For over a century astute clinicians have recognized that prodromal symptoms often precede acute myocardial infarction (MI). The evolution of symptoms was subsequently found to correlate with changes in atherosclerotic plaque composition, morphology, and thrombogenicity, leading to the classification of symptoms that are currently categorized to better delineate diagnostic and management strategies. Acute coronary syndromes (ACSs) are traditionally divided into two separate categories—ST-segment elevation and non–ST-segment elevation ACS—based on the presenting electrocardiogram. The latter category is then subdivided into unstable angina and non–ST-segment elevation MI, based on the absence or presence of elevated cardiac biomarkers, respectively. This chapter considers ST-segment elevation MI and non–ST-segment elevation ACS based on pharmacologic and clinical (diagnostics and routine management) constructs. ST-segment elevation MI (STEMI), in a vast majority of cases, is caused by occlusive thrombosis at a site of plaque rupture. In others, particularly when the stimulus for thrombosis is strong, occlusion may follow minor disruption of the plaque surface (erosion) or occur in areas of endothelial cell injury (activation with inflammatory features and concomitantly impaired vascular thromboresistance). Coronary arterial spasm, in the absence of intrinsic vascular disease (as may be seen with cocaine use), can also impair restrictive blood flow to the myocardium, resulting in cellular death. The goal of pharmacology-based therapy (and mechanical intervention) is to restore myocardial blood flow as quickly and completely as possible. The “open vessel hypotheses” predicts that rapid, complete, and sustained myocardial perfusion through the prompt restoration of physiologic blood flow will minimize (salvage) myocardium, promote ventricular performance, and reduce mortality. Strong support for the open-vessel hypothesis can be traced to the Thrombolysis and Myocardial Infarction (TIMI) trial performed in the 1980s (Dalen et al., 1988; TIMI Study Group, 1985). Patients with patent infarct-related coronary arteries 90 minutes after the initiation of fibrinolytic therapy had an 8.1% mortality at 1 year, compared to a 14.8% mortality among those with an occluded vessel. Since that time, several large-scale clinical trials have confirmed the importance of an open infarct-related coronary artery for early, intermediate, and long-term outcome.
The IFCC Clinical Application of Cardiac Biomarkers Committee’s Appraisal of the 2020 ESC Guidelines for the Management of Acute Coronary Syndromes in Patients Presenting Without Persistent ST-segment Elevation: Getting Cardiac Troponin Right
