Acute Coronary Syndrome and Chest Pain
Acute coronary syndrome (ACS) and the broader presentation of acute chest pain are among the most common and highest-stakes problems in emergency medicine. This area covers how the emergency clinician approaches the patient with possible myocardial ischaemia: rapid risk stratification, electrocardiographic interpretation, cardiac biomarker testing, and the distinction between ST-elevation myocardial infarction and non-ST-elevation acute coronary syndromes.
Definition
Acute coronary syndrome is a spectrum of conditions caused by acute myocardial ischaemia, ranging from unstable angina through non-ST-elevation myocardial infarction to ST-elevation myocardial infarction; acute chest pain is the presenting symptom that prompts evaluation for ACS and a range of other cardiac and non-cardiac causes.
Scope
The area orients the reader to the diagnostic reasoning behind acute chest pain rather than to drug-specific or procedural management. It links the clinical entities (ACS, STEMI) with the principal diagnostic tools (the electrocardiogram and cardiac troponin) and the structured risk-assessment frameworks used to separate patients who need urgent reperfusion or admission from those who can be safely discharged. It is a reference and educational overview, not a treatment protocol.
Sub-topics
Core questions
- How does the emergency clinician distinguish ischaemic chest pain from non-cardiac causes?
- What role do the electrocardiogram and cardiac troponin play in the early diagnosis of acute coronary syndrome?
- How are patients with acute chest pain risk-stratified for adverse cardiac events?
- What separates ST-elevation myocardial infarction, which calls for immediate reperfusion, from non-ST-elevation acute coronary syndromes?
Key concepts
- Acute coronary syndrome spectrum (unstable angina, NSTEMI, STEMI)
- 12-lead electrocardiography
- Cardiac troponin and high-sensitivity assays
- Risk stratification (GRACE, HEART, TIMI scores)
- ST-segment elevation versus non-ST-elevation
- Universal definition of myocardial infarction
Mechanisms
Most acute coronary syndromes arise from rupture or erosion of an atherosclerotic plaque with superimposed thrombosis, producing a sudden mismatch between myocardial oxygen supply and demand. The degree and persistence of coronary occlusion determines the clinical and electrocardiographic picture: transmural, persistent occlusion typically produces ST-segment elevation and ongoing myocyte necrosis, whereas subtotal or transient occlusion produces non-ST-elevation syndromes detectable through cardiac biomarker release. The diagnostic approach therefore integrates the symptom history, the electrocardiogram, and serial troponin measurement.
Clinical relevance
Acute chest pain accounts for a large share of emergency department visits, and missed acute coronary syndrome is a recognised source of harm. The diagnostic frameworks described here explain how clinicians weigh symptoms, electrocardiographic findings, and biomarkers to estimate the probability of an acute coronary event. The material is educational and describes how evidence is generated and applied; it is not a substitute for clinical judgement or individualised care.
Epidemiology
Ischaemic heart disease is a leading cause of death worldwide, and acute coronary syndrome is a frequent reason for emergency presentation. Only a minority of patients presenting with chest pain ultimately have an acute coronary syndrome, which is why structured risk stratification and serial testing are central to the emergency evaluation.
Evidence & guidelines
Contemporary practice draws on major society guidelines, including the 2023 ESC Guidelines for the management of acute coronary syndromes (Byrne et al., 2023) and the 2021 AHA/ACC chest pain guideline (Gulati et al., 2021). The Fourth Universal Definition of Myocardial Infarction (Thygesen et al., 2018) standardises the biomarker and clinical criteria for infarction, and validated risk scores such as GRACE (Fox et al., 2006) support prognostication.
History
The emergency evaluation of chest pain evolved from reliance on the electrocardiogram and creatine kinase toward troponin-centred diagnosis, and the term 'acute coronary syndrome' came into wide use to capture the shared pathophysiology of plaque disruption underlying unstable angina, NSTEMI, and STEMI. Successive universal definitions of myocardial infarction (Thygesen et al., 2018) and iterative society guidelines reflect the growing precision of biomarker assays and the consolidation of risk-stratification tools.
Related topics
Seminal works
- thygesen-2018
- byrne-2023
- gulati-2021
- fox-2006
Frequently asked questions
- Does chest pain always mean a heart attack?
- No. Acute chest pain has many cardiac and non-cardiac causes, and only a minority of emergency presentations are due to acute coronary syndrome; structured assessment with the electrocardiogram, troponin, and risk scores is used to estimate the probability of a cardiac cause.
- What is the difference between acute coronary syndrome and myocardial infarction?
- Acute coronary syndrome is the broader spectrum of acute myocardial ischaemia that includes unstable angina, NSTEMI, and STEMI; myocardial infarction refers specifically to the subset with detectable myocyte necrosis meeting the universal definition criteria.