What is ICD-10 code I50.33?

I50.33 is the ICD-10-CM diagnosis code for Acute on chronic diastolic (congestive) heart failure. A sudden worsening of a long-standing diastolic heart condition where the stiffened heart muscle cannot relax or fill properly, causing acute symptoms. I50.33 is a billable code, meaning it can be reported on a claim as a primary or secondary diagnosis when supported by documentation. I50.33 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. I50.33 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. I50.33 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 I50.33 map to under V28?

I50.33 maps to CMS-HCC V28 224 (Acute on Chronic Heart Failure). The category number and label come from the CMS-HCC V28 model file for payment year 2026.

What does I50.33 pay in RAF?

I50.33 carries a community, non-dual, aged (CNA) RAF weight of 0.360 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 I50.33?

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 I50.33, 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 documentation supports I50.33?

Documentation must show both chronic diastolic HF and a current acute exacerbation. A stable follow-up for HFpEF is I50.32, not I50.33. Do not default to I50.33 for any symptomatic HFpEF patient, the acute component must be explicit (decompensation, volume overload, ED visit for HF symptoms attributed to diastolic dysfunction). V28 HCC 224 (Acute on Chronic Heart Failure) at RAF 0.36. Acute-on-chronic diastolic HF maps to HCC 224, not the chronic-HF HCC 226 that I50.32 carries, though the community coefficient is the same. Because I50.33 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 I50.33: Acute on chronic

I50.33 maps to CMS-HCC V28 224 (RAF 0.360). Documentation must support MEAT. MEAT criteria · RAF calculator · HCC coding software

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Code lookupI50.33Effective 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)

I50.33

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

Acute on chronic diastolic (congestive) heart failure

A sudden worsening of a long-standing diastolic heart condition where the stiffened heart muscle cannot relax or fill properly, causing acute symptoms.

Buddy Insight

Acute on chronic diastolic congestive heart failure represents acute decompensation superimposed on known chronic diastolic 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

Mapped

HCC 130

HHS-HCC 130

Varies by metal level

ESRD/PACE

Mapped

HCC 85

Congestive Heart Failure

RAF 0.063

RXHCC

Mapped

HCC 186

Heart Failure

RAF 0.110

Code Book Path

Official

I50Heart failure

I50.3Diastolic (congestive) heart failure

I50.33Acute on chronic diastolic (congestive) heart failure

Inclusion Terms

Official

Diastolic left ventricular heart failure
Heart failure with normal ejection fraction
Heart failure with preserved ejection fraction [HFpEF]

Excludes 2

Official

ICD-10-CM does not list Excludes 2 notes for I50.33 in this effective period.

Related Child Codes

Official

I50.30Unspecified diastolic (congestive) heart failure

I50.31Acute diastolic (congestive) heart failure

I50.32Chronic diastolic (congestive) heart failure

Includes

Official

ICD-10-CM does not list Includes notes for I50.33 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 I50.33 in this effective period.

Use Additional

Official

ICD-10-CM does not list Use Additional Code instructions for I50.33 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 diastolic heart failure AND acute exacerbation or decompensation

Evidence of chronic disease: history of diastolic heart failure, prior echocardiograms showing diastolic dysfunction

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

Preserved ejection fraction with elevated filling pressures or brain natriuretic peptide levels

MEAT Support

HCC Buddy guidance

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

Evidence of chronic disease: history of diastolic heart failure, prior echocardiograms showing diastolic dysfunction

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

Preserved ejection fraction with elevated filling pressures or brain natriuretic peptide levels

Audit Caution

HCC Buddy guidance

Coding I50.31 (acute only) when patient has known chronic diastolic heart failure

Using this code during stable outpatient visits after acute episode resolution — revert to I50.32

Missing the acute on chronic designation when documentation says 'heart failure exacerbation' in known chronic patient

Not recognizing this is the only diastolic heart failure code with a V28 RAF weight

Common Mistakes

HCC Buddy guidance

I50.31 — Acute diastolic heart failure: use only for new onset acute disease without chronic heart failure history

I50.32 — Chronic diastolic heart failure: use when chronic disease is stable without acute worsening

I50.23 — Acute on chronic systolic heart failure: use when systolic dysfunction (reduced ejection fraction) is specified

I50.43 — Acute on chronic combined systolic and diastolic heart failure: use when both types are 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 I50.33 an HCC code?

