Determining the haemodynamic significance of arterial stenosis: the relationship between CT angiography, computational fluid dynamics, and non-invasive fractional flow reserve

Functional Coronary Artery Assessment: a Systematic Literature Review

Cardiovascular diseases represent the number one cause of death in the world, including the most common disorders in the heart's health, namely coronary artery disease (CAD). CAD is mainly caused by fat accumulated in the arteries' internal walls, creating an atherosclerotic plaque that impacts the blood flow functional behavior. Anatomical plaque characteristics are essential but not sufficient for a complete functional assessment of CAD. In fact, plaque analysis and visual inspection alone have proven insufficient to determine the lesion severity and hemodynamic repercussion. Furthermore, the fractional flow reserve (FFR) exam, which is considered the gold standard for stenosis functional impair determination, is invasive and contains several limitations. Such a panorama evidences the need for new techniques applied to image exams to improve CAD functional assessment. In this article, we perform a systematic literature review on emerging methods determining CAD significance, thus delivering a unique base for comparing these methods, qualitatively and quantitatively. Our goal is to guide further studies with evidence from the most promising methods, highlighting the benefits from both areas. We summarize benchmarks, metrics for evaluation, and challenges already faced, thus shedding light on the requirements for a valid, meaningful, and accepted technique for functional assessment evaluation. We create a base of comparison based on quantitative and qualitative indicators and highlight the most relevant geometrical metrics that correlate with lesion significance. Finally, we point out future benchmarks based on recent literature.

Numerical Study of the Blood Flow in a Deformable Human Aorta

In this work, we present a numerical investigation of blood flow in a portion of the human vascular system. More precisely, the present work analyzed the blood flow in the upper portion of the aorta. The aorta and its ramified blood vessels are surrounded by the cardiac muscle. The blood flow generates pressure on the internal surfaces of the artery and its ramifications, thereby causing deformation of the cardiac muscle. The numerical analysis used the Navier–Stokes equations as the governing equations of blood flow for the calculation of the velocity field and pressure distribution in the blood. The neo-Hookean hyperelastic model was used for the description of the behavior of the vessel walls. The velocity and pressure distributions were analyzed. The deformation of the vessel was also investigated. The numerical results could be used to better understand and predict the factors that trigger cardiovascular diseases and distortions of the aorta and as a diagnostic tool in clinical applications.

The challenge of asymptomatic coronary artery disease in aircrew; detecting plaque before the accident

Coronary events remain a major cause of sudden incapacitation, including death, in both the general population and among aviation personnel, and are an ongoing threat to flight safety and operations. The presentation is often unheralded, especially in younger adults, and is often due to rupture of a previously non-obstructive coronary atheromatous plaque. The challenge for aeromedical practitioners is to identify individuals at increased risk for such events. This paper presents the NATO Cardiology Working Group (HFM 251) consensus approach for screening and investigation of aircrew for asymptomatic coronary disease.A three-phased approach to coronary artery disease (CAD) risk assessment is recommended, beginning with initial risk-stratification using a population-appropriate risk calculator and resting ECG. For aircrew identified as being at increased risk, enhanced screening is recommended by means of Coronary Artery Calcium Score alone or combined with a CT coronary angiography investigation. Additional screening may include exercise testing, and vascular ultrasound imaging. Aircrew identified as being at high risk based on enhanced screening require secondary investigations, which may include functional ischaemia, and potentially invasive coronary angiography. Functional stress testing as a stand-alone investigation for significant CAD is not recommended in aircrew. Aircrew identified with coronary disease require further clinical and aeromedical evaluation before being reconsidered for flying status.

FFRCT derived from computed tomography angiography: the experience in the UK

INTRODUCTION

Non-invasive fractional flow reserve derived from CT coronary angiography (FFR_CT) represents a novel technology to investigate coronary artery disease. The application of computational flow dynamics to anatomical data provides the clinician with a further functional assessment to inform decision-making in patients with coronary artery disease. In the UK FFR_CT has received medical technology approval for use since February 2017. Areas covered: This article discusses the mathematical and physiological principles underpinning calculation of non-invasive fractional flow reserve (FFR), as well as discussing the differences between the commercially available technologies. Diagnostic accuracy, cost effectiveness and safety of non-invasive FFR from the early clinical trials is examined. Further to this the potential implications of the use of non-invasive FFR in clinical practice in the UK are discussed. Expert commentary: Non-invasive FFR represents a promising comprehensive imaging technology providing both anatomical and physiological data to accurately diagnose obstructive coronary artery disease. The technology has yet to prove to be cost effective in 'real world' cohorts before becoming integrated into everyday clinical practice and guidelines in the United Kingdom.

Radical changes to the investigation of stable chest pain following the 2016 NICE update

The 2016 National Institute for Health and Care Excellence (NICE) guidelines mark a radical change in the diagnosis of patients with stable chest pain. Quantitative assessments of the disease probability are no longer considered necessary to determine the need and type of diagnostic testing. Instead, the recommendation is for no diagnostic test if the chest pain is judged to be "non-anginal" and CT coronary angiography (CTCA) in patients with "typical" or "atypical" chest pain. The new emphasis on anatomical, rather than functional testing is driven by the accuracy, safety and cost effectiveness of the different investigations as evaluated by NICE. Despite inevitable resource implications NICE calculates that annual savings will be significant.

CT Determination of Fractional Flow Reserve in Coronary Lesions

Invasively determined fractional flow reserve (FFR) represents the gold-standard method for the functional evaluation of coronary lesions. Coronary computed tomography angiography (CCTA) provides characterization of the coronary anatomy, with important morphological information on the atherosclerotic plaques, but does not offer a hemodynamic evaluation of coronary artery lesions. CT evaluation of FFR (FFRCT) is a new noninvasive diagnostic method, which provides anatomical and functional assessment of the whole coronary tree, based on computational techniques, with no more radiation or hyperemic agent administration compared with routine CCTA. Recent studies demonstrated the safety and accuracy of FFRCT and its therapeutic use and cost benefits in real-world clinical use.

Noninvasive Assessment of Coronary Artery Disease: Fractional Flow Reserved Derived from Coronary Computed Tomography Angiography (FFRCT)

Invasive coronary angiography (ICA) completed by fractional flow reserve (FFR) assessment represents the main procedure that is performed in the decision process for coronary revascularization. Coronary Computed Tomography Angiography (CCTA) is an effective method used in the noninvasive anatomic assessment of coronary artery disease (CAD). However, CCTA tends to overestimate and does not offer hemodynamic data about the coronary lesions. Recent progresses made in the research involving computational fluid dynamics and image modeling permit the evaluation of FFRCT noninvasively, using data obtained in a standard CCTA. Studies have shown an improved precision and discrimination of FFRCT compared to CCTA for the diagnosis of significant coronary artery stenosis. In this review, we aimed to summarize the role of CCTA in CAD evaluation, the impact of FFRCT, the scientific basis of this novel method and its potential clinical applications.