Acute Coronary Syndrome (ACS)

How to Cite This Chapter: Jolly SS, Mulloy A, Kelly A, Budaj A, Bednarz B, Leśniak W. Acute Coronary Syndrome (ACS). McMaster Textbook of Internal Medicine. Kraków: Medycyna Praktyczna. Accessed January 22, 2021.
Last Updated: July 8, 2019
Last Reviewed: July 8, 2019
Chapter Information

Acute coronary syndrome (ACS) is a clinical syndrome of acute chest pain related to acute myocardial ischemia. ACS is classified based on electrocardiography (ECG) results into ST-segment elevation ACS and non–ST-segment elevation ACS. This approach has important practical implications because patients presenting with ST-segment elevation ACS require immediate reperfusion therapy.

Definition Top

Classification of ACS: see Ischemic Heart Disease.

Definition of myocardial infarction: see Table 3.11-1.

1. Non–ST-segment elevation ACSs (unstable angina [UA]/non–ST-segment elevation myocardial infarction [NSTEMI]) are caused by acute myocardial ischemia that in some patients leads to myocardial necrosis manifested by elevated serum markers of myocardial necrosis without an acute ST-segment elevation seen on ECG. Patients with UA/NSTEMI constitute a heterogeneous group due to the complex pathogenesis, which includes atherosclerotic plaque rupture with superimposed thrombosis, progressive obstruction of a coronary artery, arterial constriction, inadequate oxygen supply relative to myocardial demand, or spontaneous coronary dissection.

2. ST-segment elevation myocardial infarction (STEMI) is a clinical syndrome usually caused by the cessation of blood flow through a coronary artery due to its occlusion, which results in transmural ischemia leading to ST-segment elevation and typically myocardial necrosis manifested by increased blood levels of specific biomarkers.

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