission was significantly lower.

The Use of Digital Coronary Phantoms for the Validation of Arterial Geometry Reconstruction and Computation of Virtual FFR

We present computational fluid dynamics (CFD) results of virtual fractional flow reserve (vFFR) calculations, performed on reconstructed arterial geometries derived from a digital phantom (DP). The latter provides a convenient and parsimonious description of the main vessels of the left and right coronary arterial trees, which, crucially, is CFD-compatible. Using our DP, we investigate the reconstruction error in what we deem to be the most relevant way—by evaluating the change in the computed value of vFFR, which results from varying (within representative clinical bounds) the selection of the virtual angiogram pair (defined by their viewing angles) used to segment the artery, the eccentricity and severity of the stenosis, and thereby, the CFD simulation’s luminal boundary. The DP is used to quantify reconstruction and computed haemodynamic error within the VIRTUheartTM software suite. However, our method and the associated digital phantom tool are readily transferable to equivalent, clinically oriented workflows. While we are able to conclude that error within the VIRTUheartTM workflow is suitably controlled, the principal outcomes of the work reported here are the demonstration and provision of a practical tool along with an exemplar methodology for evaluating error in a coronary segmentation process.

Computational Pressure-Fluid Dynamics Applied to Index of Microcirculatory Resistance, Predicting the Prognosis of Drug-Coated Balloons Compared With Drug-Eluting Stents in STEMI Patients

Background: The impairment of microvascular injury on prognosis has increasingly drawn extensive awareness along with the high morbidity and mortality of ST-segment elevation myocardial infarction (STEMI) over recent years. The prognostic significance of computational pressure-fluid dynamics applied to index of microcirculatory resistance, derived from coronary angiography (CPFD-caIMR) in microvascular injury evaluation of STEMI patients remained inconclusive.

Methods: A total of 213 patients who met the inclusion criteria were selected retrospectively from 1003 STEMI patients from February 2018 to February 2020. Propensity score matching (PSM) was thereafter finished. CPFD-caIMR of all patients was obtained off-line using the software (FlashAngio, Rainmed Ltd., Suzhou, China) after PPCI. The primary endpoint was to compare the CPFD-caIMR and the incidence of major adverse cardiovascular events (MACEs) between drug-coated balloons (DCB) and drug-eluting stents (DES) groups. The correlation between CPFD-caIMR and MACEs was analyzed, and the prognosis of patients with STEMI was evaluated by CPFD-caIMR by multivariate regression analysis.

Results: Totally 213 STEMI patients with successful primary percutaneous coronary intervention (PPCI) were included, of whom 84 patients accepted DCB and 129 patients accepted DES respectively. Baseline characteristics and CPFD-caIMR were comparable between DCB and DES groups after PSM (62 patients in each group). CPFD-caIMR was not significantly different between two groups (DES vs. DCB: mean difference: 2.26, 95% CI -4.05 to 8.57, p = 0.45), and so was it when re-grouped by whether CPFD-caIMR > 40U or not (DES vs. DCB: 34.17% vs. 27.16%, p = 0.29). After a follow-up of 1 year, more MACEs occurred in DES group than DCB group (relative risk: 2.50, 95% CI 1.04 to 6.02, p = 0.04). The predictors of MACEs by multi-variate analysis found that, only time from symptom to balloon (p = 0.03) and time from door to balloon (p < 0.01) were independent predictors of MACEs, independent of treatment with DCB or DES intervention. Furthermore, CPFD-caIMR > 40U became an independent predictor of the combined events including cardiovascular deaths or heart failure readmission irrespective of PSM (odds ratio: 4.07, 95% CI: 1.06 to 7.66, p = 0.04).

Conclusion: CPFD-caIMR was a promising method for prognosis, which can predict CV death or heart failure readmission in STEMI patients. DCB was a possible strategy in PPCI of STEMI patients, not inferior to DES based on microvascular injury evaluated by CPFD-caIMR.

Three-dimensional QCA-based vessel fractional flow reserve (vFFR) in Heart Team decision-making: a multicentre, retrospective, cohort study

OBJECTIVES

To evaluate the feasibility of three-vessel three-dimensional (3D) quantitative coronary angiography (QCA)-based fractional flow reserve (FFR) computation in patients discussed within the Heart Team in whom the treatment decision was based on angiography alone, and to evaluate the concordance between 3D QCA-based vessel FFR (vFFR)-confirmed functional lesion significance and revascularisation strategy as proposed by the Heart Team.

