Overview of acute coronary syndrome

Last reviewed: 27 Oct 2022
Last updated: 25 Oct 2022



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]



Editorial Team

BMJ Publishing Group


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