What is ICD-10 code I22.0?

I22.0 is the ICD-10-CM diagnosis code for Subsequent ST elevation (STEMI) myocardial infarction of anterior wall. A second heart attack occurring within 4 weeks of the first one, affecting the front wall of the heart with ST segment elevation on the EKG. I22.0 is a billable code, meaning it can be reported on a claim as a primary or secondary diagnosis when supported by documentation. I22.0 is part of the FY2026 ICD-10-CM code set published by the CMS National Center for Health Statistics and used on Medicare, Medicaid, and commercial claims in the United States.

Yes. I22.0 is a billable ICD-10-CM code that can be reported on professional and institutional claims as a primary or secondary diagnosis when the provider documentation supports the specific condition described. Billable codes in ICD-10-CM are coded to the highest level of specificity available for the documented diagnosis. I22.0 is current for fiscal year 2026 and remains in the active CMS ICD-10-CM code set published by the National Center for Health Statistics.

Which HCC does I22.0 map to under V28?

I22.0 maps to CMS-HCC V28 228 (Acute Myocardial Infarction). The category number and label come from the CMS-HCC V28 model file for payment year 2026.

What does I22.0 pay in RAF?

I22.0 carries a community, non-dual, aged (CNA) RAF weight of 0.252 under CMS-HCC V28 for payment year 2026. The weight comes from the CMS V28 relative-factor file, not a hand-typed table.

What is the V28 vs V24 difference for I22.0?

CMS phased in the V28 risk adjustment model over payment years 2024 (33%), 2025 (67%), and 2026 (100%), replacing V24. V28 consolidates HCC categories, removes some lower-acuity conditions, and recalibrates RAF weights across the entire model. For I22.0, V28 maps to Acute Myocardial Infarction at RAF 0.252 while V24 mapped to Acute Myocardial Infarction at RAF 0.195. Both models can still appear in legacy data and in payer-specific lookback periods.

What documentation supports I22.0?

Code I22 is used only for recurrent MI within 4 weeks of the initial event; verify the timing in the medical record Ensure documentation clearly indicates this is a subsequent/recurrent MI and not the initial event Because I22.0 maps to a payment HCC, the documentation must also satisfy MEAT criteria (Monitor, Evaluate, Assess, or Treat) for the encounter to count toward the patient's risk adjustment score. See the MEAT criteria checklist at /meat-criteria for what Monitor, Evaluate, Assess, or Treat looks like in a note. MEAT is generic documentation evidence, not a payer-specific rule.

2026 ICD-10-CM I22.0: Subsequent ST elevation

I22.0 maps to CMS-HCC V28 228 (RAF 0.252). Documentation must support MEAT. MEAT criteria · RAF calculator · HCC Buddy coding tools

ICD-10-CM Code View

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Code lookupI22.0Effective periodFY2026 Apr Update (Apr 1-Sep 30)

FY 2026 Apr update / Diseases of the circulatory system (I00-I99) / Ischemic heart diseases (I20-I25)

I22.0

Billable / SpecificICD-10-CMOfficial ICD-10-CMCodebook guidance

Subsequent ST elevation (STEMI) myocardial infarction of anterior wall

A second heart attack occurring within 4 weeks of the first one, affecting the front wall of the heart with ST segment elevation on the EKG.

Buddy Insight

Subsequent anterior wall STEMI indicates a recurrent myocardial infarction occurring within 4 weeks of the initial event, which significantly increases mortality risk and resource utilization.

CMS-HCC V28

Mapped

HCC 228

Acute Myocardial Infarction

RAF 0.252

CMS-HCC V24

Mapped

HCC 86

Acute Myocardial Infarction

RAF 0.195

ACA/HHS

Mapped

HCC 131

HHS-HCC 131

Varies by metal level

ESRD/PACE

Mapped

HCC 86

Acute Myocardial Infarction

RAF 0.151

RXHCC

Mapped

HCC 188

Coronary Artery Disease and A...

RAF 0.052

Code Book Path

Official

I22Subsequent ST elevation (STEMI) and non-ST elevation (NSTEMI) myocardial infarction

I22.0Subsequent ST elevation (STEMI) myocardial infarction of anterior wall

Inclusion Terms

Official

Subsequent acute transmural myocardial infarction of anterior wall
Subsequent transmural (Q wave) infarction (acute)(of) anterior (wall) NOS
Subsequent anteroapical transmural (Q wave) infarction (acute)
Subsequent anterolateral transmural (Q wave) infarction (acute)
Subsequent anteroseptal transmural (Q wave) infarction (acute)

Excludes 2

Official

ICD-10-CM does not list Excludes 2 notes for I22.0 in this effective period.

Related Child Codes

Official

I22.1Subsequent ST elevation (STEMI) myocardial infarction of inferior wall

I22.2Subsequent non-ST elevation (NSTEMI) myocardial infarction

I22.8Subsequent ST elevation (STEMI) myocardial infarction of other sites

I22.9Subsequent ST elevation (STEMI) myocardial infarction of unspecified site

Includes

Official

acute myocardial infarction occurring within four weeks (28 days) of a previous acute myocardial infarction, regardless of site
cardiac infarction
coronary (artery) embolism
coronary (artery) occlusion
coronary (artery) rupture

Excludes 1

Official

subsequent myocardial infarction, type 2 (I21.A1)
subsequent myocardial infarction of other type (type 3) (type 4) (type 5) (I21.A9)

Code First

Official

ICD-10-CM does not list Code First sequencing instructions for I22.0 in this effective period.

Use Additional

Official

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)

Code Also

Official

ICD-10-CM does not list Code Also instructions for I22.0 in this effective period.

