Murray law-based quantitative flow ratio to assess left main bifurcation stenosis: selecting the angiographic projection matters

Murray law-based quantitative flow ratio (µQFR) assesses fractional flow reserve (FFR) in bifurcation lesions using a single angiographic view, enhancing the feasibility of analysis; however, accuracy may be compromised in suboptimal angiographic projections. FFRCT is a well-validated non-invasive method measuring FFR from coronary computed tomographic angiography (CCTA). We evaluated the feasibility of µQFR in left main (LM) bifurcations, the impact of the optimal/suboptimal fluoroscopic view with respect to CCTA, and its diagnostic concordance with FFRCT. In 300 patients with three-vessel disease, the values of FFRCT and µQFR were compared at distal LM, proximal left anterior descending artery (pLAD) and circumflex artery (pLCX). The optimal viewing angle of LM bifurcation was defined on CCTA by 3-dimensional coordinates and converted into a 2-dimensional fluoroscopic view. The best fluoroscopic projection was considered the closest angulation to the optimal viewing angle on CCTA. µQFR was successfully computed in 805 projections. In the best projections, µQFR sensitivity was 88.2% (95% CI 76.1-95.6) and 84.8% (71.1-93.7), and specificity was 96.8% (93.8-98.6) and 97.2% (94.4-98.9), in pLAD and pLCX, respectively, with regard to FFRCT. The AUC of µQFR for predicting FFRCT ≤ 0.80 tended to be improved using the best versus suboptimal projections (0.94 vs. 0.89 [p = 0.048] in pLAD; 0.94 vs. 0.88 [p = 0.075] in pLCX). Computation of µQFR in LM bifurcations using a single angiographic view showed high feasibility from post-hoc analysis of coronary angiograms obtained for clinical purposes. The fluoroscopic viewing angle influences the diagnostic performance of physiological assessment using a single angiographic view.

The ability of computed tomography angiography to predict 5-year mortality in the SYNTAX III REVOLUTION trial

BACKGROUND

The feasibility of using coronary computed tomography angiography (CCTA) for long-term prediction of vital prognosis post-revascularization remains unknown.

OBJECTIVES

To compare the prognostic value of the SYNTAX score II 2020 (SS-2020) derived from invasive coronary angiography (ICA) or CCTA in patients with three-vessel disease and/or left main coronary artery disease undergoing percutaneous or surgical revascularization.

METHODS

In the SYNTAX III REVOLUTION trial, the probability of death at five years was retrospectively assessed by calculating the SS-2020 using ICA and CCTA. High- and low-risk patients for mortality were categorized according to the median percentages of predicted mortality based on both modalities. The discriminative abilities of the SS-2020 were assessed using Harrell's C statistic.

RESULTS

The vital status at five years of the 215 patients revascularized percutaneously (64 patients, 29.8%) or surgically (151 patients, 70.2%) was established through national registries. In patients undergoing revascularization, the SS-2020 was possibly helpful in discriminating vital prognosis at 5 years, with similar results seen with ICA and CCTA (C-index with ICA ​= ​0.75, intercept ​= ​-0.19, slope ​= ​0.92 and C-index with CCTA ​= ​0.75, intercept ​= ​-0.22, slope ​= ​0.99). In high- and low-risk patients, Kaplan-Meier estimates showed significant, and almost identical relative differences in observed mortality, irrespective of imaging modality (ICA: 93.8% vs 78.7%, log-lank P ​< ​0.001; CCTA: 93.7% vs 78.5%, log-lank P ​< ​0.001).

CONCLUSIONS

The predictive ability of the SS-2020 for five-year all-cause mortality derived from ICA and CCTA was comparable, and could helpfully discriminate vital prognosis in high- and low-risk patients.

