Functional Assessment Of Coronary Stenosis Research Articles

Determinants of Rejection Rate for Coronary CT Angiography Fractional Flow Reserve Analysis.

Background Coronary artery fractional flow reserve (FFR) derived from CT angiography (FFTCT) enables functional assessment of coronary stenosis. Prior clinical trials showed 13%-33% of coronary CT angiography studies had insufficient quality for quantitative analysis with FFRCT. Purpose To determine the rejection rate of FFRCT analysis and to determine factors associated with technically unsuccessful calculation of FFRCT. Materials and Methods Prospectively acquired coronary CT angiography scans submitted as part of the Assessing Diagnostic Value of Noninvasive FFRCT in Coronary Care (ADVANCE) registry (https://ClinicalTrials.gov: NCT02499679) and coronary CT angiography series submitted for clinical analysis were included. The primary outcome was the FFRCT rejection rate (defined as an inability to perform quantitative analysis with FFRCT). Factors that were associated with FFRCT rejection rate were assessed with multiple linear regression. Results In the ADVANCE registry, FFRCT rejection rate due to inadequate image quality was 2.9% (80 of 2778 patients; 95% confidence interval [CI]: 2.1%, 3.2%). In the 10 621 consecutive patients who underwent clinical analysis, the FFRCT rejection rate was 8.4% (n = 892; 95% CI: 6.2%, 7.2%; P < .001 vs the ADVANCE cohort). The main reason for the inability to perform FFRCT analysis was the presence of motion artifacts (63 of 80 [78%] and 729 of 892 [64%] in the ADVANCE and clinical cohorts, respectively). At multivariable analysis, section thickness in the ADVANCE (odds ratio [OR], 1.04; 95% CI: 1.001, 1.09; P = .045) and clinical (OR, 1.03; 95% CI: 1.02, 1.04; P < .001) cohorts and heart rate in the ADVANCE (OR, 1.05; 95% CI: 1.02, 1.08; P < .001) and clinical (OR, 1.06; 95% CI: 1.05, 1.07; P < .001) cohorts were independent predictors of rejection. Conclusion The rates for technically unsuccessful CT-derived fractional flow reserve in the ADVANCE registry and in a large clinical cohort were 2.9% and 8.4%, respectively. Thinner CT section thickness and lower patient heart rate may increase rates of completion of CT fractional flow reserve analysis. Published under a CC BY 4.0 license. Online supplemental material is available for this article. See also the editorial by Sakuma in this issue.

Adenosine-Free Indexes vs. Fractional Flow Reserve for Functional Assessment of Coronary Stenoses: Systematic Review and Meta-Analysis

BackgroundAdenosine-free indexes (AFIs), including resting Pd/Pa, instantaneous wave-free ratio (iFR) and contrast-FFR (cFFR), have been proposed to circumvent the use of vasodilators, in order to simplify the functional evaluation of coronary stenoses. Aims of this study were to analyze the correlation between AFIs and Fractional Flow Reserve (FFR) and to compare their diagnostic accuracy when FFR is used as reference. MethodsWe conducted a systematic review and meta-analysis of observational studies in which AFIs were compared to FFR. We produced paired forest plots to show the variation of the sensitivity and specificity estimates. We used a hierarchical summary ROC model (HSROC) to summarize the sensitivity and specificity of AFIs in detecting the concordance with FFR assessment. ResultsEighteen studies were included in this meta-analysis. Overall, 4424, 4822 and 2021 coronary lesions in 4410, 4472 and 1898 patients, respectively, were evaluated by Pd/Pa, iFR and cFFR, respectively. The overall Pearson's correlations were 0.81 (95%CI 0.78–0.83), 0.80 (95%CI 0.78–0.81) and 0.92 (95%CI 0.90–0.94) for Pd/Pa, iFR and cFFR, respectively. cFFR showed a significantly higher correlation with FFR compared to Pd/Pa and iFR (p < 0.0001). The area under the HSROC estimating the discriminating accuracy of cFFR was 0.95 (95%CI 0.94–0.96) and it was significantly higher compared to Pd/Pa (0.86, 95%CI 0.80–0.93) and iFR (0.89, 95%CI 0.84–0.94) (p < 0.0001). ConclusionsAFIs show a good correlation with the gold standard FFR. Among AFIs, cFFR shows the highest correlation with FFR and the best diagnostic accuracy.

