SOLACI | Latin American Society of Interventional Cardiology

The Fourth Universal Definition of Myocardial Infarction is a document developed jointly by the European Society of Cardiology (ESC), the American College of Cardiology (ACC), the American Heart Association (AHA), and the World Heart Federation (WHF).

The Fourth Definition was necessary for multiple reasons, including increasingly higher troponin sensitivity.

While troponin obviously does not modify the clinical criteria for infarction, this increased sensitivity has unmasked many circumstances or clinical contexts where myocardial injury can exist even unrelated to an acute coronary syndrome.

This is the essence of the Fourth Definition, summarized in these ten commandments:

Myocardial injury is defined as any instance of troponin elevation above the 99th percentile of the upper reference limit.
Myocardial injury may be acute (rise and/or fall of troponin values), as in acute heart failure, or chronic (≤20% variation) as in patients with chronic kidney disease.
Myocardial injury may occur in a variety of situations, such as cardiac procedural interventions with or without cardiovascular illness.
The occurrence of acute myocardial injury in a setting of acute myocardial ischemia defines an acute myocardial infarction.
An infarction type 1 is an acute myocardial injury related to acute atherothrombotic coronary artery disease, generated by plaque disruption reducing the blood supply to the myocardium.
A myocardial infarction type 2 is an acute myocardial injury related to an imbalance between the oxygen supply and an increased demand secondary to stressors unrelated to acute coronary disease.
A myocardial infarction type 3 is found in patients who suffer cardiac sudden death, with symptoms suggestive of myocardial ischemia and electrocardiographic changes. However, biomarker values cannot be obtained in these cases.
A myocardial infarction type 4a is related to an angioplasty; troponin values increase 5 times above the 99th percentile of the upper reference limit after the procedure from normal values at baseline or, if elevated, stable baseline values. This diagnosis requires electrocardiographic or imaging evidence of new myocardial ischemia, or obvious complications during the procedure leading to reduced coronary blood flow for a given time.
A myocardial infarction type 4b is an acute myocardial injury related to stent thrombosis, and type 4c is associated with restenosis.
A myocardial infarction type 5 is an increase in troponin values >10 times the 99th percentile of the upper reference limit related to myocardial revascularization surgery. New myocardial ischemia or new loss of viability is required.