Unstable angina

Unstable angina (UA) is a type of angina pectoris that is irregular. It is also classified as a type of acute coronary syndrome (ACS).

It can be difficult to distinguish unstable angina from non–Q-wave myocardial infarction. Unstable angina (UA) and non-ST elevation (non-Q wave) myocardial infarction (NSTEMI) differ primarily in whether the ischemia is severe enough to cause sufficient myocardial damage to release detectable quantities of a marker of myocardial injury. Unstable angina is considered to be present in patients with ischemic symptoms suggestive of an ACS and no elevation in troponin, with or without ECG changes indicative of ischemia (e.g., ST segment depression or transient elevation or new T wave inversion). Since an elevation in troponin may not be detectable for up to 12 hours after presentation, UA and NSTEMI are frequently indistinguishable at initial evaluation.

Pathophysiology

Unstable angina is angina pectoris caused by disruption of an atherosclerotic plaque with partial thrombosis and possibly embolization or vasospasm.