Non-invasive functional assessment of coronary stenosis by cardiac computed tomography

The increased number of patients with coronary artery disease (CAD) is of great clinical relevance and involves a large burden of the healthcare system. The management of these patients is focused on relieving symptoms and improving clinical outcomes. Therefore, the ideal test would provide the correct diagnosis and actionable information. To this aim, several non-invasive functional imaging modalities are usually used as gatekeeper to invasive coronary angiography, but their diagnostic performance remains low with limited accuracy when compared to obstructive CAD at the time of invasive coronary angiography or invasive fractional flow reserve (FFR) assessment. For these reasons, an urgent need for non-invasive techniques that evaluate both the functional and morphological severity of CAD is growing. Coronary computed tomography angiography (CCTA) has emerged as a unique non-invasive technique providing coronary artery anatomic imaging. More recently, the evaluation of FFR with CCTA (FFRCT) has demonstrated high diagnostic performance compared to invasive FFR. Moreover, this tool has been proven to be more cost-effective than standard diagnostic pathways in large prospective multicenter trials, and to have a prognostic role. Additionally, stress myocardial computed tomography perfusion (stress CTP) represents a novel tool for the diagnosis of ischemia with high diagnostic accuracy. With advances in technical development, both static and dynamic computed tomography myocardial perfusion protocols offer functional assessment with an acceptable increase in radiation exposure. Compared to other imaging techniques, both FFRCT and stress CTP allow the combination of the anatomical evaluation of coronary arteries and the functional relevance of coronary artery lesions, having the potential to revolutionize the diagnostic paradigm of suspected CAD. FFRCT and stress CTP should be integrated in diagnostic pathways of patients with stable CAD and will likely result in a decrease of invasive diagnostic procedures and costs.

TCT-231 An artificial intelligence based solution for fully automated cardiac phase and end-diastolic frame detection on coronary angiographies

Invasive angiography is the gold standard in coronary artery imaging. Anatomical and non-invasive functional assessment of coronary stenoses is performed on end-diastolic angiographic frames (EDF), when coronary artery motion is minimal. We evaluate the performance of a workflow based on deep neural

Contrast Fractional Flow Reserve (cFFR): A pragmatic response to the call for simplification of invasive functional assessment

AimTo review the current approaches to simplify functional assessment of coronary stenosis with particular regard for contrast Fractional Flow Reserve (cFFR). Methods and resultsMaximal hyperaemia to assess FFR is perceived as time-consuming, costly, unpleasant for the patient and associated with side effects. Resting indexes, like Pd/Pa and iFR, have been proposed to circumvent the use of vasodilators as well as an approach based on the administration of contrast medium to induce coronary vasodilation, the cFFR. Contrast FFR can be obtained quickly, at very low cost in the absence of substantial side effects. Among these alternative indexes, cFFR shows the best correlation with FFR, reduces the use of adenosine even more than a hybrid resting approach but has not yet been tested in a randomized, controlled trial with clinical end-points. ConclusioncFFR represents a cheap, safe and effective alternative to FFR, able to facilitate the dissemination of a functional approach to myocardial revascularization.

Influence of Microcirculatory Dysfunction on Angiography-Based Functional Assessment of Coronary Stenoses

ObjectivesThe authors sought to evaluate the influence of coronary microcirculatory dysfunction (CMD) on the diagnostic performance of the quantitative flow ratio (QFR). BackgroundFunctional angiographic assessment of coronary stenoses based on fluid dynamics, such as QFR, constitutes an attractive alternative to fractional flow reserve (FFR). However, it is unknown whether CMD affects the reliability of angiography-based functional indices. MethodsFFR and the index of microcirculatory resistance (IMR) were measured in 300 vessels (248 patients) as part of a multicenter international registry. QFR was calculated at a blinded core laboratory. Vessels were classified into 2 groups according to microcirculatory status: low IMR (<23 U), and high IMR (≥23 U, CMD). The impact of CMD on the diagnostic performance of QFR, as well as on incremental value of QFR over quantitative angiography, was assessed using FFR as reference. ResultsPercent diameter stenosis (%DS) and FFR were similar in low- and high-IMR groups (%DS 51 ± 12% vs. 53 ± 11%; p = 0.16; FFR 0.80 ± 0.11 vs. 0.81 ± 0.11; p = 0.23, respectively). In the overall cohort, classification agreement (CA) between QFR and FFR and diagnostic efficiency of QFR (area under the receiver-operating characteristics curve [AUC]) were high (CA: 88%; AUC: 0.93 [95% confidence interval (CI): 0.90 to 0.96]). However, when assessed according to microcirculatory status, a significantly lower CA and AUC of QFR were found in the high-IMR group as compared with the low-IMR group (CA: 76% vs. 92%; p < 0.001; AUC: 0.88 [95% CI: 0.79 to 0.94] vs. 0.96 [95% CI: 0.92 to 0.98]; p < 0.05). Compared with angiographic assessment, QFR increased by 0.20 (p < 0.001) and by 0.16 (p < 0.001) the AUC of %DS in low- and high-IMR groups, respectively. Independent predictors of misclassification between QFR and FFR were high IMR and acute coronary syndrome. ConclusionsCMD decreases the diagnostic performance of QFR. However, even in the presence of CMD, QFR remains superior to angiography alone in ascertaining functional stenosis severity.

