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).
Download the complete tip, Fourth Universal Definition of Myocardial Infarction.