Unstable angina and non-ST-elevation myocardial infarction

What it is

Acute coronary syndrome is the clinical manifestation of myocardial infarct, and commonly the default working diagnosis in a patient with new onset chest pain suspected to be of cardiac ischemic origin. New onset chest pain is MI until proven otherwise. Ischemic heart disease is either clinically silent, that is asymptomatic, or symptomatic. Stable angina, with symptoms with exertion, is symptomatic ischemic heart disease and is not one of the acute coronary syndromes. The acute coronary syndromes are three: unstable angina, non ST-segment elevation MI, and ST-segment elevation MI. Two of the three have no ST elevation, and only the biomarkers tell them apart:

• Stable angina, which is not one of the acute coronary syndromes: no ST elevation, biomarkers negative, symptoms at exertion, under 15 min
• Unstable angina: no ST elevation, biomarkers negative, symptoms at rest
• NSTEMI: no ST elevation, biomarkers positive
• STEMI: ST elevation, biomarkers positive

At the time of presentation, UA and NSTEMI may be indistinguishable and can be identically managed. Cardiac troponins, where the elevated enzymes show evidence of infarction, are what distinguish the one from the other.