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

BackgroundAccurate 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 (FFRCT) for functional measurement of stenosis. However, the accuracy of FFRCT 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.MethodsInstead 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.ResultsThe 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).ConclusionThe 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.

Virtual Functional Assessment of Coronary Stenoses Using Intravascular Ultrasound Imaging: A Proof-of-Concept Pilot Study

We aimed to investigate the performance of virtual functional assessment of coronary stenoses using intravascular ultrasound (IVUS)-based three-dimensional (3D) coronary artery reconstruction against the invasively measured fractional flow reserve (FFR). Twenty-two (22) patients with either typical symptoms of stable angina or a positive stress test, who underwent IVUS and FFR, were included in this study. Five (5) patients presented FFR values lower than the 0.80 threshold, indicating ischaemia. IVUS-based 3D reconstruction and blood flow simulation were performed and the virtual functional assessment index (vFAI) was calculated. A strong correlation between IVUS-based vFAI and FFR was observed (Spearman correlation coefficient [rs]=0.88, p<0.0001). There was a small overestimation of the FFR by the IVUS-based vFAI (mean difference=0.0196±0.037; p=0.023 for difference from zero). All cases with haemodynamically significant stenoses (FFR≤0.8) were correctly categorised by the IVUS-based vFAI (vFAI≤0.8). The proposed approach allows the complete and comprehensive assessment of coronary stenoses providing anatomic and physiologic information, pre- and post-intervention, using only an IVUS catheter without the use of a pressure wire.

TCT-716 Functional assessment of coronary stenosis: Relationship between adenosine-free indexes and FFR

In this Study we evaluated the relationship and correlation between three adenosine-free indexes (Pd/Pa); contrast FFR (cFFR) and Pd/Pa after intracoronary nitroglycerine (0.2 mg) and 3cc of contrast (Pd/Pa-NTG-C) and fractional flow reserve with adenosine (FFR). We conducted a multicenter

Fractional flow reserve: a practical guide for interventional cardiologists and the cardiologist's point of view

Fractional flow reserve (FFR) is considered the gold standard for functional assessment of coronary stenosis in stable coronary artery disease. The use of FFR enables an ischemia-guided revascularization with improvement of clinical outcomes in a cost-effective fashion. Both clinical and interventional cardiologists should be aware of the advantages and potential pitfalls of this technique. We focus on FFR with the aim to provide the clinical cardiologist with information on indications and technical aspects to confirm a correct execution of FFR in different coronary anatomical settings.

Hybrid Instantaneous Wave-Free Ratio-Fractional Flow Reserve versus Fractional Flow Reserve in the Real World.

The instantaneous wave-free ratio (iFR) is a novel method to assess the ischemic potential of coronary artery stenoses. Clinical trial data have shown that iFR has acceptable diagnostic agreement with fractional flow reserve (FFR), the reference standard for the functional assessment of coronary stenoses. This study compares iFR measurements with FFR measurements in a real world, single-center setting. Instantaneous wave-free ratio and FFR were measured in 50 coronary artery lesions in 42 patients, with FFR ≤ 0.8 classified as functionally significant. An iFR-only technique, using a treatment cut-off value, iFR ≤ 0.89, provided a classification agreement of 84% with FFR ≤ 0.80. Use of a hybrid iFR-FFR technique, incorporating FFR measurement for lesions within the iFR gray zone of 0.86-0.93, would improve classification agreement with FFR to 94%, with diagnosis achieved without the need for hyperemia in 57% patients. This study in a real-world setting demonstrated good classification agreement between iFR and FFR. Use of a hybrid iFR-FFR technique would achieve high diagnostic accuracy while minimizing adenosine use, compared with routine FFR.

