I22.1 ICD-10-CM Code: Subsequent ST elevation (STEMI) myocardial infarction of inferior wall
I22.1 maps to CMS-HCC V28 228. A source-labeled RAF reference is available. Confirm the documented diagnosis and applicable coding requirements. MEAT criteria · RAF Calculator · HCC coding software
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FY 2026 Apr update / Diseases of the circulatory system (I00-I99) / Ischemic heart diseases (I20-I25)
I22.1
Billable / SpecificICD-10-CMOfficial ICD-10-CMCodebook guidanceSubsequent ST elevation (STEMI) myocardial infarction of inferior wall
This code describes a second or recurring heart attack affecting the lower wall of the heart, where blood flow is severely blocked and the heart muscle is damaged. It is used when a patient has a subsequent STEMI (ST-elevation myocardial infarction) of the inferior wall after a previous heart attack.
Buddy Insight
Subsequent inferior wall STEMI indicates a second myocardial infarction affecting the bottom wall of the heart within 4 weeks of the initial event.
CMS-HCC V28
MappedHCC 228
Coefficient HCC 228: 0.252 (Community Non-Dual Aged (CNA))
CMS-HCC V24
HistoricalHistorical
Not used for CY2026 payment
ACA/HHS
MappedHCC 131
Code-level coefficient reference
ESRD/PACE
MappedHCC 86
Code-level coefficient reference
RXHCC
MappedHCC 188
Code-level coefficient reference
Code Book Path
Inclusion Terms
Official- Subsequent acute transmural myocardial infarction of inferior wall
- Subsequent transmural (Q wave) infarction (acute)(of) diaphragmatic wall
- Subsequent transmural (Q wave) infarction (acute)(of) inferior (wall) NOS
- Subsequent inferolateral transmural (Q wave) infarction (acute)
- Subsequent inferoposterior transmural (Q wave) infarction (acute)
Excludes 2
Official- certain conditions originating in the perinatal period (P04-P96)Inherited from I00-I99
- certain infectious and parasitic diseases (A00-B99)Inherited from I00-I99
- complications of pregnancy, childbirth and the puerperium (O00-O9A)Inherited from I00-I99
- congenital malformations, deformations, and chromosomal abnormalities (Q00-Q99)Inherited from I00-I99
- endocrine, nutritional and metabolic diseases (E00-E88)Inherited from I00-I99
- injury, poisoning and certain other consequences of external causes (S00-T88)Inherited from I00-I99
- neoplasms (C00-D49)Inherited from I00-I99
- symptoms, signs and abnormal clinical and laboratory findings, not elsewhere classified (R00-R94)Inherited from I00-I99
- systemic connective tissue disorders (M30-M36)Inherited from I00-I99
- transient cerebral ischemic attacks and related syndromes (G45.-)Inherited from I00-I99
Related Codes
Includes
Official- acute myocardial infarction occurring within four weeks (28 days) of a previous acute myocardial infarction, regardless of siteInherited from I22
- cardiac infarctionInherited from I22
- coronary (artery) embolismInherited from I22
- coronary (artery) occlusionInherited from I22
- coronary (artery) ruptureInherited from I22
- coronary (artery) thrombosisInherited from I22
- infarction of heart, myocardium, or ventricleInherited from I22
- recurrent myocardial infarctionInherited from I22
- reinfarction of myocardiumInherited from I22
- rupture of heart, myocardium, or ventricleInherited from I22
- subsequent type 1 myocardial infarctionInherited from I22
Excludes 1
Official- subsequent myocardial infarction, type 2 (I21.A1)Inherited from I22
- subsequent myocardial infarction of other type (type 3) (type 4) (type 5) (I21.A9)Inherited from I22
Code First
OfficialNo Code First sequencing instructions are included in this display for I22.1. Check the code and parent instructions in the Code Book.
Use Additional
Official- code, if applicable, to identify:Inherited from I22
- exposure to environmental tobacco smoke (Z77.22)Inherited from I22
- history of tobacco dependence (Z87.891)Inherited from I22
- occupational exposure to environmental tobacco smoke (Z57.31)Inherited from I22
- 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 I22
- tobacco dependence (F17.-)Inherited from I22
- tobacco use (Z72.0)Inherited from I22
Code Also
Official- the presence of hypertension (I10-I1A)Inherited from I20-I25
Buddy Documentation Tip
MEAT Support
Audit Caution
Common Mistakes
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 →
Is I22.1 an HCC code?
Yes. I22.1 (Subsequent ST elevation (STEMI) myocardial infarction of inferior wall) maps to HCC 228, Acute Myocardial Infarction under the CMS-HCC V28 risk adjustment model, with a source-labeled community non-dual aged reference coefficient of 0.252. Source-labeled code-level coefficients are references, not member totals. Actual contribution depends on complete member context, hierarchy and cleanup rules, interactions, and model year. HCC Buddy's RAF Calculator supports CMS-HCC V28 PY2026 and shows no score unless every required source and calculation check passes. It is billable for payment year 2026.
