Definition
- Non-ST-elevation acute coronary syndrome (NSTE-ACS): an acute coronary syndrome (ACS) without persistent ST elevation on the electrocardiogram (ECG). It includes two conditions, told apart by troponin (European Society of Cardiology, ESC 2023 ACS guideline):
- Non-ST-elevation myocardial infarction (NSTEMI): acute ischaemia with a rise and/or fall of cardiac troponin above the 99th percentile (a myocardial infarction (MI) by the Fourth Universal Definition, topic 26); necrosis is usually subendocardial.
- Unstable angina (UA): ischaemia at rest or on minimal effort without myocyte necrosis (troponin not raised). With high-sensitivity troponin assays it has become less common and carries a lower risk.
Image: “ACS scheme” by User:Stevenfruitsmaak, CC BY-SA 3.0, via Wikimedia Commons.
- Clinical forms of UA: rest angina (usually over 20 minutes); new-onset angina of Canadian Cardiovascular Society (CCS) class II–III; crescendo angina (previously stable angina becoming more frequent, longer or provoked by less effort, by at least one CCS class to class III); post-infarction angina.
- NSTE-ACS is more frequent than ST-elevation MI (STEMI); patients are older with more comorbidity (diabetes, chronic kidney disease (CKD), previous MI).