Definition
Unstable angina is angina pectoris caused by disruption of an atherosclerotic plaque with partial thrombosis and possibly embolization or vasospasm. It is characterized by at least one of the following:
- Occurs at rest or minimal exertion and usually lasts >20 minutes (if nitroglycerin is not administered)
- Being severe and described as frank pain, and of new onset (i.e., within 1 month)
- Occurs with a crescendo pattern (more severe, prolonged, or increased frequency than previously).
Fifty percent of people with unstable angina will have evidence of myocardial necrosis based on elevated cardiac serum markers such as creatine kinase isoenzyme (CK)-MB and troponin T or I, and thus have a diagnosis of non-ST elevation myocardial infarction.
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