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.
Acute coronary syndrome (ACS) refers to a spectrum of acute myocardial ischaemia and/or infarction. Classically ACS has been divided into three clinical categories according to the presence or absence of ST-segment elevation on the initial ECG, together with measurement of myocardial biomarkers, such as high-sensitivity cardiac troponins. In ST-elevation myocardial infarction (STEMI) the ECG shows persistent ST-segment elevation in two or more anatomically contiguous leads. Unstable angina and non-ST-elevation myocardial infarction (NSTEMI) represent a continuum of pathology, differing mainly by the presence of markers of myocardial damage in NSTEMI. Therefore some guidelines have grouped unstable angina and NSTEMI as 'non-ST-elevation acute coronary syndromes'.
Unstable angina (UA) is an acute coronary syndrome that is defined by the absence of biochemical evidence of myocardial damage. UA is characterised 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. The ECG may be normal or may show ST-segment depression, transient ST-segment elevation, or T-wave inversion. Cardiac biomarkers (high-sensitivity cardiac troponins) should be measured on presentation to rule out acute myocardial infarction; subsequent/serial measurements may be needed. 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 ischaemic event causing myocyte necrosis. The initial ECG may show ischaemic 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. Treatment is directed towards relief of ischaemia, prevention of further thrombosis or embolism, and stabilisation of haemodynamic 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. 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 minimise myocardial damage and improve the chances of survival and recovery.
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This overview has been compiled using the information in existing sub-topics.
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