Intravascular Imaging versus Physiological Assessment versus Biomechanics-Which Is a Better Guide for Coronary Revascularization

Today, coronary artery disease (CAD) continues to be a prominent cause of death worldwide. A reliable assessment of coronary stenosis represents a prerequisite for the appropriate management of CAD. Nevertheless, there are still major challenges pertaining to some limitations of current imaging and functional diagnostic modalities. The present review summarizes the current data on invasive functional and intracoronary imaging assessment using optical coherence tomography (OCT), and intravascular ultrasound (IVUS). Amongst the functional parameters-on top of fractional flow reserve (FFR) and instantaneous wave-free ratio (iFR)-we point to novel angiography-based measures such as quantitative flow ratio (QFR), vessel fractional flow reserve (vFFR), angiography-derived fractional flow reserve (FFRangio), and computed tomography-derived flow fractional reserve (FFR-CT), as well as hybrid approaches focusing on optical flow ratio (OFR), computational fluid dynamics and attempts to quantify the forces exaggerated by blood on the coronary plaque and vessel wall.

Application of physics-based flow models in cardiovascular medicine: Current practices and challenges

Personalized physics-based flow models are becoming increasingly important in cardiovascular medicine. They are a powerful complement to traditional methods of clinical decision-making and offer a wealth of physiological information beyond conventional anatomic viewing using medical imaging data. These models have been used to identify key hemodynamic biomarkers, such as pressure gradient and wall shear stress, which are associated with determining the functional severity of cardiovascular diseases. Importantly, simulation-driven diagnostics can help researchers understand the complex interplay between geometric and fluid dynamic parameters, which can ultimately improve patient outcomes and treatment planning. The possibility to compute and predict diagnostic variables and hemodynamics biomarkers can therefore play a pivotal role in reducing adverse treatment outcomes and accelerate development of novel strategies for cardiovascular disease management.

Site vs. core laboratory variability in computed tomographic angiography-derived SYNTAX scores in the SYNTAX III trial

AIMS 

To investigate the variability between site and core laboratory (CL) calculation of the anatomical SYNTAX score (SS) based on coronary computed tomography angiography (CTA) alone and functional SS based on coronary CTA and fractional flow reserve derived from computed tomography (FFRCT) in the SYNTAX III trial.

METHODS AND RESULTS 

The SYNTAX III trial was a multicentre, international study that included 223 patients with three-vessel disease with or without left main involvement. Functional SS was computed by subtracting non-flow limiting stenoses (FFRCT > 0.80) from anatomical SS. SS was combined with clinical information to generate the SYNTAX score II (SS II) that provides treatment recommendations. The mean anatomical SS based on coronary CTA alone was 33.4 ± 12.7 by sites and 37.1 ± 13.4 by CL (P < 0.001). The mean functional SS based on coronary CTA and FFRCT was 30.5 ± 13.0 by sites and 33.3 ± 13.6 by CL (P < 0.001). The intraclass correlation coefficient was 0.49 [95% confidence interval (CI) 0.37-0.59) in anatomical SS and 0.62 (95% CI 0.52-0.70) in functional SS. The Cohen's κ comparing treatment recommendation between sites and CL was 0.68 (95% CI 0.58-0.78) based on anatomical SS and 0.71 (95% CI 0.60-0.82) based on functional SS.

CONCLUSION 

The mean anatomical SS derived from coronary CTA alone and functional SS based on coronary CTA and FFRCT were higher when assessed by the CL than by the sites themselves. However, substantial agreement in treatment recommendation by SS II between sites and CL was demonstrated.

CLINICAL TRIALS.GOV IDENTIFIER

NCT02385279.

FFRCT and CT perfusion: A review on the evaluation of functional impact of coronary artery stenosis by cardiac CT

Coronary computed tomography angiography (CCTA) is at the frontline of the diagnostic strategies to detect coronary artery disease (CAD). Anatomical information have proven to be insufficient to detect hemodynamic significant epicardial stenosis. In the present invited review we discuss on FFR_CT and stress CTP, emerging technologies for an accurate and comprehensive evaluation of patients with suspected CAD, offering both anatomical (i.e. luminal and plaque) and functional assessment in one single technique.

