Functional classification discordance in intermediate coronary stenoses between fractional flow reserve and angiography-based quantitative flow ratio

Coronary Artery Stenosis Evaluation by Angiography-Derived FFR: Validation by Positron Emission Tomography and Invasive Thermodilution

BACKGROUND

Fractional flow reserve (FFR) derived from invasive coronary angiography (QFR) is promising for evaluation of intermediate coronary artery stenosis.

OBJECTIVES

The authors aimed to compare the diagnostic performance of QFR and the guideline-recommended invasive FFR using 82Rubidium positron emission tomography (82Rb-PET) myocardial perfusion imaging as reference standard.

METHODS

This is a prospective, observational study of symptomatic patients with suspected obstructive coronary artery disease on coronary computed tomography angiography (≥50% diameter stenosis in ≥1 vessel). All patients were referred to 82Rb-PET and invasive coronary angiography with FFR and QFR assessment of all intermediate (30%-90% diameter stenosis) stenoses. Main analyses included a comparison of the ability of QFR and FFR to identify reduced myocardial blood flow (<2 mL/g/min) during vasodilation and/or relative perfusion abnormalities (summed stress score ≥4 in ≥2 adjacent segments).

RESULTS

A total of 250 patients (320 vessels) with indication for invasive physiological assessment were included. The continuous relationship of 82Rb-PET stress myocardial blood flow per 0.10 increase in FFR was +0.14 mL/g/min (95% CI: 0.07-0.21 mL/g/min) and +0.08 mL/g/min (95% CI: 0.02-0.14 mL/g/min) per 0.10 QFR increase. Using 82Rb-PET as reference, QFR and FFR had similar diagnostic performance on both a per-patient level (accuracy: 73%; 95% CI: 67%-79%; vs accuracy: 71%; 95% CI: 64%-78%) and per-vessel level (accuracy: 70%; 95% CI: 64%-75%; vs accuracy: 68%; 95% CI: 62%-73%). The per-vessel feasibility was 84% (95% CI: 80%-88%) for QFR and 88% (95% CI: 85%-92%) for FFR by intention-to-diagnose analysis.

CONCLUSIONS

With 82Rb-PET as reference modality, the wire-free QFR solution showed similar diagnostic accuracy as invasive FFR in evaluation of intermediate coronary stenosis. (DAN-NICAD - Danish Study of Non-Invasive Diagnostic Testing in Coronary Artery Disease; NCT02264717).

Coronary functional assessment in non-obstructive coronary artery disease: Present situation and future direction

Non-obstructive coronary artery disease (CAD), which is defined as coronary stenosis <50%, has been increasingly recognized as an emerging entity in clinical practice. Vasomotion abnormality and coronary microvascular dysfunction are two major mechanisms contributing to the occur of angina with non-obstructive CAD. Although routine coronary functional assessment is limited due to several disadvantages, functional evaluation can help to understand the pathophysiological mechanism and/or to exclude specific etiologies. In this review, we summarized the potential mechanisms involved in ischemia with non-obstructive coronary arteries (INOCA) and myocardial infarction with non-obstructive coronary arteries (MINOCA), the two major form of non-obstructive CAD. Additionally, we reviewed currently available functional assessment indices and their use in non-obstructive CAD. Furthermore, we speculated that novel technique combined anatomic and physiologic parameters might provide more individualized therapeutic choice for patients with non-obstructive CAD.

Characterization of quantitative flow ratio and fractional flow reserve discordance using doppler flow and clinical follow-up

The physiological mechanisms of quantitative flow ratio and fractional flow reserve disagreement are not fully understood. We aimed to characterize the coronary flow and resistance profile of intermediate stenosed epicardial coronary arteries with concordant and discordant FFR and QFR. Post-hoc analysis of the DEFINE-FLOW study. Anatomical and Doppler-derived physiological parameters were compared for lesions with FFR+QFR- (n = 18) vs. FFR+QFR+ (n = 43) and for FFR-QFR+ (n = 34) vs. FFR-QFR- (n = 139). The association of QFR results with the two-year rate of target vessel failure was assessed in the proportion of vessels (n = 195) that did not undergo revascularization. Coronary flow reserve was higher [2.3 (IQR: 2.1-2.7) vs. 1.9 (IQR: 1.5-2.4)], hyperemic microvascular resistance lower [1.72 (IQR: 1.48-2.31) vs. 2.26 (IQR: 1.79-2.87)] and anatomical lesion severity less severe [% diameter stenosis 45.5 (IQR: 41.5-52.5) vs. 58.5 (IQR: 53.1-64.0)] for FFR+QFR- lesions compared with FFR+QFR+ lesions. In comparison of FFR-QFR+ vs. FFR-QFR- lesions, lesion severity was more severe [% diameter stenosis 55.2 (IQR: 51.7-61.3) vs. 43.4 (IQR: 35.0-50.6)] while coronary flow reserve [2.2 (IQR: 1.9-2.9) vs. 2.2 (IQR: 1.9-2.6)] and hyperemic microvascular resistance [2.34 (IQR: 1.85-2.81) vs. 2.57 (IQR: 2.01-3.22)] did not differ. The agreement and diagnostic performance of FFR using hyperemic stenosis resistance (> 0.80) as reference standard was higher compared with QFR and coronary flow reserve. Disagreement between FFR and QFR is partly explained by physiological and anatomical factors. Clinical Trials Registration https://www.clinicaltrials.gov ; Unique identifier: NCT01813435.

