I21
Acute myocardial infarction
Choose the additional character
I21 needs more characters to be billable. Pick the specific code below.
- I21.0ST elevation (STEMI) myocardial infarction of anterior wallMore levels
- I21.1ST elevation (STEMI) myocardial infarction of inferior wallMore levels
- I21.2ST elevation (STEMI) myocardial infarction of other sitesMore levels
- I21.3ST elevation (STEMI) myocardial infarction of unspecified siteBillable
- I21.4Non-ST elevation (NSTEMI) myocardial infarctionBillable
- I21.9Acute myocardial infarction, unspecifiedBillable
- I21.AOther type of myocardial infarctionMore levels
- I21.BMyocardial infarction with coronary microvascular dysfunctionBillable
This code does not map to a risk-adjusting HCC in the loaded models.
Coding notes
Excludes 1 never coded together · Excludes 2 may co-exist
cardiac infarction coronary (artery) embolism coronary (artery) occlusion coronary (artery) rupture coronary (artery) thrombosis infarction of heart, myocardium, or ventricle myocardial infarction specified as acute or with a stated duration of 4 weeks (28 days) or less from onset
old myocardial infarction (I25.2) postmyocardial infarction syndrome (I24.1) subsequent type 1 myocardial infarction (I22.-)
code, if applicable, to identify: exposure to environmental tobacco smoke (Z77.22) history of tobacco dependence (Z87.891) occupational exposure to environmental tobacco smoke (Z57.31) status post administration of tPA (rtPA) in a different facility within the last 24 hours prior to admission to current facility (Z92.82) tobacco dependence (F17.-) tobacco use (Z72.0)
the presence of hypertension (I10-I1A)
certain conditions originating in the perinatal period (P04-P96) certain infectious and parasitic diseases (A00-B99) complications of pregnancy, childbirth and the puerperium (O00-O9A) congenital malformations, deformations, and chromosomal abnormalities (Q00-Q99) endocrine, nutritional and metabolic diseases (E00-E88) injury, poisoning and certain other consequences of external causes (S00-T88) neoplasms (C00-D49) symptoms, signs and abnormal clinical and laboratory findings, not elsewhere classified (R00-R94) systemic connective tissue disorders (M30-M36) transient cerebral ischemic attacks and related syndromes (G45.-)
Official Guidelines for I21
FY 2026 ›Sections that reference I21
- I.C.9.e.1)Type 1 ST elevation myocardial infarction (STEMI) and non-
… infarction meets the definition for “other diagnoses” (see Section III, Reporting Additional Diagnoses), codes from category I21 may continue to be reported. …
- I.C.9.e.4)Subsequent acute myocardial infarction
… the 4 week time frame of the initial AMI. A code from category I22 must be used in conjunction with a code from category I21. The sequencing of the I22 and I21 codes depends on the circumstances of the encounter. …
- I.C.9.e.2)Acute myocardial infarction, unspecified
Code I21.9, Acute myocardial infarction, unspecified, is the default for unspecified acute myocardial infarction or unspecified type. …
- I.C.9.e.5)Other Types of Myocardial Infarction
… 2 myocardial infarction (myocardial infarction due to demand ischemia or secondary to ischemic imbalance) is assigned to code I21.A1, Myocardial infarction type 2 with the underlying cause coded first, if applicable. …
- I.C.9.e.6)Myocardial Infarction with Coronary Microvascular Dysfunction
… Code I21.B, Myocardial infarction with coronary microvascular dysfunction, is assigned for myocardial infarction with coronary …
Sections whose FY 2026 text names I21, its I21 category, or a range containing it — the chapter guidance above is the authoritative source.