What is ICD-10 code I50.23?

I50.23 is the ICD-10-CM diagnosis code for Acute on chronic systolic (congestive) heart failure. A sudden worsening of a long-standing heart pumping problem where the left chamber cannot effectively move blood, causing acute symptoms on top of chronic disease. I50.23 is a billable code, meaning it can be reported on a claim as a primary or secondary diagnosis when supported by documentation. I50.23 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. I50.23 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. I50.23 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.

What is the V28 vs V24 difference for I50.23?

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 I50.23, V28 maps to Acute on Chronic Heart Failure at RAF 0.360 while V24 mapped to Congestive Heart Failure at RAF 0.331. Both models can still appear in legacy data and in payer-specific lookback periods.

What should coders know when reporting I50.23?

Requires documentation of both chronic systolic heart failure AND acute decompensation or exacerbation Look for terms like 'acute on chronic,' 'acute exacerbation of chronic,' or evidence of recent clinical deterioration Because I50.23 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.

I50.23: Acute on chronic systolic (congestive) heart failure — ICD-10 | Acute on Chronic Heart

ICD-10-CM Code View

HCC Buddy Code Card

Digital ICD-10 code-book layout with official code detail, always-visible risk models, Code Trumping, and Buddy coding guidance.

Code lookupI50.23Effective periodFY2026 Apr Update (Apr 1-Sep 30)

FY 2026 Apr update / Diseases of the circulatory system (I00-I99) / Other forms of heart disease (I30-I5A)

I50.23

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

Acute on chronic systolic (congestive) heart failure

A sudden worsening of a long-standing heart pumping problem where the left chamber cannot effectively move blood, causing acute symptoms on top of chronic disease.

Buddy Insight

Acute on chronic systolic congestive heart failure is one of the highest-acuity heart failure codes, representing acute decompensation superimposed on known chronic systolic dysfunction.

CMS-HCC V28

Mapped

HCC 224

Acute on Chronic Heart Failure

RAF 0.360

CMS-HCC V24

Mapped

HCC 85

Congestive Heart Failure

RAF 0.331

ACA/HHS

Not risk-adjusted for this model/period.

RAF 0

ESRD/PACE

Mapped

HCC 85

Congestive Heart Failure

RAF 0.0

RXHCC

Mapped

HCC 186

Heart Failure

RAF 0.0

Code Trumping

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Code Book Path

Official

I50Heart failure

I50.2Systolic (congestive) heart failure

I50.23Acute on chronic systolic (congestive) heart failure

Inclusion Terms

Official

Heart failure with reduced ejection fraction [HFrEF]
Systolic left ventricular heart failure

Excludes 2

Official

ICD-10-CM does not list Excludes 2 notes for I50.23 in this effective period.

Related Child Codes

Official

I50.20Unspecified systolic (congestive) heart failure

I50.21Acute systolic (congestive) heart failure

I50.22Chronic systolic (congestive) heart failure

Includes

Official

ICD-10-CM does not list Includes notes for I50.23 in this effective period.

Excludes 1

Official

combined systolic (congestive) and diastolic (congestive) heart failure (I50.4-)

Code First

Official

ICD-10-CM does not list Code First sequencing instructions for I50.23 in this effective period.

Use Additional

Official

ICD-10-CM does not list Use Additional Code instructions for I50.23 in this effective period.

Code Also

Official

end stage heart failure, if applicable (I50.84)

Buddy Documentation Tip

HCC Buddy guidance

Documentation must clearly indicate BOTH chronic systolic heart failure AND an acute exacerbation or decompensation

Evidence of chronic disease: history of heart failure, reduced ejection fraction, ongoing medications

Evidence of acute worsening: new or worsening symptoms, increased edema, respiratory distress, hospitalization

Precipitating factor for acute decompensation if identified

MEAT Support

HCC Buddy guidance

Documentation must clearly indicate BOTH chronic systolic heart failure AND an acute exacerbation or decompensation

Evidence of chronic disease: history of heart failure, reduced ejection fraction, ongoing medications

Evidence of acute worsening: new or worsening symptoms, increased edema, respiratory distress, hospitalization

Precipitating factor for acute decompensation if identified

Audit Caution

HCC Buddy guidance

Coding I50.21 (acute only) when the patient has known chronic heart failure — most acute episodes are actually acute on chronic