Assessing Computational Fractional Flow Reserve From Optical Coherence Tomography in Patients With Intermediate Coronary Stenosis in the Left Anterior Descending Artery.

Intravascular optical coherence tomography (OCT) imaging provides limited information on the functional assessment of coronary stenosis. We evaluated a new approach to OCT image-based computation modeling, which can be used to estimate the fractional flow reserve (FFR) in patients with intermediate coronary stenosis. Ninety-two patients with intermediate diameter stenosis in the left anterior descending artery underwent both FFR measurement with pressure wires and OCT examination. Using the OCT data, a computational fluid dynamics algorithm was used to calculate the computational FFR (FFROCT). The diagnostic performance of the FFROCT was assessed based on the pressure wire-based FFR. The median FFR and FFROCT values were 0.86 (0.79-0.89) and 0.89 (0.82-0.94), respectively. The average diameter stenosis in quantitative coronary angiography and area stenosis in OCT were 58.1±13.4% and 67.5±13.5%, respectively. The FFROCT was better correlated to the FFR than were the anatomic variables (r=0.72; P<0.001 versus r=0.46; P<0.001 for minimal luminal diameter on quantitative coronary angiography or r=0.57; P<0.001 for minimal lumen area on OCT). When functionally significant stenosis was defined as an FFR cutoff value of ≤0.8, FFROCT resulted in 88.0% accuracy, 68.7% sensitivity, and 95.6% specificity. The positive and negative predictive values were 84.2% and 89.0%, respectively. The computation of FFROCT enables assessment not only of anatomic information, but also of the functional significance of intermediate stenosis. This measurement may be a useful approach for the simultaneous evaluation of the functional and anatomic severity of coronary stenosis.

Fractional flow reserve (FFR) et instantaneous wave-free ratio (iFR), l’évaluation physiologique d’une sténose coronarienne dans le laboratoire de catéthérisme cardiaque : mise au point et guide pratique

In recent years, a large body of evidence has revealed the limitations of angiographic evaluation in determining the physiological significance of coronary stenosis, particularly when these are intermediate lesions. Percutaneous coronary interventions (PCI) guided by physiological assessment using fractional flow reserve (FFR) have been shown to reduce cardiovascular events when compared to angiography alone. Recently, another coronary physiologic parameter has been introduced: the “instantaneous wave-free ratio” (iFR). In this review, we will discuss the FFR, the iFR, and their use in the functional assessment of coronary stenosis in the cardiac catheterization laboratory. This review will cover theoretical aspects for non-interventional cardiologists, as well as practice points and common pitfalls related to coronary physiological assessment for interventional cardiologists.

Coronary computed tomography angiography for the assessment of chest pain: current status and future directions.

Chest pain is one of the most common presenting symptoms leading to presentation to medical clinics and Emergency Departments worldwide. Defining the nature and etiology of chest pain can pose a diagnostic dilemma for clinicians, despite the availability of several diagnostic algorithms and guidelines to assist them in evaluating these patients. Most investigations in patients with acute chest pain are initially performed to either exclude or diagnose and manage potentially life-threatening conditions such as acute coronary syndrome, pulmonary embolism and aortic dissection. In cases of stable chest pain syndromes, the focus shifts to determining the presence, extent and severity of coronary artery disease. In recent years, coronary computed tomography angiography (CCTA) is being increasingly used worldwide in the assessment of both stable and acute chest pain syndromes. This review evaluates the current evidence regarding the clinical utility of CCTA in the stable and acute chest pain settings and outlines the latest advances in CCTA techniques, including functional assessment of coronary stenoses, and their potential clinical application to improve patient care in a cost-effective manner.

Current and Novel Imaging Techniques in Coronary CT.