Yes. I50.33 (Acute on chronic diastolic (congestive) heart failure) maps to Acute on Chronic Heart Failure under the CMS-HCC V28 risk adjustment model (and Congestive Heart Failure under V24), with a community non-dual aged RAF of 0.360. It is billable for payment year 2026.

Coder answer: I50.33 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: I50.33
Description: Acute on chronic diastolic (congestive) heart failure
HCC (V28): HCC 224 — Acute on Chronic Heart Failure
RAF: 0.360
Billable: Yes
Payment year: 2026

HCC Category Mapping

V28HCC 224, Acute on Chronic Heart Failure

0.360

V24HCC 85, Congestive Heart Failure

0.331

ESRDHCC 85, Congestive Heart Failure

0.063

RxHCCHCC 186, Heart Failure

0.110

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 I50.33 in the Code Book — tabular path, V28 RAF, and MEAT checklist →

MEAT Criteria for I50.33

For I50.33 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 I50.33 during that encounter, not just copy-forwarded from a problem list.

Coder workflow notes

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What This Code Means

I50.33 is the ICD-10-CM diagnosis code for acute on chronic diastolic (congestive) heart failure. A sudden worsening of a long-standing diastolic heart condition where the stiffened heart muscle cannot relax or fill properly, causing acute symptoms. I50.33 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, I50.33 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, I50.33 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.

Documentation must show both chronic diastolic HF and a current acute exacerbation. A stable follow-up for HFpEF is I50.32, not I50.33. Because I50.33 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 I50.33 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.

Coding Tips

•Documentation must show both chronic diastolic HF and a current acute exacerbation. A stable follow-up for HFpEF is I50.32, not I50.33.
•Do not default to I50.33 for any symptomatic HFpEF patient, the acute component must be explicit (decompensation, volume overload, ED visit for HF symptoms attributed to diastolic dysfunction).
•V28 HCC 224 (Acute on Chronic Heart Failure) at RAF 0.36. Acute-on-chronic diastolic HF maps to HCC 224, not the chronic-HF HCC 226 that I50.32 carries, though the community coefficient is the same.

Clinical Significance

Acute on chronic diastolic congestive heart failure represents acute decompensation superimposed on known chronic diastolic dysfunction. This is one of the most clinically significant heart failure codes, reflecting patients with the highest resource utilization including hospitalizations and intensive outpatient management. It carries the highest V28 RAF weight among diastolic heart failure codes.

Documentation Requirements

✓Documentation must clearly indicate BOTH chronic diastolic heart failure AND acute exacerbation or decompensation
✓Evidence of chronic disease: history of diastolic heart failure, prior echocardiograms showing diastolic dysfunction
✓Evidence of acute worsening: new or worsening symptoms, increased edema, respiratory distress
✓Preserved ejection fraction with elevated filling pressures or brain natriuretic peptide levels
✓Precipitating factor for acute decompensation if identified
✓Treatment plan addressing both acute episode and chronic management

Commonly Confused Codes

•I50.31: Acute diastolic heart failure: use only for new onset acute disease without chronic heart failure history
•I50.32: Chronic diastolic heart failure: use when chronic disease is stable without acute worsening
•I50.23: Acute on chronic systolic heart failure: use when systolic dysfunction (reduced ejection fraction) is specified
•I50.43: Acute on chronic combined systolic and diastolic heart failure: use when both types are documented
•I50.813: Acute on chronic right heart failure: right-sided heart failure specifically