ICD-10 I51.4
Billable / Specific HCC v28: 85Myocarditis, unspecified
About ICD-10-CM I51.4
ICD-10-CM code I51.4 represents Myocarditis, unspecified. This is a billable/specific code in the Circulatory System chapter (block I51). The 2026 edition of ICD-10-CM I51.4 became effective on October 1, 2025.
Coding Tips for I51.4
Specialist guidance from the PayerReady Medical Coding Team. Specificity warnings, HCC capture rules, sequencing notes.
I51.4 is a CMS-HCC v28 risk-adjustment code (category 85). To count for the patient Risk Adjustment Factor (RAF), document the diagnosis with MEAT language each calendar year: Monitored, Evaluated, Assessed, Treated. A diagnosis on the problem list alone does not satisfy CMS RADV audit standards. Include the diagnosis in the assessment with current status and current treatment plan.
Inclusion Terms / Approximate Synonyms
Clinical terms and conditions classified under I51.4. Per CMS ICD-10-CM Tabular 2026.
- Chronic (interstitial) myocarditis
- Myocardial fibrosis
- Myocarditis NOS
Type 1 Excludes
Pure excludes, these codes can never be coded together with I51.4. The conditions are mutually exclusive (e.g., congenital vs acquired forms).
- acute or subacute myocarditis (I40.-)
Medicare Advantage HCC Impact
Capture this diagnosis annually for accurate risk adjustment. Missed HCC captures are the #1 revenue leak in Medicare Advantage risk programs.
Medicare LCD Coverage for I51.4
Local Coverage Determinations (LCDs) from CMS MACs that list I51.4 as a covered diagnosis.
Showing top 10 of 281 total . Click a CPT for full coverage scope.
Commercial Payer Coverage
Coverage policies from major commercial payers referencing I51.4.
4 Aetna
2 Cigna
5 Medicare
CPT Codes Commonly Billed with I51.4
Procedures frequently paired with this diagnosis based on PayerReady's Dx↔Px linkage data.
We don't have CPT pairings indexed for this specific code yet. Use the CPT search above to find common procedures, or check your payer's published medical policy for code-specific guidance.
Convert I51.4 to ICD-9-CM
Per CMS General Equivalence Mappings (GEMs), useful for legacy data review and historical claim analysis.
| ICD-10 | ICD-9 | Mapping Flags |
|---|---|---|
| I51.4 | 4290 | 00000 |
Flags format (5 digits): Approximate · No Map · Combination · Scenario · Choice List. Source: CMS 2017 GEMs (final version).
Codes Adjacent To I51.4
Other codes in section I30-I5A (Other forms of heart disease).
ICD-10 I51.4, Billing FAQ
Is ICD-10 code I51.4 billable? +
Yes, I51.4 is a billable ICD-10-CM code that can appear as a primary or secondary diagnosis on claims.
What other names or terms map to I51.4? +
ICD-10 I51.4 includes: Chronic (interstitial) myocarditis; Myocardial fibrosis; Myocarditis NOS.
What codes are Type 1 Excludes for I51.4? +
Type 1 Excludes (never code together with I51.4): acute or subacute myocarditis (I40.-)
Does I51.4 affect Medicare Advantage HCC risk adjustment? +
Yes. I51.4 maps to CMS-HCC v28 category 85. Capture this diagnosis annually for accurate Medicare Advantage risk score.
What ICD-9 codes does I51.4 map to? +
Per CMS GEMs, I51.4 maps to ICD-9 codes: 4290. Useful for legacy data review and historical claim analysis.
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Reviewed by the PayerReady Medical Coding Team
Verified against the CMS 2026 code set on May 31, 2026.
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