Acute coronary syndromes refer to any constellation of clinical symptoms compatible with acute myocardial ischemia which may be life-threatening.
It encompasses unstable angina, non-ST-segment elevation myocardial infarction (NSTEMI) and ST-segment elevation myocardial infarction (STEMI).
Unstable angina is the ischemic discomfort that presents without persistent ST-segment elevation on ECG and without the presence of cardiac markers in the blood.
Non-ST-segment elevation myocardial infarction is diagnosed if cardiac markers are positive with ST-segment depression or with nonspecific or normal ECGs.
The patient typically presents with ischemic-type chest pain that is severe and prolonged and may occur at rest or may be caused by less exertion than previous episodes.