Clinical classification of acute myocardial infarction
| Myocardial infarction | |
 | |
|---|---|
| Acute Myocardial infarction; Posterior wall. Image courtesy of Professor Peter Anderson DVM PhD and published with permission © PEIR, University of Alabama at Birmingham, Department of Pathology | |
| ICD-10 | I21-I22 |
| ICD-9 | 410 |
| DiseasesDB | 8664 |
| MedlinePlus | 000195 |
| eMedicine | med/1567 emerg/327 ped/2520 |
| Cardiology Network |
 Discuss Clinical classification of acute myocardial infarction further in the WikiDoc Cardiology Network |
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]
Associate Editor-In-Chief: Cafer Zorkun, M.D., Ph.D. [2]
Prior MI Classification Schemes
There have been several prior classification schemes for characterizing MI:
1. Transmural (necrosis of full thickness of ventricle) vs. non transmural (necrosis of partial thickness of ventricle)
2. Q wave vs. non Q wave: Based upon the development of electrocardiographic Q waves representing electrically inert tissue.
3. ST elevation MI (STEMI) and Non ST elevation myocardial infarction (NSTEMI)
At one time it was thought that Transmural MI and Q wave MI were synonymous. However, not all Q wave MIs are transmural, and not all transmural MIs are associated with Q waves.
Likewise, not all ST elevation MIs go on to cause q waves. Non ST elevation MIs can result in q waves.
Thus, ST elevation MI should not be equated with transmural MI or q wave MI. Likewise, Non ST elevation MI should not be equated with non transmural MI or non q wave MI. These 3 designations reflect three separate but overlapping characterization schemes.
New MI Clinical Classification System
A new clinical evidence based classification system has been introduced by Thygesen K, Alpert JS, White HD, et al. and jointly sponsored by the American College of Cardiology (ACC), American Heart Association (AHA), European Society of Cardiology (ESC), and the World Heart Federation (WHF).[1]
Criteria for Diagnosis of Acute Myocardial Infarction
"The term myocardial infarction should be used when there is evidence of myocardial necrosis in a clinical setting consistent with myocardial ischemia. Under these conditions any one of the following criteria meets the diagnosis for acute myocardial infarction". [1]
Below are the criteria quoted from the Thygesen article:
- Detection of rise and/or fall of cardiac biomarkers (preferably Troponin) with at least one of the following
- Sudden unexpected cardiac death, including cardiac arrest, often with symptoms suggestive of myocardial ischemia, accompanied by presumably new ST segment elevation, or new LBBB, and/or evidence of fresh thrombus in a coronary artery by angiography and/or at autopsy, if death has occurred before blood samples could be obtained, or at a time before the appearance of cardiac biomarkers in the blood
- In patients with normal baseline troponin values, a greater than 3 times increase above the 99th percentile of the upper limit of normal of cardiac biomarkers has been designated as the definition of PCI related myocardial infarction. A subtype related to documented stent thrombosis is recognized.
- For patients with CABG surgery; (In patients with normal baseline troponin values) increases of cardiac biomarkers greater than 5 times, (> 5 times the 99th percentile upper limit of normal) and either new pathological Q waves or new LBBB or angiographically evidence of new graft or native vessel occlusion have been designated as defining CABG surgery related myocardial infarction.
- Pathological findings of acute myocardial infarction.
Criteria for Prior Myocardial Infarction
If any of the following are present, then a diagnosis of prior myocardial infarction is established:[1]
- Development of new pathological Q waves with or without symptoms
- Imaging evidence of a region of loss of viable myocardium that is thinned and fails to contract in the absence of a non ischemic cause.
- Pathological findings of healed or healing myocardial infarction.
Classification
Five types of MI are now recognized and classified as follows: [1]
Type 1: Spontaneous myocardial infarction related to ischemia due to a primary coronary event, such as plaque erosion and/or rupture, fissuring, or dissection.
Type 2: Myocardial infarction secondary to ischemia due to an imbalance of O2 supply and demand, as from coronary spasm or embolism, anemia, arrhythmias, hypertension, or hypotension
Type 3: Sudden unexpected cardiac death, including cardiac arrest, often with symptoms suggesting ischemia with new ST segment elevation; new left bundle branch block; or pathologic or angiographic evidence of fresh coronary thrombus (in the absence of reliable biomarker findings)
Type 4:
- a. Myocardial infarction associated with Percutaneous Coronary Interventions (PCI)
- b. Myocardial infarction associated with documented stent thrombosis.
Type 5: Myocardial infarction associated with Coronary Artery Bypass Graft surgery