Subendocardial myocardial infarction

Non-ST elevation MI (previously termed non-Q wave MI, often referred to as non-STEMI), is an unstable coronary syndrome which is differentiated from unstable angina by a subsequent rise in cardiac enzymes. ECG findings often include ST depression but do not include new pathological Q waves.

The term acute coronary syndrome is characterized by a clinical syndrome of acute ischaemic chest pain with either rest pain or a crescendo pattern of pain on minimal exertion, associated with ECG changes of ischaemia (ST elevation or depression or T inversion)

• ST elevation myocardial infarction (STEMI) is then distinguished from other forms of acute coronary syndrome (ACS) by the presence of persistent ST elevation
  • distinction between non-STEMI and unstable angina is based on the presence (non-STEMI) or absence (unstable angina) of a rise in cardiac enzymes or troponin

NICE note that people with non-ST segment elevation acute coronary syndrome (NSTEMI) (ACS) have a high incidence of recurrent myocardial ischaemia, a similar long-term outcome to those with ST elevation myocardial infarction (STEMI), and a worse outcome than for people with unstable angina (1).

Click here for ECG examples of non-ST elevation MI

Reference:

1. National Institute for Health and Care Excellence. Acute coronary syndromes. Nov 2020 [internet publication]