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Hot topics in ischaemic heart disease: revascularization, hibernation, type 2 infarction, and proteomics.

This Focus Issue on ischaemic heart disease contains the State of the Art Review article ‘Invasive and non-invasive assessment of ischaemia in chronic coronary syndromes: translating pathophysiology to clinical practice’ by Ozan Demir from King’s College London in the UK, and colleagues. The authors point out that intracoronary physiology testing has emerged as a valuable diagnostic approach in the management of patients with chronic coronary syndrome, circumventing limitations such as inferring coronary function from anatomical assessment and low spatial resolution associated with angiography or non-invasive tests. The value of hyperaemic translesional pressure ratios to estimate the functional relevance of coronary stenoses is supported by a wealth of prognostic data. The continuing drive to further simplify this approach led to the development of nonhyperaemic pressure-based indices. Recent attention has focused on estimating physiology without even measuring coronary pressure. However, the reduction in procedural time and ease of accessibility afforded by these simplifications needto be counterbalanced against the increasing burden of physiological assumptions, which may impact on the ability to reliably identify an ischaemic substrate, the goal during catheter laboratory assessment. In that regard, measurement of both coronary pressure and flow enables comprehensive physiological evaluation of both epicardial and microcirculatory components of the vasculature, although widespread adoption has been hampered by perceived technical complexity and, in general, an underappreciation of the role of the microvasculature. In parallel, entirely non-invasive tools have matured, with the utilization of various techniques including computational fluid dynamic and quantitative perfusion analysis. This review article appraises the strengths and limitations of each test in investigating myocardial ischaemia and discusses a comprehensive algorithm that could be used to obtain a diagnosis in all patients with angina scheduled for coronary angiography, including those who are not found to have obstructive epicardial coronary disease. In another State of the Art Review article entitled ‘Myocardial viability testing: all STICHed up, or about to be REVIVED?’, Matthew Ryan from King’s College London in the UK, and colleagues note that patients with ischaemic left ventricular dysfunction frequently undergo myocardial viability testing. The historical model presumes that those who have extensive areas of dysfunctional yet viable myocardium derive particular benefit from revascularization, whilst those without extensive viability do not. These suppositions rely on the theory of hibernation and are based on data of low quality: taking a dogmatic approach may therefore lead to patients being refused appropriate, prognostically important treatment. Recent data from a substudy of the randomized STICH trial challenges these historical concepts, as the volume of viable myocardium failed to predict the effectiveness of coronary artery bypass grafting. Should the Heart Team now abandon viability testing, or are new paradigms needed in the way we interpret viability? This state of the art review critically examines the evidence base for viability testing, focusing on the presumed interactions between viability, functional recovery, revascularization, and prognosis which underly the traditional model. The authors consider whether viability should relate solely to dysfunctional myocardium or be considered more broadly and explore wider uses of viability testing outside of revascularization decision-making. Finally, they look forward to ongoing and future randomized trials, which will shape evidence-based clinical practice in the future. Whilst the risk factors for type 1 myocardial infarction due to atherosclerotic plaque rupture and thrombosis are established,