Coder answer: I22.1 is billable and maps to V28 HCC 228, Acute Myocardial Infarction. Open it in the Code Book for the tabular path, RAF, and MEAT checklist.
- Code
- I22.1
- Description
- Subsequent ST elevation (STEMI) myocardial infarction of inferior wall
- HCC (V28)
- HCC 228 — Acute Myocardial Infarction
- RAF reference coefficient
- 0.252
- Billable
- Yes
- Payment year
- 2026
HCC Category Mapping
These are source-labeled model coefficients, not member totals. A category may still be removed by hierarchy or model cleanup rules. Weights are not directly comparable across models: CMS-HCC V28 and V24 use Community, Non-Dual, Aged; ESRD uses the dialysis continuing-enrollee model; RxHCC is the Part D continuing-enrollee, non-low-income, aged weight (a larger scale than CMS-HCC). ACA/HHS has no single weight — it varies by metal level. Actual per-patient RAF contribution depends on member context, hierarchy and cleanup rules, interactions, and the model year used by the payer. V28 is the CMS-HCC model phased in over payment years 2024–2026; V24 remains available for historical review.
Work I22.1 in the Code Book — tabular path, V28 RAF reference, and MEAT checklist →
MEAT review for I22.1
For I22.1, confirm that the documentation supports the diagnosis and meets the applicable coding, encounter, program and payer requirements. MEAT (Monitor, Evaluate, Assess, or Treat) is a review mnemonic, not a universal CMS coding rule.
- MMonitor: signs, symptoms, disease progression, or lab trending documented in the note
- EEvaluate: test results, medication response, or physical findings reviewed by the provider
- AAssess: explicit mention in the assessment or plan with acknowledgment of status
- TTreat: medication, referral, procedure, therapy, or counseling tied to the diagnosis
Coder workflow notes
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What This Code Means
I22.1 is the ICD-10-CM diagnosis code for subsequent st elevation (stemi) myocardial infarction of inferior wall. This code describes a second or recurring heart attack affecting the lower wall of the heart, where blood flow is severely blocked and the heart muscle is damaged. It is used when a patient has a subsequent STEMI (ST-elevation myocardial infarction) of the inferior wall after a previous heart attack. I22.1 sits in the ICD-10-CM chapter for diseases of the circulatory system (i00-i99), within the section covering ischemic heart diseases (i20-i25).
Under the CMS-HCC V28 risk adjustment model, I22.1 maps to Acute Myocardial Infarction (HCC 228) with a source-labeled community, non-dual, aged reference coefficient of 0.252. For CY2026 non-PACE Medicare Advantage, CMS uses 100% of the 2024 CMS-HCC model (V28). PACE uses a separate model blend. Source-labeled code-level coefficients are references, not member totals. Actual contribution depends on complete member context, hierarchy and cleanup rules, interactions, and model year. HCC Buddy's RAF Calculator supports CMS-HCC V28 PY2026 and shows no score unless every required source and calculation check passes.
The 'I22' category is specifically for subsequent MIs occurring within 4 weeks of a previous MI; verify the timing and location documentation in the medical record. For I22.1, confirm that the documentation supports the diagnosis and meets the applicable coding, encounter, program and payer requirements. MEAT (Monitor, Evaluate, Assess, or Treat) is a review mnemonic, not a universal CMS coding rule. When documentation is ambiguous, coders should issue a provider query rather than assume the highest-specificity variant.
HCC Buddy maintains structured V28 and V24 mapping, source-labeled coefficient references, and MEAT documentation criteria for I22.1 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.
Coding Tips
- •The 'I22' category is specifically for subsequent MIs occurring within 4 weeks of a previous MI; verify the timing and location documentation in the medical record
- •Ensure the inferior wall location is clearly documented and distinguish from other wall locations (anterior, lateral, posterior) as each has different codes
Clinical Significance
Subsequent inferior wall STEMI indicates a second myocardial infarction affecting the bottom wall of the heart within 4 weeks of the initial event. This recurrence carries high prognostic significance as it reflects ongoing coronary instability, particularly in the right coronary artery or left circumflex territory. These patients typically require urgent re-evaluation and may need emergent cardiac catheterization.
Documentation Requirements
- ✓Documentation confirming a second or subsequent myocardial infarction
- ✓Timing within 4 weeks of the initial myocardial infarction event
- ✓Inferior wall location clearly documented
- ✓Electrocardiogram showing new inferior ST elevation (leads II, III, aVF)
- ✓Re-elevation of cardiac biomarkers
- ✓Both initial (I21.x) and subsequent (I22.1) codes must be assigned
Commonly Confused Codes
- •I21.11: Initial STEMI of right coronary artery (inferior wall): for the first event
- •I21.19: Initial STEMI of other coronary artery of inferior wall: for the first event
- •I22.0: Subsequent STEMI of anterior wall: different wall location
- •I22.2: Subsequent NSTEMI: different electrocardiogram presentation
- •I22.9: Subsequent STEMI of unspecified site: use when wall location unknown