DESIGN

Retrospective, cohort.

SETTING

3D QCA-based FFR indices have not yet been evaluated in the context of Heart Team decision-making; consecutive patients from six institutions were screened for eligibility and three-vessel vFFR was computed by blinded analysts.

PARTICIPANTS

Consecutive patients with chronic coronary syndrome or unstable angina referred for Heart Team consultation. Exclusion criteria involved: presentation with acute myocardial infarction (MI), significant valve disease, left ventricle ejection fraction <30%, inadequate quality of angiogram precluding vFFR computation in all three epicardial coronary arteries (ie, absence of a minimum of two angiographic projections with views of at least 30° apart, substantial foreshortening/overlap of the vessel, poor contrast medium injection, ostial lesions, chronic total occlusions).

PRIMARY AND SECONDARY OUTCOME MEASURES

Discordance between vFFR-confirmed lesion significance and revascularisation was assessed as the primary outcome measure. Rates of major adverse cardiac events (MACE) defined as cardiac death, MI and clinically driven revascularisation were reported.

RESULTS

Of a total of 1003 patients were screened for eligibility, 416 patients (age 65.6±10.6, 71.2% male, 53% stable angina) were included. The most important reason for screening failure was insufficient quality of the angiogram (43%). Discordance between vFFR confirmed lesion significance and revascularisation was found in 124/416 patients (29.8%) corresponding to 149 vessels (46/149 vessels (30.9%) were reclassified as significant and 103/149 vessels (69.1%) as non-significant by vFFR). Over a median of 962 days, the cumulative incidence of MACE was 29.7% versus 18.5% in discordant versus concordant patients (p=0.031).

CONCLUSIONS

vFFR computation is feasible in around 40% of the patients referred for Heart Team discussion, a limitation that is mostly based on insufficient quality of the angiogram. Three vessel vFFR screening indicated discordance between vFFR confirmed lesion significance and revascularisation in 29.8% of the patients.

Angiography-derived physiology guidance vs usual care in an All-comers PCI population treated with the healing-targeted supreme stent and Ticagrelor monotherapy: PIONEER IV trial design

BACKGROUND

Current ESC guidelines recommend the use of intra-coronary pressure guidewires for functional assessment of intermediate-grade coronary stenoses. Angiography-derived quantitative flow ratio (QFR) is a novel method of assessing these stenoses, and guiding percutaneous coronary intervention (PCI).

METHODS/DESIGN

The PIONEER IV trial is a prospective, all-comers, multi-center trial, which will randomize 2,540 patients in a 1:1 ratio to PCI guided by angiography-derived physiology or usual care, with unrestricted use in both arms of the Healing-Targeted Supreme sirolimus-eluting stent (HT Supreme). The stent's fast, biologically healthy, and robust endothelial coverage allows for short dual-antiplatelet therapy (DAPT); hence the antiplatelet regimen of choice is 1-month DAPT, followed by ticagrelor monotherapy. In the angiography-derived physiology guided arm, lesions will be functionally assessed using on-line QFR, with stenting indicated in lesions with a QFR ≤0.80. Post-stenting, QFR will be repeated in the stented vessel(s), with post-dilatation or additional stenting recommended if the QFR<0.91 distal to the stent, or if the delta QFR (across the stent) is >0.05. Usual care PCI is performed according to standard clinical practice. The primary endpoint is a non-inferiority comparison of the patient-oriented composite endpoint (POCE) of all-cause death, any stroke, any myocardial infarction, or any clinically, and physiologically driven revascularization with a non-inferiority risk-difference margin of 3.2%, at 1-year post-procedure. Clinical follow-up will be up to 3 years.

SUMMARY

The PIONEER IV trial aims to demonstrate non-inferiority of QFR-guided PCI to usual care PCI with respect to POCE at 1-year in patients treated with HT Supreme stents and ticagrelor monotherapy.

CLINICAL TRIAL REGISTRATION

ClinicalTrials.gov UNIQUE IDENTIFIER: NCT04923191 CLASSIFICATIONS: Interventional Cardiology.