Multidetector coronary computed tomography (CT), which is widely performed to assess coronary artery disease noninvasively and accurately, provides excellent image quality. Use of electrocardiography (ECG)-controlled tube current modulation and low tube voltage can reduce patient exposure to nephrotoxic contrast media and carcinogenic radiation when using standard coronary CT with a retrospective ECG-gated helical scan. Various imaging techniques are expected to overcome the limitations of standard coronary CT, which also include insufficient spatial and temporal resolution, beam-hardening artifacts, limited coronary plaque characterization, and an inability to allow functional assessment of coronary stenosis. Use of a step-and-shoot scan, iterative reconstruction, and a high-pitch dual-source helical scan can further reduce radiation dose. Dual-energy CT can improve contrast medium enhancement and reasonably reduce the contrast dose when combined with noise reduction with the use of iterative reconstruction. High-definition CT can improve spatial resolution and diagnostic evaluation of small or peripheral coronary vessels and coronary stents. Dual-source CT and a motion correction algorithm can improve temporal resolution and reduce coronary motion artifacts. Whole-heart coverage with 320-detector CT and an intelligent boundary registration algorithm can eliminate stair-step artifacts. By decreasing beam hardening and enabling material decomposition, dual-energy CT is expected to remove or reduce the depiction of coronary calcification to improve intraluminal evaluation of calcified vessels and to provide detailed analysis of coronary plaque components and accurate qualitative and quantitative assessment of myocardial perfusion. Fractional flow reserve derived from coronary CT is a state-of-the-art noninvasive technique for accurately identifying myocardial ischemia beyond coronary CT. Understanding these techniques is important to enhance the value of coronary CT for assessment of coronary artery disease.

Numerical Validation of Diagnostic Uncertainties During In Vitro Assessment of Serial Coronary Stenoses

Fractional flow reserve (FFR: ratio of pressures distal and proximal to a stenosis), the commonly used diagnostic parameter for functional assessment of coronary stenosis, has a threshold range of 0.75–0.80 below which clinical intervention is recommended. This range is known as a “gray” zone resulting in uncertainty of diagnosis. An alternate diagnostic parameter, pressure drop coefficient (CDP: ratio of trans-stenotic pressure drop to the proximal dynamic pressure), developed based on fundamental fluid dynamics principles, has been suggested by our group. Pressure drop coefficient has a wide range of

TCT-631 Low coronary microcirculatory resistance associated to profound hypotension during intravenous adenosine infusion. Implications for the functional assessment of coronary stenoses.

TCT-631 Low coronary microcirculatory resistance associated to profound hypotension during intravenous adenosine infusion. Implications for the functional assessment of coronary stenoses.

A novel way to induce coronary hyperaemia

Coronary angiography and measurement of fractional flow reserve (FFR) are used for anatomical and functional assessment of coronary stenoses. The achievement of maximal coronary hyperaemia is crucial for an accurate calculation of FFR. Although adenosine and papaverine have been well validated, their mechanisms of action as well as methods of administration have some limitations. New and better agents to induce hyperaemia are therefore still being sought. Currently regadenoson, a selective adenosine A2A receptor agonist, seems to possess the characteristics of the almost ‹ideal› hyperaemic stimulus.

Fractional flow reserve as the reference standard for myocardial perfusion studies: fool's gold?

The evidence for the use of cardiovascular magnetic resonance (CMR) as a first-line diagnostic tool in patients with suspected coronary artery disease (CAD) has been solidified by the recent publication of large clinical studies and meta-analyses.1–3 Most of this evidence has been gathered against anatomical angiographic endpoints, despite the well-known fact that luminal stenosis correlates poorly with haemodynamic significance, particularly for coronary stenoses between 30 and 80% of luminal diameter.4,5 Multiple factors, such as entrance effects, friction, and turbulence, can contribute to coronary blood flow resistance and the loss of pressure across a stenosis, and therefore the haemodynamic significance of lesions can be underappreciated by two-dimensional angiographic images, particularly in the setting of eccentric or irregular stenoses.6 In clinical practice, coronary angiography is therefore often complemented by non-invasive imaging tests to determine the functional significance of a borderline stenosis and guide patient management. Recent clinical practice guidelines for revascularization recommend a combination of anatomical and ischaemia testing for most clinical scenarios.7 Invasive pressure-wire-derived fractional flow reserve (FFR) has become a popular alternative for the functional assessment of coronary stenosis that can be performed in the catheter laboratory. FFR is calculated as the ratio of maximal blood flow in a stenotic artery relative to maximal flow in the same artery in the theoretic absence of any stenosis.8–11 In recent years, …

Functional assessment of coronary stenoses: can we live without it?

When selecting coronary stenoses for interventional treatment, assessment of reversible ischaemia is paramount from a symptomatic as well as prognostic point of view. Fractional flow reserve (FFR) is now considered the gold standard for invasive assessment of ischaemia. By measuring FFR in the catheterization laboratory, one can accurately identify which lesions should be stented resulting in improved patient outcome in most elective clinical and angiographic conditions. Recently, in the European Society of Cardiology guidelines on coronary revascularization, FFR was upgraded to an IA classification in multivessel percutaneous coronary intervention. In this review paper, the rationale for routine measurement of FFR will be reviewed and studies supporting its integration into everyday practice will be highlighted.