Practical Application of Coronary Physiologic Assessment: Asia-Pacific Expert Consensus Document: Part 1.

Coronary physiologic assessment is performed to measure coronary pressure, flow, and resistance or their surrogates to enable the selection of appropriate management strategy and its optimization for patients with coronary artery disease. The value of physiologic assessment is supported by a large body of evidence that has led to major recommendations in clinical practice guidelines. This expert consensus document aims to convey practical and balanced recommendations and future perspectives for coronary physiologic assessment for physicians and patients in the Asia-Pacific region based on updated information in the field that including both wire- and image-based physiologic assessment. This is Part 1 of the whole consensus document, which describes the general concept of coronary physiology, as well as practical information on the clinical application of physiologic indices and novel image-based physiologic assessment.

Practical Application of Coronary Physiologic Assessment: Asia-Pacific Expert Consensus Document: Part 2.

Coronary physiologic assessment is performed to measure coronary pressure, flow, and resistance or their surrogates to enable the selection of appropriate management strategy and its optimization for patients with coronary artery disease. The value of physiologic assessment is supported by a large body of clinical data that has led to major recommendations in all practice guidelines. This expert consensus document aims to convey practical and balanced recommendations and future perspectives for coronary physiologic assessment for physicians and patients in the Asia-Pacific region, based on updated information in the field that includes both wire- and image-based physiologic assessment. This is Part 2 of the whole consensus document, which provides theoretical and practical information on physiologic indexes for specific clinical conditions and patient statuses.

Consensus document for invasive coronary physiologic assessment in Asia-Pacific countries.

BACKGROUND: Currently, invasive physiologic assessment such as fractional flow reserve is widely used worldwide with different adoption rates around the globe. Patient characteristics and physician preferences often differ in the Asia-Pacific (APAC) region with respect to treatment strategy, techniques, lesion complexity, access to coronary physiology and imaging devices, as well as patient management. Thus, there is a need to construct a consensus document on recommendations for use of physiology-guided percutaneous coronary intervention (PCI) in APAC populations. This document serves as an overview of recommendations describing the best practices for APAC populations to achieve more consistent and optimal clinical outcomes. METHODS AND RESULTS: A comprehensive multiple-choice questionnaire was provided to 20 interven- tional cardiologists from 10 countries in the APAC region. Clinical evidence, tips and techniques, and clinical situations for the use of physiology-guided PCI in APAC were reviewed and used to propose key recommendations. There are suggestions to continue to develop evidence for lesion and patient types that will benefit from physiology, develop directions for future research in health economics and local data, develop appropriate use criteria in different countries, and emphasize the importance of education of all stakeholders. A consensus recommendation to enhance the penetration of invasive physiology-based therapy was to adopt the 5E approach: Evidence, Education, Expand hardware, Economics and Expert consensus. CONCLUSIONS: This consensus document and recommendations support interventional fellows and cardiologists, hospital administrators, patients, and medical device companies to build confidence and encourage wider implementation of invasive coronary physiology-guided therapy in the APAC region.

Haemodynamic assessment of human coronary arteries is affected by degree of freedom of artery movement.

Abnormal haemodynamic parameters are associated with atheroma plaque progression and instability in coronary arteries. Flow recirculation, shear stress and pressure gradient are understood to be important pathogenic mediators in coronary disease. The effect of freedom of coronary artery movement on these parameters is still unknown. Fluid-structure interaction (FSI) simulations were carried out in 25 coronary artery models derived from authentic human coronaries in order to investigate the effect of degree of freedom of movement of the coronary arteries on flow recirculation, wall shear stress (WSS) and wall pressure gradient (WPG). Each FSI model had distinctive supports placed upon it. The quantitative and qualitative differences in flow recirculation, maximum wall shear stress (MWSS), areas of low wall shear stress (ALWSS) and maximum wall pressure gradient (MWPG) for each model were determined. The results showed that greater freedom of movement was associated with lower MWSS, smaller ALWSS, smaller flow recirculation zones and lower MWPG. With increasing percentage diameter stenosis (%DS), the effect of degree of freedom on flow recirculation and WSS diminished. Freedom of movement is an important variable to be considered for computational modelling of human coronary arteries, especially in the setting of mild to moderate stenosis. ABBREVIATIONS: 3D: Three-dimensional; 3DR: Three-dimensional Reconstruction; 3D-QCA: Three-dimensional quantitative coronary angiography; ALWSS: Areas of low wall shear stress; CAD: Coronary artery disease; CFD: Computational fluid dynamics; %DS: Diameter stenosis percentage; EPCS: End point of counter-rotating streamlines; FSI: Fluid-structure interaction; IVUS: Intravascular ultrasound; LAD: Left anterior descending; MWSS: Maximum wall shear stress; SST: Shear stress transport; TAWSS: Time-averaged wall shear stress; WSS: wall shear stress; WPG: Wall pressure gradient; MWPG: Maximum wall pressure gradient; FFR: Fractional flow reserve; iFR: Instantaneous wave-free ratio.