Diagnostic Accuracy of Coronary Angiography-Based Vessel Fractional Flow Reserve (vFFR) Virtual Stenting

3D coronary angiography-based vessel fractional flow reserve (vFFR) proved to be an accurate diagnostic alternative to invasively measured pressure wire based fractional flow reserve (FFR). The ability to compute post-PCI vFFR using pre-PCI vFFR virtual stent analysis is unknown. We aimed to assess the feasibility and diagnostic accuracy of pre-PCI vFFR virtual stenting analysis (residual vFFR) with post-PCI FFR as a reference. This is an observational, single-center retrospective cohort study including consecutive patients from the FFR-SEARCH registry. We blindly calculated residual vFFR from pre-PCI angiograms and compared them to invasive pressure-wire based post-PCI FFR. Inclusion criteria involved presentation with either stable or unstable angina or non-ST elevation myocardial infarction (NSTEMI), ≥1 significant stenosis in one of the epicardial coronary arteries (percentage diameter stenosis of >70% by QCA or hemodynamically relevant stenosis with FFR ≤0.80) and pre procedural angiograms eligible for vFFR analysis. Exclusion criteria comprised patients with ST elevation myocardial infarction (STEMI), coronary bypass grafts, cardiogenic shock or severe hemodynamic instability. Eighty-one pre-PCI residual vFFR measurements were compared to post-PCI FFR and post-PCI vFFR measurements. Mean residual vFFR was 0.91 ± 0.06, mean post-PCI FFR 0.91 ± 0.06 and mean post-PCI vFFR was 0.92 ± 0.05. Residual vFFR showed a high linear correlation (r = 0.84) and good agreement (mean difference (95% confidence interval): 0.005 (−0.002−0.012)) with post-PCI FFR, as well as with post-PCI-vFFR (r = 0.77, mean difference −0.007 (−0.015−0.0003)). Residual vFFR showed good accuracy in the identification of lesions with post-PCI FFR < 0.90 (sensitivity 94%, specificity 71%, area under the curve (AUC) 0.93 (95% CI: 0.86−0.99), p < 0.001). Virtual stenting using vFFR provided an accurate estimation of post-PCI FFR and post-PCI vFFR. Further studies are needed to prospectively validate a vFFR-guided PCI strategy.

Fractional Flow Reserve: Patient Selection and Perspectives

The aim of this review was to discuss the current practice and patient selection for invasive FFR, new techniques to estimate invasive FFR and future of coronary physiology tests. We elaborate on the indication and application of FFR and on the contraindications and concerns in certain patient populations.

Diagnostic Value of Angiography-Derived IMR for Coronary Microcirculation and Its Prognostic Implication After PCI

Background: Angiography-derived index of microcirculatory resistance (angio-IMR) is an emerging pressure-wire-free index to assess coronary microvascular function, but its diagnostic and prognostic value remains to be elucidated.

Methods and Results: The study population consisted of three independent cohorts. The internal diagnostic cohort enrolled 53 patients with available hyperemic microcirculatory resistance (HMR) calculated from myocardial blood flow and pressure. The external diagnostic cohort included 35 ischemia and no obstructive coronary artery disease (INOCA) patients and 45 controls. The prognostic cohort included 138 coronary artery disease (CAD) patients who received PCI. Angio-IMR was calculated after the estimation of angiography-derived fractional flow reserve (angio-FFR) using the equation of angio-IMR = estimated hyperemic Pa × angio-FFR × [vessel length/(K × V_diastole)]. The primary outcome was a composite of cardiac death or readmission due to heart failure at 28 months after index procedure. Angio-IMR demonstrated a moderate correlation with HMR (R = 0.74, p < 0.001) and its diagnostic accuracy, sensitivity, specificity, and area under the curve to diagnose INOCA were 79.8, 83.1, 78.0, and 0.84, respectively, with a best cut-off of 25.1. Among prognostic cohort, patients with angio-IMR ≥25.1 showed a significantly higher risk of cardiac death or readmission due to heart failure than those with an angio-IMR <25.1 (18.6 vs. 5.4%, adjusted HR 9.66, 95% CI 2.04–45.65, p = 0.004). Angio-IMR ≥25.1 was an independent predictor for cardiac death or readmission due to heart failure (HR 11.15, 95% CI 1.76–70.42, p = 0.010).

Conclusions: Angio-IMR showed a moderate correlation with HMR and high accuracy to predict microcirculatory dysfunction. Angio-IMR measured after PCI predicts the risk of cardiac death or readmission due to heart failure in patients with CAD.

