Myocardial Infarction Type 1 Versus Type 2
Type 1 myocardial infarction (MI) is defined by acute atherothrombosis (plaque rupture, ulceration, erosion, or thrombosis) causing myocardial ischemia with a rise and/or fall in cardiac troponin. [1]
Type 2 MI is defined by oxygen supply–demand mismatch causing myocardial ischemia in the absence of acute atherothrombotic coronary events. [1]
Core Etiology
Type 1 MI (acute coronary atherothrombosis)
- MI is attributed to atherosclerotic plaque rupture with thrombosis. [2]
Type 2 MI (oxygen supply–demand mismatch)
- MI is attributed to an imbalance between myocardial oxygen supply and demand unrelated to acute plaque disruption and thrombosis. [2]
Diagnostic Framework
Both type 1 and type 2 MI require:
- A rise and/or fall in cardiac troponin with at least one value above the 99th percentile of the upper reference limit. [3]
- Evidence of myocardial ischemia (e.g., ischemic symptoms, ischemic ECG changes, imaging evidence of new regional wall-motion abnormality, or identification of a coronary thrombus when applicable). [3]
The differentiator is the mechanism:
- Type 1 requires acute atherothrombosis. [2]
- Type 2 requires ischemia due to supply–demand imbalance without acute atherothrombotic coronary mechanisms. [1]
Typical Clinical Contexts
Type 1 MI
- Often presents with the classic acute coronary syndrome pathway driven by plaque disruption and thrombosis. [3]
Type 2 MI
- Often occurs during another acute illness or physiologic stress that drives oxygen supply–demand mismatch. [1]
Mechanisms and Precipitating Conditions (Type 2 MI)
Common oxygen supply–demand imbalance settings used in Universal Definition classification include:
- Sustained tachyarrhythmia. [4]
- Severe bradyarrhythmia. [4]
- Severe hypertension. [4]
- Respiratory failure. [4]
- Shock. [4]
- Severe anemia. [4]
- Hypotension. [4]
Prognosis Differences
Type 2 MI generally carries higher 1-year all-cause mortality than type 1 MI in large adjudicated cohorts.
- In a JAMA Network Open secondary analysis of adjudicated type 1 vs type 2 MI, 1-year all-cause mortality was 15% for type 1 MI versus 23% for type 2 MI. [5]
- Mortality risk varied by the underlying precipitating imbalance in type 2 MI (e.g., higher mortality associated with hypoxemia or anemia in that analysis). [5]
Key Differentiation Pitfalls
- Troponin elevation alone does not establish MI type 1 or type 2. The diagnosis requires a troponin rise/fall plus clinical, ECG, or imaging evidence of ischemia. [3]
- Type 2 MI should not be assigned when acute coronary atherothrombosis is identified as the mechanism. [2]
- Type 2 MI should not be treated as equivalent to type 1 MI because the underlying driver is different (oxygen mismatch rather than plaque thrombosis). [1]