Unstable angina is a type of angina pectoris that is irregular. It is a type of acute coronary syndrome

Acute coronary syndrome

Acute coronary syndrome is usually one of three diseases involving the coronary arteries: ST elevation myocardial infarction , non ST elevation myocardial infarction , or unstable angina ....

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It can be difficult to distinguish from non–Q-wave myocardial infarction

Myocardial infarction

Myocardial infarction or acute myocardial infarction , commonly known as a heart attack, results from the interruption of blood supply to a part of the heart, causing heart cells to die...

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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: (1) occurs at rest or minimal exertion and usually lasts >20 minutes (if nitroglycerin is not administered); (2) being severe and described as frank pain, and of new onset (i.e., within 1 month); (3) occurs with a crescendo pattern (more severe, prolonged, or increased frequency than previously). 50% 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 NSTEMI.