Percutaneous Transcatheter Assessment of the Left Main Coronary Artery: Current Status and Future Directions.

Accurate assessment of the left main coronary artery (LMCA) is critical in determining treatment strategies and delineating revascularization options to improve prognosis. There has been an evolution in invasive techniques that allow detailed assessment of both function and anatomy. As technologies advance, there is an increasing amount of evidence supporting the use of percutaneous coronary intervention for the LMCA. This state-of-the-art paper provides an in-depth exploration of intravascular ultrasound, fractional flow reserve, and optical coherence tomography. A discussion is provided that explores the basis for application of these technologies, the body of evidence for each modality and its use in LMCA assessment, and the potential role in post-PCI optimization in what is a dynamically changing field.

The index of microcirculatory resistance in the physiologic assessment of the coronary microcirculation.

The coronary microcirculation plays a critical role in normal cardiac physiology as well as in many disease states. However, methods to evaluate the function of the coronary microvessels have been limited by technical and theoretical issues. Recently, the index of microcirculatory resistance (IMR) has been proposed and validated as a simple and specific invasive method of assessing the coronary microcirculation. By relying on the thermodilution theory and using a pressure-temperature sensor guidewire, IMR provides a measurement of the minimum achievable microcirculatory resistance in a target coronary artery territory, enabling a quantitative assessment of the microvascular integrity. Unlike indices such as coronary flow reserve, IMR is highly reproducible and independent of hemodynamic changes. In ST-elevation myocardial infarction, IMR predicts myocardial recovery and long-term mortality, whereas in patients with stable coronary artery disease, preintervention IMR predicts the occurrence of periprocedural myocardial infarction. Increasingly, research has focused on IMR-guided interventions of the microcirculation, with the aim of preventing and/or treating the microcirculatory dysfunction that commonly accompanies the epicardial coronary disease. In the present review, we will discuss the theoretical and practical basis for IMR, the clinical studies supporting it, and the future lines of research using this novel tool.

Fractional flow reserve assessment of left main stenosis in the presence of downstream coronary stenoses.

BACKGROUND: Several studies have shown that fractional flow reserve (FFR) measurement can aid in the assessment of left main coronary stenosis. However, the impact of downstream epicardial stenosis on left main FFR assessment with the pressure wire in the nonstenosed downstream vessel remains unknown. METHODS AND RESULTS: Variable stenoses were created in the left main coronary arteries and downstream epicardial vessels in 6 anaesthetized male sheep using balloon catheters. A total of 220 pairs of FFR assessments of the left main stenosis were obtained, before and after creation of a stenosis in a downstream epicardial vessel, by having a pressure-sensor wire in the other nonstenosed downstream vessel. The apparent left main FFR in the presence of downstream stenosis (FFR(app)) was significantly higher compared with the true FFR in the absence of downstream stenosis (FFR(true); 0.80±0.05 versus 0.76±0.05; estimate of the mean difference, 0.035; P<0.001). The difference between FFR(true) and FFR(app) correlated with composite FFR of the left main plus stenosed artery (r=-0.31; P<0.001) indicating that this difference was greater with increasing epicardial stenosis severity. Among measurements with FFR(app) >0.80, 9% were associated with an FFR(true) of <0.75. In all instances, the epicardial lesion was in the proximal portion of the stenosed vessel, and the epicardial FFR (combined FFR of the left main and downstream stenosed vessel) was ≤0.50. CONCLUSIONS: A clinically relevant effect on the FFR assessment of left main disease with the pressure wire in a nonstenosed downstream vessel occurs only when the stenosis in the other vessel is proximal and very severe.