Fourth Universal Definition of Myocardial Infarction

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The fourth universal definition focuses on identification of myocardial injury–elevated troponin–and the process of determining the mechanism as ischemic (infarction) or non-ischemic.

An acute myocardial infarction (AMI) is defined as acute myocardial injury with:
• Troponin rise and fall, or fall of already elevated troponin value (with one value above the 99th percentile URL) and
• At least one of the following:

• Symptoms of myocardial ischemia;
• ECG – New ischemic changes;
• ECG – Development of pathologic Q waves;
• Imaging evidence of new loss of viable myocardium or new regional wall motion abnormality in a pattern consistent with an ischemic etiology;
• Identification of a coronary thrombus by angiography or autopsy (not for types 2 or 3 MIs).

Type 1 MI A coronary artery event via plaque disruption or dissection


Type 2 MI Not a coronary artery event. Myocardial oxygen demand is not met by oxygen supply. Coronary artery plaque may or may not be present but is unchanged.


Demand Ischemia Cardiac demand ischemia is the same thing as angina, supply-demand mismatch without infarction:

•       Angina + elevated troponin = AMI

•       Demand ischemia + elevated troponin = type 2 AMI


Acute myocardial injury is defined as ≥ 20% variance in troponin values (to distinguish from stable elevation).

Coding Rules allow qualifying a diagnosis as “likely,” “probable,” “suspected” at the time of discharge (i.e., discharge summary).

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