ST-elevation myocardial infarction

ST-elevation myocardial infarction (STEMI) presents with central chest pain that is classically heavy in nature, like a sensation of pressure or squeezing. Examination is variable, and findings range from normal to a critically unwell patient in cardiogenic shock.

Make a clinical working diagnosis of STEMI and start immediate treatment when a patient presents with symptoms suggestive of myocardial ischaemia and has persistent ST-segment elevation in at least 2 anatomically contiguous ECG leads.

Give a loading dose of aspirin as soon as possible to any patient with suspected acute coronary syndrome.

A rise in cardiac-specific troponins confirms the diagnosis but do not wait for laboratory results before starting treatment.

Immediate and prompt reperfusion can prevent or minimise myocardial damage and improve the chances of survival and recovery. Primary percutaneous coronary intervention (PCI) is the best management option for most patients, with fibrinolysis reserved for those without access to timely primary PCI.

Survivors of acute MI should receive cardiac rehabilitation and be closely followed up to ensure adequate modification of risk factors and optimisation of (and adherence to) pharmacotherapy for secondary prevention, and to monitor for the development of post MI complications and/or residual angina symptoms.

Acute myocardial infarction is myocardial cell death that occurs because of a prolonged mismatch between perfusion and demand. In the case of ST-elevation myocardial infarction (STEMI) this is caused predominantly by complete atherothrombotic occlusion of a coronary artery.

In the appropriate clinical context, a STEMI is diagnosed clinically when there is new (or increased) and persistent ST-segment elevation in at least two contiguous leads of ≥1 mm in all leads other than leads V2-V3 where the following cut-off points apply:[1]Thygesen K, Alpert JS, Jaffe AS, et al. Fourth universal definition of myocardial infarction (2018). Glob Heart. 2018 Dec;13(4):305-38. https://www.sciencedirect.com/science/article/pii/S2211816018301388?via%3Dihub http://www.ncbi.nlm.nih.gov/pubmed/30154043?tool=bestpractice.com  

• ≥2.5 mm in men <40 years old

• ≥2 mm in men >40 years old

• ≥1.5 mm in women regardless of age

  • 1 mm = 1 small square (at a standard ECG calibration of 10 mm/mV).

Contiguous ECG leads lie next to each other anatomically and indicate a specific myocardial territory.