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.

Which HCC does I50.23 map to under V28?

I50.23 maps to CMS-HCC V28 HCC 224 (Acute on Chronic Heart Failure). The category numbers, labels, and conditions come from the CMS-HCC V28 model file for payment year 2026.

What documentation supports I50.23?

Documentation must establish both the chronic systolic HF baseline and a current acute exacerbation, a symptomatic worsening, an ED visit, a diuretic dose adjustment, or hospital admission narrative tied to the underlying chronic HF. Do not use I50.23 for a routine stable follow-up on a chronic systolic HF patient, that is I50.22. Acute-on-chronic requires the acute component documented by the provider. V28 HCC 224 (Acute on Chronic Heart Failure) at RAF 0.36. Acute-on-chronic systolic HF maps to its own HCC, distinct from chronic HF (226) and acute HF (225), though the community coefficient matches. Because I50.23 maps to an HCC category, the documentation must satisfy MEAT criteria (Monitor, Evaluate, Assess, or Treat) before the diagnosis is used for risk adjustment. 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 I50.23: Acute on chronic systolic

I50.23 maps to CMS-HCC V28 224. A source-labeled RAF reference is available. Documentation must support MEAT. MEAT criteria · RAF Calculator · HCC Buddy coding tools

ICD-10-CM Code View

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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

Code-level coefficient reference

CMS-HCC V24

Historical

Not used for standard CY2026 Medicare Advantage payment. Select a historical period to review V24.

Not used for CY2026 payment

ACA/HHS

Mapped

HCC 130

HHS-HCC 130 adult, RAF varies...

Code-level coefficient reference

ESRD/PACE

Mapped

HCC 85

Congestive Heart Failure

Code-level coefficient reference

RXHCC

Mapped

HCC 186

Heart Failure

Code-level coefficient reference

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

Missing the provider's documentation of acute worsening within notes describing chronic management

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

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 I50.23 an HCC code?

Yes. I50.23 (Acute on chronic systolic (congestive) heart failure) maps to HCC 224, Acute on Chronic Heart Failure under the CMS-HCC V28 risk adjustment model, with a source-labeled community non-dual aged reference coefficient of 0.360. 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: I50.23 is billable and maps to V28 HCC 224, Acute on Chronic Heart Failure. Open it in the Code Book for the tabular path, RAF, and MEAT checklist.

Code: I50.23
Description: Acute on chronic systolic (congestive) heart failure
HCC (V28): HCC 224 — Acute on Chronic Heart Failure
RAF reference coefficient: 0.360
Billable: Yes
Payment year: 2026

HCC Category Mapping

V28HCC 224, Acute on Chronic Heart Failure

0.360

ESRDHCC 85, Congestive Heart Failure

Not separately weighted

RxHCCHCC 186, Heart Failure

Not separately weighted

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 I50.23 in the Code Book — tabular path, V28 RAF reference, and MEAT checklist →

MEAT Criteria for I50.23

For I50.23 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 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 source-labeled community, non-dual, aged reference coefficient of 0.360. No V24 mapping is shown for I50.23; use the applicable model and payment year when reviewing the V28 mapping. 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. 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.

Documentation must establish both the chronic systolic HF baseline and a current acute exacerbation, a symptomatic worsening, an ED visit, a diuretic dose adjustment, or hospital admission narrative tied to the underlying chronic HF. Because I50.23 maps to an HCC category, the provider's documentation must satisfy MEAT criteria (Monitor, Evaluate, Assess, or Treat) before the diagnosis is used for risk adjustment. 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 I50.23 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.

Coding Tips

•Documentation must establish both the chronic systolic HF baseline and a current acute exacerbation, a symptomatic worsening, an ED visit, a diuretic dose adjustment, or hospital admission narrative tied to the underlying chronic HF.
•Do not use I50.23 for a routine stable follow-up on a chronic systolic HF patient, that is I50.22. Acute-on-chronic requires the acute component documented by the provider.
•Acute-on-chronic systolic HF maps to its own HCC, distinct from chronic HF (226) and acute HF (225), though the community coefficient matches.

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