What is ICD-10 code B33.24?

B33.24 is the ICD-10-CM diagnosis code for Viral cardiomyopathy. Viral cardiomyopathy is weakening of the heart muscle caused by a viral infection, which reduces the heart's ability to pump blood throughout the body. It belongs to the ICD-10-CM chapter for certain infectious and parasitic diseases (a00-b99). B33.24 is a billable code, meaning it can be reported on a claim as a primary or secondary diagnosis when supported by documentation. B33.24 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. B33.24 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. B33.24 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 B33.24?

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 B33.24, V28 maps to Cardiomyopathy/Myocarditis at RAF 0.189 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 B33.24?

Document the ejection fraction or functional class if available to indicate severity Specify if this is acute or chronic cardiomyopathy, as this affects treatment and prognosis Because B33.24 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.

2026 ICD-10-CM B33.24: Viral cardiomyopathy

ICD-10-CM Code View

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Code lookupB33.24Effective periodFY2026 Apr Update (Apr 1-Sep 30)

FY 2026 Apr update / Certain infectious and parasitic diseases (A00-B99) / Other viral diseases (B25-B34)

B33.24

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

Viral cardiomyopathy

Viral cardiomyopathy is weakening of the heart muscle caused by a viral infection, which reduces the heart's ability to pump blood throughout the body.

Buddy Insight

Viral cardiomyopathy is heart muscle disease caused by viral infection, most commonly coxsackievirus B, adenovirus, or parvovirus B19.

CMS-HCC V28

Mapped

HCC 227

Cardiomyopathy/Myocarditis

RAF 0.189

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

B33Other viral diseases, not elsewhere classified

B33.2Viral carditis

B33.24Viral cardiomyopathy

Inclusion Terms

Official

Coxsackie (virus) carditis

Excludes 2

Official

ICD-10-CM does not list Excludes 2 notes for B33.24 in this effective period.

Related Child Codes

Official

B33.20Viral carditis, unspecified

B33.21Viral endocarditis

B33.22Viral myocarditis

B33.23Viral pericarditis

Includes

Official

ICD-10-CM does not list Includes notes for B33.24 in this effective period.

Excludes 1

Official

ICD-10-CM does not list Excludes 1 notes for B33.24 in this effective period.

Code First

Official

ICD-10-CM does not list Code First sequencing instructions for B33.24 in this effective period.

Use Additional

Official

ICD-10-CM does not list Use Additional Code instructions for B33.24 in this effective period.

Code Also

Official

ICD-10-CM does not list Code Also instructions for B33.24 in this effective period.

Buddy Documentation Tip

HCC Buddy guidance

Viral etiology confirmed or strongly suspected (endomyocardial biopsy with viral PCR, or clinical diagnosis with supporting serology)

Echocardiographic findings: left ventricular ejection fraction, chamber dimensions, wall motion abnormalities

Heart failure classification if applicable (NYHA class I-IV)

Specific virus identified if known (coxsackievirus, adenovirus, parvovirus, influenza, SARS-CoV-2)

MEAT Support

HCC Buddy guidance

Viral etiology confirmed or strongly suspected (endomyocardial biopsy with viral PCR, or clinical diagnosis with supporting serology)

Echocardiographic findings: left ventricular ejection fraction, chamber dimensions, wall motion abnormalities

Heart failure classification if applicable (NYHA class I-IV)

Specific virus identified if known (coxsackievirus, adenovirus, parvovirus, influenza, SARS-CoV-2)

Audit Caution

HCC Buddy guidance

Coding idiopathic dilated cardiomyopathy (I42.0) when a viral etiology has been documented — this changes HCC mapping

Confusing viral myocarditis (acute inflammation) with viral cardiomyopathy (structural heart muscle disease) — myocarditis may evolve into cardiomyopathy

Not documenting the ejection fraction, which is critical for clinical staging and may trigger additional coding opportunities

Missing the viral etiology when a patient presents with new-onset heart failure following a viral illness

Common Mistakes

HCC Buddy guidance

I42.0 (Dilated cardiomyopathy) — Idiopathic or non-infectious dilated cardiomyopathy; B33.24 specifies viral etiology

I40.0 (Infective myocarditis) — Acute myocarditis is inflammation; cardiomyopathy implies structural/functional changes that may persist after acute inflammation resolves

I25.5 (Ischemic cardiomyopathy) — Heart muscle disease from coronary artery disease, not viral infection

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 B33.24 an HCC code?

Yes. B33.24 (Viral cardiomyopathy) maps to Cardiomyopathy/Myocarditis under the CMS-HCC V28 risk adjustment model (and Congestive Heart Failure under V24), with a community non-dual aged RAF of 0.189. It is billable for payment year 2026.

Coder answer: B33.24 is billable and maps to V28 HCC 227, Cardiomyopathy/Myocarditis. Open it in the Code Book for the tabular path, RAF, and MEAT checklist.

Code: B33.24
Description: Viral cardiomyopathy
HCC (V28): HCC 227 — Cardiomyopathy/Myocarditis
RAF: 0.189
Billable: Yes
Payment year: 2026

HCC Category Mapping

V28HCC 227, Cardiomyopathy/Myocarditis

0.189

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 B33.24 in the Code Book — tabular path, V28 RAF, and MEAT checklist →

MEAT Criteria for B33.24

For B33.24 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 B33.24 during that encounter, not just copy-forwarded from a problem list.

Coder workflow notes

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What This Code Means

B33.24 is the ICD-10-CM diagnosis code for viral cardiomyopathy. Viral cardiomyopathy is weakening of the heart muscle caused by a viral infection, which reduces the heart's ability to pump blood throughout the body. B33.24 sits in the ICD-10-CM chapter for certain infectious and parasitic diseases (a00-b99), within the section covering other viral diseases (b25-b34).

Under the CMS-HCC V28 risk adjustment model, B33.24 maps to Cardiomyopathy/Myocarditis (HCC 227) with a community, non-dual, aged base RAF weight of 0.189. Under the older CMS-HCC V24 model, B33.24 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.

Document the ejection fraction or functional class if available to indicate severity. Because B33.24 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 B33.24 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.

Coding Tips

•Document the ejection fraction or functional class if available to indicate severity
•Specify if this is acute or chronic cardiomyopathy, as this affects treatment and prognosis

Clinical Significance

Viral cardiomyopathy is heart muscle disease caused by viral infection, most commonly coxsackievirus B, adenovirus, or parvovirus B19. It is a leading cause of dilated cardiomyopathy in younger patients and can progress to heart failure requiring transplant. Accurate capture reflects both the infectious etiology and the cardiac dysfunction burden.

Documentation Requirements

✓Viral etiology confirmed or strongly suspected (endomyocardial biopsy with viral PCR, or clinical diagnosis with supporting serology)
✓Echocardiographic findings: left ventricular ejection fraction, chamber dimensions, wall motion abnormalities
✓Heart failure classification if applicable (NYHA class I-IV)
✓Specific virus identified if known (coxsackievirus, adenovirus, parvovirus, influenza, SARS-CoV-2)
✓Treatment plan: heart failure medications, activity restrictions, cardiac monitoring

Commonly Confused Codes

•I42.0 (Dilated cardiomyopathy): Idiopathic or non-infectious dilated cardiomyopathy; B33.24 specifies viral etiology
•I40.0 (Infective myocarditis): Acute myocarditis is inflammation; cardiomyopathy implies structural/functional changes that may persist after acute inflammation resolves
•I25.5 (Ischemic cardiomyopathy): Heart muscle disease from coronary artery disease, not viral infection