Using this code during stable outpatient visits after the acute episode has resolved — revert to I50.22

Failing to capture acute on chronic when documentation uses terms like 'decompensated heart failure' or 'heart failure exacerbation' in a patient with chronic disease

Not recognizing that this code carries the highest V28 RAF weight among systolic heart failure codes

Common Mistakes

HCC Buddy guidance

I50.21 — Acute systolic heart failure: use only for truly new onset acute disease without pre-existing chronic heart failure

I50.22 — Chronic systolic heart failure: use when chronic disease is stable without acute worsening

I50.43 — Acute on chronic combined systolic and diastolic heart failure: use when both systolic and diastolic components are documented

I50.33 — Acute on chronic diastolic heart failure: use when only diastolic dysfunction with acute exacerbation is documented

Last updated: FY2026 ICD-10-CM Apr update, Apr 1, 2026 through Sep 30, 2026. CMS-HCC V28 is 100% phased in for payment year 2026.

Is I50.23 an HCC code?

Yes. I50.23 maps to Acute on Chronic Heart Failure under the CMS-HCC V28 risk adjustment model (and Congestive Heart Failure under V24).

HCC Category Mapping

V28HCC 224, Acute on Chronic Heart Failure

0.360

V24HCC 85, Congestive Heart Failure

0.331

ESRDHCC 85, Congestive Heart Failure

0.000

RxHCCHCC 186, Heart Failure

0.000

RAF weights shown are the community, non-dual, aged base weights from the CMS risk adjustment model file. 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 I50.23 in the Code Book — tabular path, V28 RAF, and MEAT checklist →

MEAT Criteria for I50.23

For I50.23to 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 I50.23 during that encounter, not just copy-forwarded from a problem list.

Coder workflow notes

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What This Code Means

I50.23 is the ICD-10-CM diagnosis code for acute on chronic systolic (congestive) heart failure. A sudden worsening of a long-standing heart pumping problem where the left chamber cannot effectively move blood, causing acute symptoms on top of chronic disease. I50.23 sits in the ICD-10-CM chapter for diseases of the circulatory system (i00-i99), within the section covering other forms of heart disease (i30-i5a).

Under the CMS-HCC V28 risk adjustment model, I50.23 maps to Acute on Chronic Heart Failure (HCC 224) with a community, non-dual, aged base RAF weight of 0.360. Under the older CMS-HCC V24 model, I50.23 maps to Congestive Heart Failure (HCC 85) with a community, non-dual, aged base RAF weight of 0.331. 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.

Requires documentation of both chronic systolic heart failure AND acute decompensation or exacerbation. Because I50.23 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 I50.23 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.

Coding Tips

•Requires documentation of both chronic systolic heart failure AND acute decompensation or exacerbation
•Look for terms like 'acute on chronic,' 'acute exacerbation of chronic,' or evidence of recent clinical deterioration

Clinical Significance

Acute on chronic systolic congestive heart failure is one of the highest-acuity heart failure codes, representing acute decompensation superimposed on known chronic systolic dysfunction. These patients frequently require hospitalization, intravenous therapies, and intensive monitoring. This code carries the most significant risk adjustment weight among systolic heart failure codes in the V28 model.

Documentation Requirements

✓Documentation must clearly indicate BOTH chronic systolic heart failure AND an acute exacerbation or decompensation
✓Evidence of chronic disease: history of heart failure, reduced ejection fraction, ongoing medications
✓Evidence of acute worsening: new or worsening symptoms, increased edema, respiratory distress, hospitalization
✓Precipitating factor for acute decompensation if identified
✓Current treatment plan addressing both the acute episode and chronic management
✓Ejection fraction and functional status assessment

Commonly Confused Codes

•I50.21: Acute systolic heart failure: use only for truly new onset acute disease without pre-existing chronic heart failure
•I50.22: Chronic systolic heart failure: use when chronic disease is stable without acute worsening
•I50.43: Acute on chronic combined systolic and diastolic heart failure: use when both systolic and diastolic components are documented
•I50.33: Acute on chronic diastolic heart failure: use when only diastolic dysfunction with acute exacerbation is documented
•I50.813: Acute on chronic right heart failure: specifically right-sided heart failure