Is the Anatomy the New Paradigm in the Chronic Coronary Syndromes?

Abstract

Address for reprints: chrcaroli@gmail.com The condition widely known as chronic stable angina used to be considered as uncomplicated and generally easy to solve by percutaneous revascularization. However, this is no longer the case. Understanding of its true significance has evolved towards characterizing different pathophysiological forms currently and widely known as chronic coronary syndromes (CCS). This paper intends to briefly describe the most relevant data from the latest evidence and to reflect on the meaning of myocardial ischemia when making clinical decisions about revascularization in the year 2023. We need to distinguish at least 4 subtypes of CCS: severe left main coronary artery (LMCA) lesion/severe proximal multivessel lesions; severe diffuse multivessel disease; severe focal lesion; and non-severe diffuse disease/without angiographically significant lesions, with microcirculation involvement. These are all synonyms of atherosclerosis and vascular dysfunction with considerable overlapping. The role of clinical cardiology is to be able to include the patient in the right part of the spectrum in order to maximize the treatment benefits. This analysis will not include microvascular disease with no significant epicardial lesions, as it demands a different approach. Concisely, evaluation ideally involves invasive tests of coronary physiology, including an acetylcholine test to rule out epicardial (and microcirculation) vasospasm, as well as the calculation of the coronary flow reserve and the microcirculatory resistance index. Furthermore, if a non-invasive evaluation is chosen, quantification of the absolute flow via a cardiac positron emission tomography (PET) is the most informative test. (1,2) Another possibility is the semiquantitative evaluation provided by the stress ECG through the anterior descending artery flow reserve. Please note that an abnormal flow reserve cannot be ruled out by absence of myocardial ischemia on a “conventional” single photon emission computed tomography (SPECT) or a stress echo. (3) Further understanding of ischemic heart disease has increased, and the paradigm is changing again. From the anatomy to the ischemia, a little more than two decades have passed, ¿and now from the ischemia to the anatomy again? As reflected by the guidelines from nearly all scientific associations, a short time ago, (4,5) the presence of myocardial ischemia ≥10% was considered as high-risk for events and was an unquestioned cut-off point when deciding on an invasive revascularization strategy for chronic coronary disease. Ischemia was the focus of every decision. This outdated concept has been updated by the extensive observational study performed by Dr. Rory Hachamovitch et al. from Cedars-Sinai Medical Center and published in Circulation in 2003, which included more than 10 300 patients. (6) With all the evidence and data from the ISCHEMIA study, one question shocked the clinical scenario three years ago: has significant ischemia ceased to be a sine qua non sign of revascularization, even with symptoms present? The answer was yes. Why? Essentially because we have observed that “sustained long-term intensive” drug therapy has shown clinical efficacy and safety to the detriment of an invasive approach. Why? There is no simple answer to this question, but we could easily mention the following: stabilized (or even reduced) plaque with the resulting clinical and imaging slowdown in disease progression, myocardial protection, vascular function improvement, and symptom control. A healthy lifestyle (7) (exercise, a Mediterranean diet, avoidance of smoking, and stress control), a goal-directed therapy [angiotensin converting enzyme inhibitors/angiotensin receptor blockers, (7) β-blockers, (8) statins, (9) ezetimibe, (10) and PCSK9 inhibitors], and an eventually improved antithrombotic management, apart from aspirin in high-risk patients [P2Y12 receptor blockers (11) and antiXa-rivaroxaban (12,13)], have shown the strengths of selecting a conservative therapy. In addition, a deeper understanding of coronary circulation pathophysiology has introduced new concepts in clinical cardiology, such as coronary flow reserve (CFR), which has become a major prognostic