Non-ST Segment Elevation Myocardial Infarction - NSTEMI

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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.

The three types of ACS are:

  • unstable angina
  • NSTEMI
  • STEMI (ST Segment Elevation Myocardial Infarction) - otherwise known as a “full” heart attack

All three types of ACS are produced when a plaque ruptures in a coronary artery.

The ruptured plaque and the associated blood clot produce partial or complete blockage of the artery, and the heart muscle supplied by that artery is either dying or is in grave danger of sustaining irreversible damage.

If the blockage is complete, a STEMI occurs. In a STEMI, the ST segments on the electrocardiogram become elevated (hence, the name), and cardiac enzymes greatly increase. These findings indicate that significant heart cell death is occurring.

With unstable angina and NSTEMI, the blockage is not (yet) complete. Clinically, NSTEMI is identical to unstable angina except for one thing. In NSTEMI, in contrast to unstable angina, the 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. In other words, the imminent risk of a "full" myocardial infarction (that is, a STEMI), with irreversible death of part of the heart muscle, is very high in both NSTEMI and unstable angina.

Diagnosing NSTEMI

The diagnosis of NSTEMI is made when a patient has symptoms of unstable angina, has no ST-segment elevation on the ECG, and has an elevation in cardiac enzymes. (Unstable angina is present if angina occurs at rest; if new onset angina begins that significantly limits physical activity; or if previously stable angina becomes more frequent or occurs with notably less exertion than before.)

Treating NSTEMI

The treatment of NSTEMI is identical to the treatment of unstable angina.

Fundamentally, the first step in treating NSTEMI is to stabilize the heart muscle to prevent further damage. This can usually be accomplished by administering oxygen, morphine, beta blockers, aspirin, Plavix, and a statin drug.

Once a patient with NSTEMI is stabilized, the cardiologist will need to decide whether to continue with “conservative” therapy (that is, drug therapy alone) or instead whether to use more “aggressive” treatment - angioplasty and stenting.

This decision generally is made by assessing several risk factors that help to predict whether the stabilized patient is likely to remain stable on drug therapy alone. These risk factors include age; the presence of hypertension, diabetes, high lipid levels, smoking history, or a strong family history of early heart disease; a prior history of a blocked coronary artery; and the level of elevation in cardiac enzymes. If more than two of these risk factors are present, the aggressive approach to therapy is likely to result in a better outcome.

Sources:

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.

Amsterdam EA, Wenger NK, Brindis RG, et al. 2014 AHA/ACC guideline for the management of patients with non-ST-elevation acute coronary syndromes: executive summary: a report of the American College of Cardiology/American Heart Association Task Force on Practice Guidelines. Circulation 2014; 130:2354.

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