Non-ST elevation coronary syndrome
Non-ST elevation coronary syndrome (NSTE-ACS) is an umbrella term for non-ST elevation myocardial infarction (NSTEMI) and unstable angina. They're two forms of acute coronary syndrome characterised by the lack of ST elevations.
An non-ST elevation myocardial infarction (NSTEMI) is a clinical form of acute myocardial infarction and one form of acute coronary syndrome. It is defined as the presence of ischaemic symptoms, lack of ST-elevations in a pattern consistent with the blood supply of one coronary artery and a rise and/or fall in troponin levels. Ischaemic symptoms are classically angina, but may also be dyspnoea, nausea, sweating, anxiety, or non-anginal chest pain. For initial evaluation, see acute coronary syndrome.
Unstable angina is defined as the presence of ischaemic symptoms in rest without an elevation of troponin levels beyond the upper normal level. If the occlusion is severe enough to cause ischaemia (and resulting symptoms) but not severe enough to cause infarction, the result is unstable angina.
ECG changes
While ST-elevations are never present in NSTE-ACS (in which case it would be a STEMI), other ECG changes may be present, like ST-depression or T wave inversion. In unstable angina, these changes are transient. ECG changes are a negative prognostic sign.
It's important to know that unlike ST elevation, ST depression cannot localise the lesion. This means that ST depression in for example "inferior leads" (II, III, aVF) does not indicate that the NSTEMI is localised to the inferior leads.
Initial management
The decision of whether to go for an invasive (PCI) or conservative (only drugs) management of NSTE-ACS depends on the patient’s risk stratification. This risk stratification should be done as early as possible. The higher the risk, the sooner they should undergo PCI. Generally, the urgency is evaluated like this:
- Very high risk/unstable patients – PCI within 2 hours
- Drug-refractory angina
- Haemodynamic instability
- Life-threatening arrhythmias
- Mechanical complications
- High risk patients – PCI within 24 hours
- Positive troponin dynamics
- ECG changes
- Low risk patients – Conservative approach initially, PCI electively
- Negative troponin dynamics
- Absence of angina
- Low GRACE-score
Much of the initial management of NSTE-ACS is the same as for STEMI:
- Aspirin (300 mg loading dose) – in all cases
- P2Y12 inhibitor loading dose (ticagrelor only) – in all cases
- Atorvastatin – in all cases
- Unfractionated heparin – in all cases where an invasive approach is taken except with pre-existing anticoagulation
- Metoprolol – in all cases except with heart failure
- Nitroglycerine – in case of chest pain
- Morphine – in case of chest pain not responsive to nitro
- Oxygen – in case of O2 sat < 90%