The following are key points to remember from this Expert Consensus Document on the Fourth Universal Definition of Myocardial Infarction (MI):

1. The current (fourth) Universal Definition of MI Expert Consensus Document updates the definition of MI to accommodate the increased use of high-sensitivity cardiac troponin (hs-cTn).
2. Detection of an elevated cTn value above the 99th percentile upper reference limit (URL) is defined as myocardial injury. The injury is considered acute if there is a rise and/or fall of cTn values.
3. The criteria for type 1 MI includes detection of a rise and/or fall of cTn with at least one value above the 99th percentile and with at least one of the following:
1. Symptoms of acute myocardial ischemia;
2. New ischemic electrocardiographic (ECG) changes;
3. Development of pathological Q waves;
4. Imaging evidence of new loss of viable myocardium or new regional wall motion abnormality in a pattern consistent with an ischemic etiology;
5. Identification of a coronary thrombus by angiography including intracoronary imaging or by autopsy.
4. The criteria for type 2 MI includes detection of a rise and/or fall of cTn with at least one value above the 99th percentile and evidence of an imbalance between myocardial oxygen supply and demand unrelated to coronary thrombosis, requiring at least one of the following:
1. Symptoms of acute myocardial ischemia;
2. New ischemic ECG changes;
3. Development of pathological Q waves;
4. Imaging evidence of new loss of viable myocardium, or new regional wall motion abnormality in a pattern consistent with an ischemic etiology.
5. Cardiac procedural myocardial injury is arbitrarily defined by increases of cTn values (>99th percentile URL) in patients with normal baseline values (≤99th percentile URL) or a rise of cTn values >20% of the baseline value when it is above the 99th percentile, but it is stable or falling.
6. Coronary intervention-related MI is arbitrarily defined by elevation of cTn values >5 times the 99th percentile URL in patients with normal baseline values. In patients with elevated pre-procedure cTn in whom the cTn levels are stable (≤20% variation) or falling, the post-procedure cTn must rise by >20%. However, the absolute post-procedural value must still be at least five times the 99th percentile URL. In addition, one of the following elements is required:
1. New ischemic ECG changes;
2. Development of new pathological Q waves;
3. Angiographic findings consistent with a procedural flow-limiting complication such as coronary dissection, occlusion of a major epicardial artery or a side branch occlusion/thrombus, disruption of collateral flow or distal embolization.
7. Coronary artery bypass grafting (CABG)-related MI is arbitrarily defined as elevation of cTn values >10 times the 99th percentile URL in patients with normal baseline cTn values. In patients with elevated pre-procedure cTn in whom cTn levels are stable (≤20% variation) or falling, the post-procedure cTn must rise by >20%. However, the absolute post-procedural value still must be >10 times the 99th percentile URL. In addition, one of the following elements is required:
1. Development of new pathological Q waves;
2. Angiographic documented new graft occlusion or new native coronary artery occlusion;
3. Imaging evidence of new loss of viable myocardium or new regional wall motion abnormality in a pattern consistent with an ischemic etiology.
8. It is increasingly recognized that there is a group of MI patients with no angiographic obstructive coronary artery disease (≥50% diameter stenosis in a major epicardial vessel), and the term “myocardial infarction with non-obstructive coronary arteries (MINOCA)” has been coined for this entity.
9. Patients may have elevated cTn values and marked decreases in ejection fraction due to sepsis caused by endotoxin, with myocardial function recovering completely with normal ejection fraction once the sepsis is treated.
10. Arriving at a diagnosis of MI using the criteria set forth in this document requires integration of clinical findings, patterns on the ECG, laboratory data, observations from imaging procedures, and on occasion pathological findings, all viewed in the context of the time horizon over which the suspected event unfolds.

Clinical Topics: Acute Coronary Syndromes, Arrhythmias and Clinical EP, Cardiac Surgery, Cardiovascular Care Team, Invasive Cardiovascular Angiography and Intervention, Noninvasive Imaging, Stable Ischemic Heart Disease, Atherosclerotic Disease (CAD/PAD), ACS and Cardiac Biomarkers, SCD/Ventricular Arrhythmias, Aortic Surgery, Cardiac Surgery and Arrhythmias, Cardiac Surgery and SIHD, Interventions and ACS, Interventions and Coronary Artery Disease, Interventions and Imaging, Angiography, Nuclear Imaging, Chronic Angina

Keywords: ESC Congress, ESC18, Acute Coronary Syndrome, Angiography, Atherosclerosis, Biomarkers, Cardiac Catheterization, Cardiac Surgical Procedures, Consensus, Coronary Artery Bypass, Coronary Artery Disease, Coronary Occlusion, Coronary Restenosis, Coronary Thrombosis, Death, Sudden, Cardiac, Diabetes Mellitus, Type 2, Diagnostic Imaging, Electrocardiography, Endotoxins, Myocardial Infarction, Myocardial Ischemia, Myocardium, Percutaneous Coronary Intervention, Perioperative Period, Sepsis, Stents, Stroke Volume, Thrombosis, Troponin

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