Buddy Documentation Tip

HCC Buddy guidance

Documentation of a second or subsequent myocardial infarction

Timing confirmation that the subsequent event occurs within 4 weeks of the initial myocardial infarction

Anterior wall location documented

Electrocardiogram showing new or recurrent ST elevation in anterior leads

MEAT Support

HCC Buddy guidance

Documentation of a second or subsequent myocardial infarction

Timing confirmation that the subsequent event occurs within 4 weeks of the initial myocardial infarction

Anterior wall location documented

Electrocardiogram showing new or recurrent ST elevation in anterior leads

Audit Caution

HCC Buddy guidance

Using I21 codes for a recurrent myocardial infarction within 4 weeks instead of I22

Failing to assign both the initial (I21.x) and subsequent (I22.0) myocardial infarction codes

Confusing 'subsequent' as meaning 'old' — I22 codes are for acute recurrent events

Using I22 codes beyond the 4-week window when they no longer apply

Common Mistakes

HCC Buddy guidance

I21.01, I21.02, I21.09 — Initial anterior wall STEMI codes: for the first event, not recurrence

I22.1 — Subsequent STEMI of inferior wall: different wall location

I22.9 — Subsequent STEMI of unspecified site: use only when wall location is not documented

I25.2 — Old myocardial infarction: for healed myocardial infarction beyond acute phase

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 I22.0 an HCC code?

Yes. I22.0 (Subsequent ST elevation (STEMI) myocardial infarction of anterior wall) maps to Acute Myocardial Infarction under the CMS-HCC V28 risk adjustment model (and Acute Myocardial Infarction under V24), with a community non-dual aged RAF of 0.252. It is billable for payment year 2026.

Coder answer: I22.0 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: I22.0
Description: Subsequent ST elevation (STEMI) myocardial infarction of anterior wall
HCC (V28): HCC 228 — Acute Myocardial Infarction
RAF: 0.252
Billable: Yes
Payment year: 2026

HCC Category Mapping

V28HCC 228, Acute Myocardial Infarction

0.252

V24HCC 86, Acute Myocardial Infarction

0.195

ESRDHCC 86, Acute Myocardial Infarction

0.151

RxHCCHCC 188, Coronary Artery Disease and Angina

0.052

Each model's RAF is its CMS base weight for that model's standard population, so 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 segment, interactions, and the model year used by the payer. V28 is the CMS-HCC model phased in over payment years 2024–2026; V24 remains in use during the transition and for historical data.

Work I22.0 in the Code Book — tabular path, V28 RAF, and MEAT checklist →

MEAT Criteria for I22.0

For I22.0 to count as a valid HCC diagnosis in a given encounter, the provider's documentation must show MEAT: Monitor, Evaluate, Assess, or Treat. A diagnosis from a prior year does not carry forward automatically, it has to be re-documented and supported each calendar year.

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

Only one of M/E/A/T is required to support the code, but the documentation must be specific enough to show that the provider actually addressed I22.0 during that encounter, not just copy-forwarded from a problem list.

Coder workflow notes

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What This Code Means

I22.0 is the ICD-10-CM diagnosis code for subsequent st elevation (stemi) myocardial infarction of anterior wall. A second heart attack occurring within 4 weeks of the first one, affecting the front wall of the heart with ST segment elevation on the EKG. I22.0 sits in the ICD-10-CM chapter for diseases of the circulatory system (i00-i99), within the section covering ischemic heart diseases (i20-i25).

Under the CMS-HCC V28 risk adjustment model, I22.0 maps to Acute Myocardial Infarction (HCC 228) with a community, non-dual, aged base RAF weight of 0.252. Under the older V24 model, I22.0 mapped to the same category but with a base RAF weight of 0.195, V28 recalibrated weights across the entire model. V28 is the CMS-HCC risk adjustment model that reached 100% phase-in for payment year 2026, replacing V24 which was used during the PY2024–PY2025 transition.

Code I22 is used only for recurrent MI within 4 weeks of the initial event; verify the timing in the medical record. Because I22.0 maps to a payment HCC, the provider's documentation must satisfy MEAT criteria (Monitor, Evaluate, Assess, or Treat) for the encounter to count toward the patient's Medicare Advantage risk adjustment score. 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, RAF weights, and MEAT documentation criteria for I22.0 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.

Coding Tips

•Code I22 is used only for recurrent MI within 4 weeks of the initial event; verify the timing in the medical record
•Ensure documentation clearly indicates this is a subsequent/recurrent MI and not the initial event

Clinical Significance

Subsequent anterior wall STEMI indicates a recurrent myocardial infarction occurring within 4 weeks of the initial event, which significantly increases mortality risk and resource utilization. A second myocardial infarction during the acute recovery phase suggests ongoing coronary instability and often necessitates more aggressive intervention. Accurate coding of subsequent events is essential for reflecting true disease severity.

Documentation Requirements

✓Documentation of a second or subsequent myocardial infarction
✓Timing confirmation that the subsequent event occurs within 4 weeks of the initial myocardial infarction
✓Anterior wall location documented
✓Electrocardiogram showing new or recurrent ST elevation in anterior leads
✓New cardiac biomarker elevation above the declining baseline from the initial event
✓Both the initial myocardial infarction code (I21.x) and subsequent code (I22.0) should be assigned

Commonly Confused Codes

•I21.01, I21.02, I21.09: Initial anterior wall STEMI codes: for the first event, not recurrence
•I22.1: Subsequent STEMI of inferior wall: different wall location
•I22.9: Subsequent STEMI of unspecified site: use only when wall location is not documented
•I25.2: Old myocardial infarction: for healed myocardial infarction beyond acute phase