Feasibility of planning coronary artery bypass grafting based only on coronary computed tomography angiography and CT-derived fractional flow reserve: a pilot survey of the surgeons involved in the randomized SYNTAX III Revolution trial

OBJECTIVES

Invasive coronary angiography has been the preferred diagnostic method to guide the decision-making process between coronary artery bypass grafting (CABG) and percutaneous coronary intervention and plan a surgical revascularization procedure. Guidelines recommend a heart team approach and assessment of coronary artery disease (CAD) complexity, objectively quantified by the anatomical SYNTAX score. Coronary computed tomography angiography (CCTA) and CT-derived fractional flow reserve (FFRCT) are emerging technologies in the diagnosis of stable CAD. In this study, data from patients with left main or 3-vessel CAD who underwent CABG were evaluated to assess the feasibility of developing a surgical plan based on CCTA integrated with FFRCT. The primary objective was to assess the theoretical feasibility of surgical decision-making and treatment planning based only on non-invasive imaging.

METHODS

This study represents a survey of surgeons involved in the SYNTAX III Revolution trial. In this trial, heart teams were randomized to make treatment decisions using CTA. CCTAs and FFRCT results of 20 patients were presented to 5 cardiac surgeons.

RESULTS

Surgical treatment decision-making based on CCTA with FFRCT was considered feasible by a panel of surgeons in 84% of the cases with an excellent agreement on the number of anastomoses to be made in each patient (intraclass correlation coefficient 0.77, 95% confidence interval 0.35-0.96).

CONCLUSIONS

Using non-invasive imaging only in patients with left main or 3-vessel CAD, an excellent agreement on treatment planning and the number of anastomoses was found among cardiac surgeons. Thus, CABG planning based on non-invasive imaging appears feasible. Further investigation is warranted to determine the safety and feasibility in clinical practice.

A new CFD based non-invasive method for functional diagnosis of coronary stenosis

Background

Accurate functional diagnosis of coronary stenosis is vital for decision making in coronary revascularization. With recent advances in computational fluid dynamics (CFD), fractional flow reserve (FFR) can be derived non-invasively from coronary computed tomography angiography images (FFR_CT) for functional measurement of stenosis. However, the accuracy of FFR_CT is limited due to the approximate modeling approach of maximal hyperemia conditions. To overcome this problem, a new CFD based non-invasive method is proposed.

Methods

Instead of modeling maximal hyperemia condition, a series of boundary conditions are specified and those simulated results are combined to provide a pressure-flow curve for a stenosis. Then, functional diagnosis of stenosis is assessed based on parameters derived from the obtained pressure-flow curve.

Results

The proposed method is applied to both idealized and patient-specific models, and validated with invasive FFR in six patients. Results show that additional hemodynamic information about the flow resistances of a stenosis is provided, which cannot be directly obtained from anatomy information. Parameters derived from the simulated pressure-flow curve show a linear and significant correlations with invasive FFR (r > 0.95, P < 0.05).

Conclusion

The proposed method can assess flow resistances by the pressure-flow curve derived parameters without modeling of maximal hyperemia condition, which is a new promising approach for non-invasive functional assessment of coronary stenosis.

Functional Evaluation of Coronary Disease by CT Angiography

In recent years, several technical developments in the field of cardiac computed tomography (CT) have made possible the extraction of functional information from an anatomy-based examination. Several different lines have been explored and will be reviewed in the present paper, namely: 1) myocardial perfusion imaging; 2) transluminal attenuation gradients and corrected coronary opacification indexes; 3) fractional flow reserve computed from CT; and 4) extrapolation from atherosclerotic plaque characteristics. In view of these developments, cardiac CT has the potential to become in the near future a truly 2-in-1 noninvasive evaluation for coronary artery disease.