Clinical Trial Registration: Diagnostic and Prognostic Value of Angiography-derived IMR (CHART-MiCro), NCT04825028.

Melatonin attenuates low shear stress-induced pyroptosis and endothelial cell dysfunction via the RORα/miR-223/STAT-3 signalling pathway

Endothelial cells sense changes in blood flow shear stress and affect the progression of atherosclerotic plaques. Pyroptosis is an inflammatory form of cell death and has been implicated in cardiovascular diseases. Melatonin and its nuclear receptor retinoid-related orphan receptor α (RORα) have protective effects on the development of atherosclerosis. To date, whether melatonin can prevent endothelial cell pyroptosis and dysfunction in pathological shear stress remains unclear. In the present study, human umbilical vein endothelial cells (ECs) were cultured under low shear stress conditions (5 dyne/cm²) for 24 h and treated with or without melatonin (2 µmol/l). The binding sites of the microRNA (miR)-223 promoter and RORα were predicted using the JASPAR website. Expression of pyroptosis-related proteins, including cleaved N-terminal gasdermin D, caspase-1, intercellular adhesion molecule 1 (ICAM-1) and nitric oxide (NO) were assessed. The results indicated that low shear stress increased pyroptosis and ICAM-1 expression, whereas it decreased NO levels. Melatonin alleviated pyroptosis and ICAM-1 expression and increased the production of NO in ECs. Further assessment revealed that low-level shear stress decreased RORα protein and mRNA expression, whereas melatonin would bind to RORα and thereby promoted miR-223 transcription in ECs. The present study also identified signal transducer and activator of transcription 3 (STAT-3) as a potential target gene of miR-223-3p. When transfected with miR-223 inhibitor, ECs up-regulated the expression of pyroptosis-related proteins and ICAM-1, and down-regulated NO levels. By contrast, silencing STAT-3 expression diminished the protective effect of miR-223. These results indicated that melatonin prevented ECs from undergoing pyroptosis and alleviated dysfunction via the RORα/miR-223/STAT-3 signalling pathway. This information could aid in the development of novel therapeutic approaches and provide new insights into atherosclerosis.

Sex Differences in the Non-infarct-Related Artery-Based Quantitative Flow Ratio in Patients With ST-Elevation Myocardial Infarction: A Retrospective Study

Introduction: It has been reported that sex has well-established relationships with the prevalence of coronary artery disease (CAD) and the major adverse cardiovascular events. Compared with men, the difference of coronary artery and myocardial characteristics in women has effects on anatomical and functional evaluations. 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 acute myocardial infarction patients is unknown. This study aimed to evaluate the sex differences in the non-infarct-related artery (NIRA)-based QFR in patients with ST-elevation myocardial infarction (STEMI).

Methods: In this study, 353 patients with STEMI who underwent angiographic cQFR assessment and interventional therapy were included. According to contrast-flow QFR (cQFR) standard operating procedures: reliable software was used to modeling the hyperemic flow velocity derived from coronary angiography in the absence of pharmacologically induced hyperemia. 353 patients were divided into two groups according to sex. A cQFR ≤0.80 was considered hemodynamically significant, whereas invasive coronary angiography (ICA) luminal stenosis ≥50% was considered obstructive. Demographics, clinical data, NIRA-related anatomy, and functional cQFR values were recorded. Clinical outcomes included the NIRA reclassification rate between men and women, according to the ICA and cQFR assessments.

Results: Women were older and had a higher body mass index (BMI) than men. The levels of diastolic blood pressure, troponin I, peak creatine kinase-MB, low-density lipoprotein cholesterol, N terminal pro B-type natriuretic peptide, stent diameter, and current smoking rate were found to be significantly lower in the female group than in the male group. Women had a lower likelihood of a positive cQFR ≤0.80 for the same degree of stenosis and a lower rate of NIRA revascularization. Independent predictors of positive cQFR included male sex and diameter stenosis (DS) >70%.

Conclusions: cQFR values differ between the sexes, as women have a higher cQFR value for the same degree of stenosis. The findings suggest that QFR variations by sex require specific interpretation, as these differences may affect therapeutic decision-making and clinical outcomes.

