ICD-10 I42.9
Billable / Specific HCC v28: 85 CCCardiomyopathy, unspecified
About ICD-10-CM I42.9
ICD-10-CM code I42.9 represents Cardiomyopathy, unspecified. This is a billable/specific code in the Circulatory System chapter (block I42). The 2026 edition of ICD-10-CM I42.9 became effective on October 1, 2025.
Coding Tips for I42.9
Specialist guidance from the PayerReady Medical Coding Team. Specificity warnings, HCC capture rules, sequencing notes.
I42.9 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.
I42.9 is designated CC for MS-DRG grouping. On inpatient claims, this code can shift the DRG to the with-CC variant when documented as a present-on-admission secondary diagnosis. Hospital CDI programs flag CC opportunities during chart review. Failure to capture this code may leave 30 to 80 percent of the inpatient stay revenue unrealized.
Inclusion Terms / Approximate Synonyms
Clinical terms and conditions classified under I42.9. Per CMS ICD-10-CM Tabular 2026.
- Cardiomyopathy (primary) (secondary) NOS
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.
Inpatient DRG Impact, CC
codes Cardiomyopathy, unspecified. As a Complication/Comorbidity (CC), this contributes to DRG severity adjustment when documented alongside the principal diagnosis.
Medicare LCD Coverage for I42.9
Local Coverage Determinations (LCDs) from CMS MACs that list I42.9 as a covered diagnosis.
Showing top 10 of 347 total . Click a CPT for full coverage scope.
Commercial Payer Coverage
Coverage policies from major commercial payers referencing I42.9.
1 Aetna
3 Cigna
5 Medicare
CPT Codes Commonly Billed with I42.9
Procedures frequently paired with this diagnosis based on PayerReady's Dx↔Px linkage data.
- 93306 Echocardiography — heart failure, cardiomyopathy, valvular disease Cardiovascular Disease
- 93000 EKG 12-lead — tachycardia, bradycardia, palpitations, HTN, CAD, AFib, arrhythmia, chest pain, syncope, cardiomyopathy, AV block, bundle branch block, SVT, VT, diabetes screening, abnormal EKG Cardiology
- 93306 Echo with Doppler — heart failure, cardiomyopathy, mitral/aortic/tricuspid valve disease, chest pain, dyspnea, CAD, pulmonary HTN, ASD, VSD, congenital valve Cardiology
- 93350 Stress echo — known/suspected CAD, chest pain, angina, abnormal EKG, cardiomyopathy, HF, dyspnea Cardiology
- 0077U CMS LCD: Billing and Coding: Mass Spectrometry (MS) Testing in Monoclonal Gammopathy (MG) CMS LCD
Convert I42.9 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 |
|---|---|---|
| I42.9 | 4254 | 10000 |
| I42.9 | 4259 | 10000 |
Flags format (5 digits): Approximate · No Map · Combination · Scenario · Choice List. Source: CMS 2017 GEMs (final version).
Codes Adjacent To I42.9
Other codes in section I30-I5A (Other forms of heart disease).
ICD-10 I42.9, Billing FAQ
Is ICD-10 code I42.9 billable? +
Yes, I42.9 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 I42.9? +
ICD-10 I42.9 includes: Cardiomyopathy (primary) (secondary) NOS.
Does I42.9 affect Medicare Advantage HCC risk adjustment? +
Yes. I42.9 maps to CMS-HCC v28 category 85. Capture this diagnosis annually for accurate Medicare Advantage risk score.
Is I42.9 a CC or MCC for inpatient DRG? +
Yes, this code is designated as CC. Documenting as a secondary diagnosis on inpatient claims can shift the DRG to a higher-weighted category.
What CPT codes are commonly billed with I42.9? +
Procedures frequently paired with I42.9 include: 93306, 93000, 93306, 93350, 0077U.
What ICD-9 codes does I42.9 map to? +
Per CMS GEMs, I42.9 maps to ICD-9 codes: 4254, 4259. 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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