Unstable angina is an acute coronary syndrome characterized by an unstable coronary plaque causing symptoms of myocardial ischemia in one of three patterns:

1. Exertional angina of new onset. Even if relieved with rest and requiring a consistent amount of exertion to procedure symptoms, when angina first occurs it is considered unstable.

2. Exertional angina that was previously stable and now occurs with less physical exertion.

3. Anginal symptoms at rest without physical exertion.