The importance of three dimensional coronary artery reconstruction accuracy when computing virtual fractional flow reserve from invasive angiography

Three dimensional (3D) coronary anatomy, reconstructed from coronary angiography (CA), is now being used as the basis to compute 'virtual' fractional flow reserve (vFFR), and thereby guide treatment decisions in patients with coronary artery disease (CAD). Reconstruction accuracy is therefore important. Yet the methods required remain poorly validated. Furthermore, the magnitude of vFFR error arising from reconstruction is unkown. We aimed to validate a method for 3D CA reconstruction and determine the effect this had upon the accuracy of vFFR. Clinically realistic coronary phantom models were created comprosing seven standard stenoses in aluminium and 15 patient-based 3D-printed, imaged with CA, three times, according to standard clinical protocols, yielding 66 datasets. Each was reconstructed using epipolar line projection and intersection. All reconstructions were compared against the real phantom models in terms of minimal lumen diameter, centreline and surface similarity. 3D-printed reconstructions (n = 45) and the reference files from which they were printed underwent vFFR computation, and the results were compared. The average error in reconstructing minimum lumen diameter (MLD) was 0.05 (± 0.03 mm) which was < 1% (95% CI 0.13-1.61%) compared with caliper measurement. Overall surface similarity was excellent (Hausdorff distance 0.65 mm). Errors in 3D CA reconstruction accounted for an error in vFFR of ± 0.06 (Bland Altman 95% limits of agreement). Errors arising from the epipolar line projection method used to reconstruct 3D coronary anatomy from CA are small but contribute to clinically relevant errors when used to compute vFFR.

A prospective multicenter validation study for a novel angiography-derived physiological assessment software: Rationale and design of the radiographic imaging validation and evaluation for Angio-iFR (ReVEAL iFR) study

Angiography-derived physiological assessment of coronary lesions has emerged as an alternative to wire-based assessment aiming at less-invasiveness and shorter procedural time as well as cost effectiveness in physiology-guided decision making. However, current available image-derived physiology software have limitations including the requirement of multiple projections and are time consuming. METHODS/DESIGN: The ReVEAL iFR (Radiographic imaging Validation and EvALuation for Angio-iFR) trial is a multicenter, multicontinental, validation study which aims to validate the diagnostic accuracy of the Angio-iFR medical software device (Philips, San Diego, US) in patients undergoing angiography for Chronic Coronary Syndrome (CCS). The Angio-iFR will enable operators to predict both the iFR and FFR value within a few seconds from a single projection of cine angiography by using a lumped parameter fluid dynamics model. Approximately 440 patients with at least one de-novo 40% to 90% stenosis by visual angiographic assessment will be enrolled in the study. The primary endpoint is the sensitivity and specificity of the iFR and FFR for a given lesion compared to the corresponding invasive measures. The enrollment started in August 2019, and was completed in March 2021. SUMMARY: The Angio-iFR system has the potential of simplifying physiological evaluation of coronary stenosis compared with available systems, providing estimates of both FFR and iFR. The ReVEAL iFR study will investigate the predictive performance of the novel Angio-iFR software in CCS patients. Ultimately, based on its unique characteristics, the Angio-iFR system may contribute to improve adoption of functional coronary assessment and the workflow in the catheter laboratory.

The relationship between coronary stenosis morphology and fractional flow reserve: a computational fluid dynamics modelling study

Aims

International guidelines mandate the use of fractional flow reserve (FFR) and/or non-hyperaemic pressure ratios to assess the physiological significance of moderate coronary artery lesions to guide revascularization decisions. However, they remain underused such that visual estimation of lesion severity continues to be the predominant decision-making tool. It would be pragmatic to have an improved understanding of the relationship between lesion morphology and haemodynamics. The aim of this study was to compute virtual FFR (vFFR) in idealized coronary artery geometries with a variety of stenosis and vessel characteristics.

Methods and results

Coronary artery geometries were modelled, based upon physiologically realistic branched arteries. Common stenosis characteristics were studied, including % narrowing, length, eccentricity, shape, number, position relative to branch, and distal (myocardial) resistance. Computational fluid dynamics modelling was used to calculate vFFRs using the VIRTUheart™ system. Percentage lesion severity had the greatest effect upon FFR. Any ≥80% diameter stenosis in two views (i.e. concentric) was physiologically significant (FFR ≤ 0.80), irrespective of length, shape, or vessel diameter. Almost all eccentric stenoses and all 50% concentric stenoses were physiologically non-significant, whilst 70% uniform concentric stenoses about 10 mm long straddled the ischaemic threshold (FFR 0.80). A low microvascular resistance (MVR) reduced FFR on average by 0.05, and a high MVR increased it by 0.03.