Determinants of visual-functional mismatches as assessed by coronary angiography and quantitative flow ratio

OBJECTIVE

We aimed to evaluate the determinants of visual-functional mismatches between quantitative coronary angiography (QCA) and the quantitative flow ratio (QFR).

BACKGROUND

The fractional flow reserve (FFR) has been established as a method to estimate the functional stenosis severity of coronary artery disease and to optimize decision-making for revascularization. The QFR is a novel angiography-derived computational index that can estimate the FFR without pharmacologically induced hyperemia or the use of pressure wire.

METHODS

A total of 504 de novo intermediate-to-severe stable lesions that underwent angiographic and physiological assessments were analyzed. All lesions were divided into four groups based on the significance of visual (QCA-diameter stenosis [DS] > 50% and ≤ 50%) and functional (QFR ≤ 0.80 and > 0.80) stenosis severity. Patient characteristics, angiographic findings, and physiological indices were compared.

RESULTS

One-hundred seventy-eight lesions (35.3%) showed discordant visual-functional assessments; mismatch (QCA-DS > 50% and QFR > 0.80) in 75 lesions (14.9%) and reverse mismatch (QCA-DS ≤ 50% and QFR ≤ 0.80) in 103 lesions (20.4%), respectively. Reverse mismatch was associated with non-diabetes, lower ejection fraction, higher Duke jeopardy score, and lower coronary flow reserve (CFR). Mismatch was associated with smaller QCA-DS, larger reference diameter, shorter lesion length, lower Duke jeopardy score, and higher CFR. Lesion location and microcirculatory resistance was not associated with the prevalence of mismatches. Reverse mismatch group had the higher prevalence of discordant decision-makings between QFR and FFR than the other three groups.

CONCLUSIONS

The CFR and subtended myocardial mass were predictors of visual-functional mismatches between QCA-DS and the QFR. Caution should be exercised in lesions showing QCA-DS/QFR reverse mismatch.

Non-invasive imaging software to assess the functional significance of coronary stenoses: a systematic review and economic evaluation

BACKGROUND

QAngio^® XA 3D/QFR^® (three-dimensional/quantitative flow ratio) imaging software (Medis Medical Imaging Systems BV, Leiden, the Netherlands) and CAAS^® vFFR^® (vessel fractional flow reserve) imaging software (Pie Medical Imaging BV, Maastricht, the Netherlands) are non-invasive technologies to assess the functional significance of coronary stenoses, which can be alternatives to invasive fractional flow reserve assessment.

OBJECTIVES

The objectives were to determine the clinical effectiveness and cost-effectiveness of QAngio XA 3D/QFR and CAAS vFFR.

METHODS

We performed a systematic review of all evidence on QAngio XA 3D/QFR and CAAS vFFR, including diagnostic accuracy, clinical effectiveness, implementation and economic analyses. We searched MEDLINE and other databases to January 2020 for studies where either technology was used and compared with fractional flow reserve in patients with intermediate stenosis. The risk of bias was assessed with quality assessment of diagnostic accuracy studies. Meta-analyses of diagnostic accuracy were performed. Clinical and implementation outcomes were synthesised narratively. A simulation study investigated the clinical impact of using QAngio XA 3D/QFR. We developed a de novo decision-analytic model to estimate the cost-effectiveness of QAngio XA 3D/QFR and CAAS vFFR relative to invasive fractional flow reserve or invasive coronary angiography alone. Scenario analyses were undertaken to explore the robustness of the results to variation in the sources of data used to populate the model and alternative assumptions.

