Overview of acute coronary syndrome

Last reviewed: 23 Aug 2023
Last updated: 25 Oct 2022

This page compiles our content related to acute coronary syndrome. For further information on diagnosis and treatment, follow the links below to our full BMJ Best Practice topics on the relevant conditions and symptoms.



Unstable angina (UA) is an acute coronary syndrome that is defined by the absence of biochemical evidence of myocardial damage.[4] UA is characterized by specific clinical findings of prolonged (>20 minutes) angina at rest; new onset of severe angina; angina that is increasing in frequency, longer in duration, or lower in threshold; or angina that occurs after a recent episode of myocardial infarction.[4] The ECG may be normal or may show ST-segment depression, transient ST-segment elevation, or T-wave inversion.[4] Cardiac biomarkers (high-sensitivity cardiac troponins) should be measured on presentation to rule out acute myocardial infarction; subsequent/serial measurements may be needed.[4][5] The early management of patients with suspected UA is focused on initial interventions and triage according to the presumptive diagnosis.

Non-ST-elevation myocardial infarction (NSTEMI) is an acute ischemic event causing myocyte necrosis. The initial ECG may show ischemic changes such as ST depression, T-wave changes, or transient ST elevation; however, ECG may also be normal or show non-specific changes. The distinction from unstable angina (UA) is based on cardiac biomarkers; high-sensitivity cardiac troponins are elevated (>99th percentile of normal) at presentation or after several hours in NSTEMI.[3] Treatment is directed toward relief of ischemia, prevention of further thrombosis or embolism, and stabilization of hemodynamic status, followed by early risk stratification for further treatment.

ST-elevation myocardial infarction (STEMI) is suspected when a patient presents with persistent ST-segment elevation in two or more anatomically contiguous ECG leads in the context of a consistent clinical history.[1] Cardiac biomarkers (troponins) are elevated. Treatment should, however, be started immediately in patients with a typical history and ECG changes, without waiting for laboratory results. Immediate and prompt reperfusion can prevent or minimize myocardial damage and improve the chances of survival and recovery.[6]



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