ICD-10 Code I21.A1 – Myocardial infarction type 2 (2026): Diagnosis, Symptoms & Billing Guide
2026 ICD-10-CM Diagnosis Code I21.A1 – Myocardial infarction type 2
What it is
I21.A1 identifies a type 2 myocardial infarction, meaning heart muscle injury caused by an imbalance between oxygen supply and demand rather than a primary coronary artery blockage.
Clinical signs
Clinical features may include chest discomfort, shortness of breath, ischemic ECG changes, or elevated cardiac troponin with a clear supply-demand trigger. Clinical features vary; refer to documentation.
When to use this code
Use this code when the provider documents type 2 myocardial infarction and the record supports a secondary cause such as severe anemia, tachyarrhythmia, hypotension, or respiratory failure. You should code the documented MI type, not a generic acute MI, when the distinction is stated. Check documentation if the cause is unclear.
Do not use for
Do not use I21.A1 for type 1 myocardial infarction, old myocardial infarction, or isolated troponin elevation without a documented infarction. Avoid it when the record only describes demand ischemia or myocardial injury. Check documentation.
Coding tip
Confirm that the provider explicitly links the infarction to a supply-demand imbalance before assigning I21.A1.