RESULTS

Thirty-nine studies (5440 patients) of QAngio XA 3D/QFR and three studies (500 patients) of CAAS vFFR were included. QAngio XA 3D/QFR had good diagnostic accuracy to predict functionally significant fractional flow reserve (≤ 0.80 cut-off point); contrast-flow quantitative flow ratio had a sensitivity of 85% (95% confidence interval 78% to 90%) and a specificity of 91% (95% confidence interval 85% to 95%). A total of 95% of quantitative flow ratio measurements were within 0.14 of the fractional flow reserve. Data on the diagnostic accuracy of CAAS vFFR were limited and a full meta-analysis was not feasible. There were very few data on clinical and implementation outcomes. The simulation found that quantitative flow ratio slightly increased the revascularisation rate when compared with fractional flow reserve, from 40.2% to 42.0%. Quantitative flow ratio and fractional flow reserve resulted in similar numbers of subsequent coronary events. The base-case cost-effectiveness results showed that the test strategy with the highest net benefit was invasive coronary angiography with confirmatory fractional flow reserve. The next best strategies were QAngio XA 3D/QFR and CAAS vFFR (without fractional flow reserve). However, the difference in net benefit between this best strategy and the next best was small, ranging from 0.007 to 0.012 quality-adjusted life-years (or equivalently £140-240) per patient diagnosed at a cost-effectiveness threshold of £20,000 per quality-adjusted life-year.

LIMITATIONS

Diagnostic accuracy evidence on CAAS vFFR, and evidence on the clinical impact of QAngio XA 3D/QFR, were limited.

CONCLUSIONS

Quantitative flow ratio as measured by QAngio XA 3D/QFR has good agreement and diagnostic accuracy compared with fractional flow reserve and is preferable to standard invasive coronary angiography alone. It appears to have very similar cost-effectiveness to fractional flow reserve and, therefore, pending further evidence on general clinical benefits and specific subgroups, could be a reasonable alternative. The clinical effectiveness and cost-effectiveness of CAAS vFFR are uncertain. Randomised controlled trial evidence evaluating the effect of quantitative flow ratio on clinical and patient-centred outcomes is needed.

FUTURE WORK

Studies are required to assess the diagnostic accuracy and clinical feasibility of CAAS vFFR. Large ongoing randomised trials will hopefully inform the clinical value of QAngio XA 3D/QFR.

STUDY REGISTRATION

This study is registered as PROSPERO CRD42019154575.

FUNDING

This project was funded by the National Institute for Health Research (NIHR) Evidence Synthesis programme and will be published in full in Health Technology Assessment; Vol. 25, No. 56. See the NIHR Journals Library website for further project information.

Coronary microcirculation assessment using functional angiography: Development of a wire-free method applicable to conventional coronary angiograms

OBJECTIVES

We aimed to develop a novel wire- and adenosine-free microcirculatory resistive index from functional angiography (angio-IMR) to estimate coronary microcirculatory resistance, and to investigate how this method can improve clinical interpretation of physiological stenosis assessment with quantitative flow ratio (QFR).

BACKGROUND

Hyperemic index of coronary microcirculatory resistance (IMR) is a widely used tool to assess microcirculatory dysfunction. However, the need of dedicated intracoronary wire and hyperemia limits its adoption in clinical practice.

METHODS

We performed our study in two separate stages: (1) development of a formula (angio-IMR) to estimate IMR from resting angiograms and aortic pressure (Pa), and (2) validation of the method in a clinical population using invasively measured IMR as reference. Additionally, QFR diagnostic performance was assessed considering angio-IMR values.

RESULTS

We developed the formula: angio-IMR = (Pa-[0.1*Pa])*QFR*e-Tmn (where e-Tmn is an estimation of hyperaemic mean transit time) and validated it in 115 vessels (104 patients). Angio-IMR correlated well with IMR (Spearman's rho = 0.70, p < 0.001). Sensitivity, specificity, positive and negative predictive value, accuracy and area under the curve of angio-IMR to predict IMR were 87.5% (73.2-95.8), 85.3% (75.3-92.4), 76.1% (64.5-84.8), 92.8% (84.9-96.7), 85% and 0.90 (0.83-0.95), respectively. False positive QFR measurements decreased from 19.5% to 8.5% when angio-IMR was incorporated into the QFR interpretation workflow.

CONCLUSIONS

Estimation of IMR without physiology wire and adenosine is feasible. Coronary microcirculatory dysfunction causing high IMR can be ruled-out with high confidence in vessels with low angio-IMR. Awareness of angio-IMR contributes to a better clinical interpretation of functional stenosis assessment with QFR.

Quantitative flow ratio as a new tool for angiography-based physiological evaluation of coronary artery disease: a review

The functional evaluation of coronary stenoses has obtained important clinical results in recent years, resulting in strong guideline recommendations. Nonetheless, the use of coronary wire-based functional evaluation has not yet become part of the routine in catheterization laboratories for several reasons, including the need to advance a wire into the coronary vessel to interrogate the stenosis. Angiography-derived indexes have been introduced to expand the current use of physiology to estimate the functional meaning of a stenosis on the basis of angiographic data only. The most studied and validated angiography-derived index is certainly the quantitative flow ratio. This article will summarize the basics of the quantitative flow ratio, the related validation studies and its current and future applications.