Conclusion

Using computational modelling, we have produced an analysis of vFFR that relates stenosis characteristics to haemodynamic significance. The strongest predictor of a positive vFFR was a concentric, ≥80% diameter stenosis. The importance of MVR was quantified. Other lesion characteristics have a limited impact.

Invasive Coronary Physiology After Stent Implantation: Another Step Toward Precision Medicine

Intracoronary physiology is routinely used in setting the indication for percutaneous coronary intervention (PCI) but seldom in assessing procedural results. This attitude is increasingly challenged by accumulated evidence demonstrating the value of post-PCI functional assessment in predicting long-term patient outcomes. Besides fractional flow reserve, a number of new indexes recently incorporated to clinical practice, including nonhyperemic pressure and functional angiographic indexes, provide new opportunities for the physiological assessment of PCI results. Largely, the benefit of these tools is derived from longitudinal analysis of the treated vessel, which allows precise identification of the vessel segment accounting for a suboptimal functional result and enabling operators to perform accurate PCI optimization. In this document the authors review available evidence supporting why physiological assessment should be extended to immediate post-PCI with the aim of improving patient outcomes. A step-by-step guide on how available physiological tools can be used for such purpose is provided.

Immediate post-procedural functional assessment of percutaneous coronary intervention: current evidence and future directions

Percutaneous coronary intervention (PCI) guided by coronary physiology provides symptomatic benefit and improves patient outcomes. Nevertheless, over one-fourth of patients still experience recurrent angina or major adverse cardiac events following the index procedure. Coronary angiography, the current workhorse for evaluating PCI efficacy, has limited ability to identify suboptimal PCI results. Accumulating evidence supports the usefulness of immediate post-procedural functional assessment. This review discusses the incidence and possible mechanisms behind a suboptimal physiology immediately after PCI. Furthermore, we summarize the current evidence base supporting the usefulness of immediate post-PCI functional assessment for evaluating PCI effectiveness, guiding PCI optimization, and predicting clinical outcomes. Multiple observational studies and post hoc analyses of datasets from randomized trials demonstrated that higher post-PCI functional results are associated with better clinical outcomes as well as a reduced rate of residual angina and repeat revascularization. As such, post-PCI functional assessment is anticipated to impact patient management, secondary prevention, and resource utilization. Pre-PCI physiological guidance has been shown to improve clinical outcomes and reduce health care costs. Whether similar benefits can be achieved using post-PCI physiological assessment requires evaluation in randomized clinical outcome trials.

Vessel fractional flow reserve in assessment of non-culprit lesions in ST elevation myocardial infarction

Objectives

We sought to evaluate the physiology of non-culprit lesions by using vessel fractional flow reserve (vFFR) among patients with ST elevation myocardial infarction (STEMI) and multivessel disease (MVD).

Methods

From January 2017 to December 2019, 354 patients with STEMI in the Taipei Veterans General Hospital Acute Myocardial Infarction Registry were screened. Patients who underwent successful primary percutaneous coronary intervention (PCI) for culprit lesions, with at least one non-culprit lesion with stenosis of ≥50%, were eligible. vFFR was computed retrospectively.

Results

A total of 156 patients with 217 non-culprit lesions were eligible for this study. Aortic root pressure and two good angiograms were available for 139 non-culprit lesions for vFFR analysis. Based on the vFFR analysis, 59 non-culprit lesions (43.2%) had a vFFR value >0.80, and PCI was deferred in 45 lesions (76.3%). Meanwhile, 80 non-culprit lesions (56.8%) had a vFFR value ≤0.80; however, PCI was only performed in 31 lesions (38.7%) (p=0.142). The incidence of vessel-oriented composite endpoint was numerically higher in non-culprit lesions with vFFR ≤0.80 than those with vFFR >0.80 (6.3% vs 1.7%, HR: 3.59, 95% CI: 0.42 to 30.8, p=0.243).

Conclusion

Functional incomplete revascularisation is common among patients with STEMI and MVD. The adoption of vFFR to assess non-culprit lesions may reclassify the coronary revascularisation strategy that is usually guided by angiography only in this acute setting.