ACS is an umbrella term that covers a spectrum of clinical presentations. The common pathology is a ruptured plaque within a coronary artery leading to thrombosis and flow limitation. The exact clinical picture depends upon the site of plaque rupture and the extent of flow limitation.
- Unstable Angina
This is a syndrome where a patient develops worsening of angina symptoms such that angina occurs on increasingly less exertion, or at rest. It can occur in patients with previously stable symptoms, or can be seen in patients without any previous problems. It is not associated with a rise in cardiac markers such as Troponin, but ECG changes such as ST segment depression or T-wave inversion can sometimes be seen. The culprit coronary artery in unstable angina is generally narrowed but not completely occluded giving symptoms of ischaemia without myocardial infarction. - Non ST Elevation Myocardial Infarction (NSTEMI)
Patients who have sustained a non- ST segment elevation myocardial infarction (NSTEMI) have generally had prolonged chest pain at rest. Sometimes pain can come on with exertion but not be relieved by rest or GTN spray. NSTEMI patients have a rise in cardiac markers such as Troponin, indicating that there has been myocardial damage. ECG changes can be quite variable in NSTEMI. By definition, ST segment elevation is not seen, but in some cases the ECG can be normal, and in other cases, either ST segment depression or T-wave inversion can be seen. The culprit coronary artery in NSTEMI may be an occluded small branch or a non occlusive thrombus may embolise causing occlusion of distal small vessels. - ST Elevation Myocardial Infarction (STEMI)
ST segment elevation myocardial infarction (STEMI) is characterised by ECG change. Again patients tend to present with prolonged chest pain at rest and cardiac markers such as Troponin are elevated. The important ECG change is elevation of the ST segment. This needs to be at least 1mm of ST elevation in two or more contiguous limb leads on the standard 12 lead ECG, or at least 2mm in 2 or more contiguous chest leads. More rarely, patients with STEMI can have new left bundle branch block (LBBB) on their ECG. As well as making the diagnosis of STEMI, the areas of ST elevation on the ECG can be used to identify which region of the heart is affected. The culprit artery in STEMI is generally occluded by thrombus and it is generally one of the main coronary arteries that is affected.
Page last reviewed: 05 Jun 2020
