I21.0 ICD-10-CM Code: ST elevation (STEMI) myocardial infarction of anterior wall
I21.0 is not a CMS-HCC payment code. MEAT criteria · RAF Calculator · free HCC coding tools
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FY 2026 Apr update / Diseases of the circulatory system (I00-I99) / Ischemic heart diseases (I20-I25)
I21.0
Header CodeICD-10-CMOfficial ICD-10-CMCodebook guidanceST elevation (STEMI) myocardial infarction of anterior wall
CMS-HCC V28
N/A—
Not mapped
CMS-HCC V24
N/A—
Not mapped
ACA/HHS
N/A—
Not mapped
ESRD/PACE
N/A—
Not mapped
RXHCC
N/A—
Not mapped
Code Book Path
Inclusion Terms
Official- Type 1 ST elevation myocardial infarction of anterior wall
Excludes 2
Official- certain conditions originating in the perinatal period (P04-P96)Inherited from I00-I99, I21
- certain infectious and parasitic diseases (A00-B99)Inherited from I00-I99, I21
- complications of pregnancy, childbirth and the puerperium (O00-O9A)Inherited from I00-I99, I21
- congenital malformations, deformations, and chromosomal abnormalities (Q00-Q99)Inherited from I00-I99, I21
- endocrine, nutritional and metabolic diseases (E00-E88)Inherited from I00-I99, I21
- injury, poisoning and certain other consequences of external causes (S00-T88)Inherited from I00-I99, I21
- neoplasms (C00-D49)Inherited from I00-I99, I21
- symptoms, signs and abnormal clinical and laboratory findings, not elsewhere classified (R00-R94)Inherited from I00-I99, I21
- systemic connective tissue disorders (M30-M36)Inherited from I00-I99, I21
- transient cerebral ischemic attacks and related syndromes (G45.-)Inherited from I00-I99, I21
- old myocardial infarction (I25.2)Inherited from I00-I99, I21
- postmyocardial infarction syndrome (I24.1)Inherited from I00-I99, I21
- subsequent type 1 myocardial infarction (I22.-)Inherited from I00-I99, I21
Related Codes
Includes
Official- cardiac infarctionInherited from I21
- coronary (artery) embolismInherited from I21
- coronary (artery) occlusionInherited from I21
- coronary (artery) ruptureInherited from I21
- coronary (artery) thrombosisInherited from I21
- infarction of heart, myocardium, or ventricleInherited from I21
- myocardial infarction specified as acute or with a stated duration of 4 weeks (28 days) or less from onsetInherited from I21
Excludes 1
OfficialNo Excludes 1 notes are included in this display for I21.0. Check the code and parent instructions in the Code Book.
Code First
OfficialNo Code First sequencing instructions are included in this display for I21.0. Check the code and parent instructions in the Code Book.
Use Additional
Official- code, if applicable, to identify:Inherited from I21
- exposure to environmental tobacco smoke (Z77.22)Inherited from I21
- history of tobacco dependence (Z87.891)Inherited from I21
- occupational exposure to environmental tobacco smoke (Z57.31)Inherited from I21
- status post administration of tPA (rtPA) in a different facility within the last 24 hours prior to admission to current facility (Z92.82)Inherited from I21
- tobacco dependence (F17.-)Inherited from I21
- tobacco use (Z72.0)Inherited from I21
Code Also
Official- the presence of hypertension (I10-I1A)Inherited from I20-I25
Current with CMS: FY2026 ICD-10-CM Apr 1 update (effective Apr 1 – Sep 30, 2026) · CMS-HCC V28, 100% phased in for payment year 2026. FY2027 code set already staged for October 1, 2026. How HCC Buddy stays current →
- Code
- I21.0
- Description
- ST elevation (STEMI) myocardial infarction of anterior wall
- HCC (V28)
- No CMS-HCC V28 mapping
- RAF reference coefficient
- —
- Billable
- No
- Payment year
- 2026
Coder workflow notes
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What This Code Means
I21.0 is the ICD-10-CM diagnosis code for st elevation (stemi) myocardial infarction of anterior wall. I21.0 sits in the ICD-10-CM chapter for diseases of the circulatory system (i00-i99), within the section covering ischemic heart diseases (i20-i25).
Header codes like I21.0 cannot be reported on claims directly; they organize child codes that share clinical context. Coders should select the billable child code that matches the documented presentation and then verify its current source-backed HCC mapping. Do not infer a child code or risk adjustment value from the header alone.
HCC Buddy maintains structured V28 and V24 mapping, source-labeled coefficient references, and MEAT documentation criteria for I21.0 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.