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Non-ST Segment Elevation Myocardial Infarction - NSTEMI


Updated May 16, 2014

Written or reviewed by a board-certified physician. See About.com's Medical Review Board.

Non-ST Segment Elevation Myocardial Infarction (NSTEMI) is one of the three types of Acute Coronary Syndrome (ACS), and like all ACS, NSTEMI should be considered a medical emergency.

NSTEMI is identical to unstable angina except for one thing. In NSTEMI, in contrast to unstable angina, cardiac enzyme blood tests are abnormal, indicating that at least some actual cell damage is occurring to heart muscle cells.

Fundamentally, however, in every other way NSTEMI and unstable angina are identical. They both indicate that a plaque has ruptured in a coronary artery, that the ruptured plaque and the associated blood clot are producing partial blockage of the artery, and that the heart muscle supplied by that artery is in grave danger of sustaining irreversible damage. In other words, the imminent risk of a "full" myocardial infarction, with irreversible death of part of the heart muscle, is very high in both NSTEMI and unstable angina.

The symptoms, the clinical circumstances, and the treatment of NSTEMI are identical to those of unstable angina.You can read about those aspects of NSTEMI here.


Thygesen, K, Alpert, JS, White, HD, et al. Universal definition of myocardial infarction: Kristian Thygesen, Joseph S. Alpert and Harvey D. White on behalf of the Joint ESC/ACCF/AHA/WHF Task Force for the Redefinition of Myocardial Infarction. Eur Heart J 2007; 28:2525.

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