ICD-10 Code I21.A – Other type of myocardial infarction (2026): Diagnosis, Symptoms & Billing Guide
2026 ICD-10-CM Diagnosis Code I21.A – Other type of myocardial infarction
What it is
I21.A identifies a myocardial infarction that does not fit the standard STEMI or NSTEMI categories. Use it for documented “other” infarction types when the record specifies an atypical or nonstandard MI classification.
Clinical signs
Clinical features vary; refer to documentation. You may see chest pain, ischemic ECG changes, elevated cardiac biomarkers, or imaging evidence of infarction, but the key point is the provider’s specific diagnosis of another MI type.
When to use this code
Use I21.A when the clinician documents an acute myocardial infarction as “other type,” and the record does not support a more specific I21 category. It is appropriate when the type is clearly stated but does not match the usual subtypes. Check documentation for the exact wording and episode timing.
Do not use for
Do not use this code for old or healed infarction, suspected MI without confirmation, or a clearly classified STEMI or NSTEMI. If the note names a different acute MI subtype, code that specific category instead.
Coding tip
Code I21.A only when the provider explicitly documents an “other” myocardial infarction; otherwise, query for clarification.