Bypass Grafting Versus Percutaneous Intervention-Which Is Better in Multivessel Coronary Disease: Lessons From SYNTAX and Beyond

The landmark Synergy between Percutaneous Coronary Intervention with Taxus and Cardiac Surgery (SYNTAX) Trial has aided in reducing the area of uncertainty in decision-making between percutaneous coronary intervention (PCI) and coronary artery bypass graft (CABG) surgery in patients with complex coronary artery disease. As part of the SYNTAX Trial, quantification of the coronary artery disease burden was prospectively undertaken by the Heart Team - consisting of at least an interventional cardiologist and cardiac surgeon - utilising the anatomical SYNTAX Score (www.syntaxscore.com) as a clinical tool in order to agree that equivalent anatomical revascularisation could be achieved. The anatomical SYNTAX Score is now advocated in both European and US revascularisation guidelines to guide decision-making between CABG and PCI as part of the SYNTAX pioneered Heart Team approach. In addition, the SYNTAX Trial has lead to the development and validation of the SYNTAX Score II, in which the anatomical SYNTAX Score was augmented with clinical variables, to allow for more objective and tailored decision making for the individual patient. Prospective validation of the SYNTAX Score II tool is currently ongoing in the SYNTAX II (ClinicalTrials.gov Identifier: NCT02015832) and EXCEL (ClinicalTrials.gov identifier: NCT01205776) trials. The present paper presents lessons learned from SYNTAX, including the development and/or validation of several SYNTAX based clinical tools, and the potential implications for current and future clinical practice.

Fractional Flow Reserve Derived from Coronary Imaging and Computational Fluid Dynamics

The assessment of functional severity of atherosclerotic stenoses in patients with coronary artery disease by invasive fractional flow reserve (FFR) measurement requires coronary artery cannulation, advancement of a wire and intravenous adenosine infusion with inherent procedure-related risk and costs. Coronary computed tomographic angiography (CCTA) and rotational coronary angiography (RA) have been recently used in conjunction with computational fluid dynamics (CFD) and image-based modelling for the determination of FFR without the need for additional imaging, modification of acquisition protocols or administration of medication. FFR derived from CCTA was demonstrated as superior to measures of CCTA stenosis severity for determination of lesion-specific ischaemia. Estimation of FFR from RA images and CFD provides a less invasive alternative to conventional FFR measurement while estimated values are in agreement with measured values. These new, combined anatomic-functional assessments have the potential to simplify the noninvasive diagnosis of coronary artery disease with a single study to identify patients with ischaemia-causing stenosis who may benefit from revascularisation.

Widening clinical applications of the SYNTAX Score

The SYNTAX Score (http://www.syntaxscore.com) has established itself as an anatomical based tool for objectively determining the complexity of coronary artery disease and guiding decision-making between coronary artery bypass graft (CABG) surgery and percutaneous coronary intervention (PCI). Since the landmark SYNTAX (Synergy between PCI with Taxus and Cardiac Surgery) Trial comparing CABG with PCI in patients with complex coronary artery disease (unprotected left main or de novo three vessel disease), numerous validation studies have confirmed the clinical validity of the SYNTAX Score for identifying higher-risk subjects and aiding decision-making between CABG and PCI in a broad range of patient types. The SYNTAX Score is now advocated in both the European and US revascularisation guidelines for decision-making between CABG and PCI as part of a SYNTAX-pioneered heart team approach. Since establishment of the SYNTAX Score, widening clinical applications of this clinical tool have emerged. The purpose of this review is to systematically examine the widening applications of tools based on the SYNTAX Score: (1) by improving the diagnostic accuracy of the SYNTAX Score by adding a functional assessment of lesions; (2) through amalgamation of the anatomical SYNTAX Score with clinical variables to enhance decision-making between CABG and PCI, culminating in the development and validation of the SYNTAX Score II, in which objective and tailored decisions can be made for the individual patient; (3) through assessment of completeness of revascularisation using the residual and post-CABG SYNTAX Scores for PCI and CABG patients, respectively. Finally, the future direction of the SYNTAX Score is covered through discussion of the ongoing development of a non-invasive, functional SYNTAX Score and review of current and planned clinical trials.