Patients with unstable angina or non-ST elevation myocardial infarction can be at high risk of death or nonfatal myocardial infarction within hours or days of onset of the symptoms.
Patients who have one or more of the following characteristics are at high risk:*
A history of increasing frequency of ischemic symptoms (e.g. chest discomfort, dyspnea) over the preceding 48 hours
Chest discomfort that is ongoing and prolonged (lasting more than 20 minutes) at rest
Pulmonary edema most likely due to ischemia
A new or worsening mitral regurgitation murmur
An S3 gallop
New or worsening rales
Hypotension, bradycardia, tachycardia
Age greater than 75 years
Angina at rest with transient ST segment changes greater than 0.5 mm
A new or presumed new bundle branch block
Sustained ventricular tachycardia
Elevated Troponin T, Troponin I, or CK-MB (e.g. Troponin T or Troponin I greater than 0.1 ng per ml
*From the chart representing short term risk of death or nonfatal MI available in the 2011 AHA Unstable Angina/non-ST elevation myocardial infarction updated guidelines (Table 7, p e442) available at: http://circ.ahajournals.org/content/123/18/e426.full.pdf.