I42.09 ICD-10-CM Code: Other dilated cardiomyopathy

Coding instructions

Official Tabular Instructional Notes: the inclusion, exclusion and sequencing notes published for I42.09 in the official ICD-10-CM tabular list, quoted as published.

Source: CMS/CDC — ICD-10-CM Tabular ListRelease: FY2026Effective: October 1, 2025

Notes without a marker are published on I42.09 itself; “inherited from” names the category or block whose note applies here.

Coder workflow for I42.09

MedCoder structured workflow — derived from this code’s own official record

Before you code I42.09

1. “Other” (NEC) means the condition is specified in the record but no dedicated code captures it. Confirm the documented form is not one a sibling code names before settling on I42.09; if the record states no specifics at all, the unspecified sibling applies instead. “Other” codes are for documented conditions the classification gives no specific code; “unspecified” codes are for records lacking the detail (Guidelines I.A.9.a, I.A.9.b).

   ReviewI42.01

   See the relationships section · Guide: Other vs unspecified (NEC vs NOS) →

Choose the right path

1. Is the underlying (etiologic) condition the Code First note names documented?
   Yes → Sequence the underlying condition first, then I42.09.
   No → Continue; do not add an underlying condition the record does not document.

   ReviewO99.4

Consider I42.09. Then confirm the code is valid for the date of service in the Verify section.

Documentation check

The provider’s diagnostic statement

Codes are assigned from the provider’s documented diagnosis, not from clinical criteria, test values or a medication list (Guidelines I.A.19).

The underlying (etiologic) condition

Named in the Code First note; sequenced before this code when documented (Guidelines I.A.13).

Any detail beyond this code’s title

What the record states that a more specific sibling code would capture — or its absence, which itself supports the unspecified code.

Official instructions as workflow

• Excludes2 — not part of I42.09(3 notes)

  Coding workflow: The conditions named in this note are not included in I42.09. When the record documents both, both may be reported; the note is a boundary, not a prohibition.

  CompareI25.5, O90.3, I51.7

  See the official tabular notes · Guidelines I.A.12.b

• Code First — sequencing check(1 note)

  Coding workflow: Check whether the underlying or etiologic condition the note names is documented. When it is, sequence it before I42.09. Do not add an underlying condition the record does not document.

  ReviewO99.4

  See the official tabular notes · Guidelines I.A.13

Coding decision scenarios

Pattern scenarios for this code’s structure — decision rules, not clinical cases

Every row is derived from this code’s own record — its title, tabular notes, 7th-character family and same-category siblings — with fixed MedCoder wording; nothing is inferred about a patient. The official notes and guideline text are in the sections each row links to, and they control.

Indexed Clinical Terms (1)

Official source data — entries quoted as published, in the Index’s own lookup phrasing

Clinical term phrases from the official ICD-10-CM Index to Diseases and Injuries that map to this code. These are alphabetic-index entries shown as the Index writes them — lookup phrasing, not necessarily the wording of a final diagnosis.

• Cardiomyopathy (familial) (idiopathic), dilated, specified NEC (nonfamilial)

Don’t confuse I42.09 with…

MedCoder analysis — pairs from this code’s official notes, distinctions written by MedCoder

The codes most likely to be picked instead of I42.09 — named in its own official notes, or sharing its laterality or encounter family — with what separates them and which documentation moves the case. Each links to the full comparison.

• I42.00— Specificity relationship (Review)

  Overlapping diagnoses in the same category.

  Overlapping codes in the same category — the documentation decides which is the more specific fit.

  What moves you there: A record that documents no more than “Dilated cardiomyopathy, unspecified” takes I42.00; specificity in the record moves it back here.

  Full comparison: I42.09 vs I42.00 →

• I25.5— Excludes2 relationship (Informational)

  Distinct conditions — both may be reported.

  A distinct condition — both may be reported when both are documented.

  What moves you there: Documentation of ischemic cardiomyopathy adds I25.5; it is not part of this code and both may be reported when both are documented.

  Full comparison: I42.09 vs I25.5 →

• O90.3— Excludes2 relationship (Informational)

  Distinct conditions — both may be reported.

  A distinct condition — both may be reported when both are documented.

  What moves you there: Documentation of peripartum cardiomyopathy adds O90.3; it is not part of this code and both may be reported when both are documented.

  Full comparison: I42.09 vs O90.3 →

• I51.7— Excludes2 relationship (Informational)

  Distinct conditions — both may be reported.

  A distinct condition — both may be reported when both are documented.

  What moves you there: Documentation of ventricular hypertrophy adds I51.7; it is not part of this code and both may be reported when both are documented.

  Full comparison: I42.09 vs I51.7 →

Relationships are read from this code's own official notes, its laterality siblings and its encounter family; the wording of each distinction is MedCoder editorial, and the documentation named in each “what moves you there” line is the official note phrase or sibling title itself. Source: CMS ICD-10-CM tabular instructional notes; ICD-10-CM Official Guidelines, Section I.A.12.a.

Verify Before Coding

• No Medicare Code Editor or MS-DRG Definitions Manual restrictions apply to this code.

From the code registry, the Medicare Code Editor, and the MS-DRG Definitions Manual. Check it against a full claim in Claim Check.

Relationships & Classification

MedCoder structured relationships — computed from published CMS and AHRQ datasets

Other codes that name I42.09 or its code family, from the CMS ICD-10-CM tabular instructional notes. Tabular-note edges are stored at the code family level that carries each note.

Referenced by 1 Code First instruction: I5A — Non-ischemic myocardial injury (non-traumatic) (via I42.-).

Each of these codes carries a Code First note naming this condition — when that code is reported, THIS code is sequenced first, ahead of it.

Referenced by 1 Code Also instruction: E74.05 — Lysosome-associated membrane protein 2 [LAMP2] deficiency (via I42.0.-).

These codes suggest coding this condition alongside when both are present.

Related Codes

Same Index main term, other category

The ICD-10-CM Index to Diseases and Injuries files this code under the main term “Cardiomyopathy”; these codes share that main term but sit in a different category of the Tabular List.

A18.84 — Tuberculosis of heart (tuberculous), B33.24 — Viral cardiomyopathy (viral), B57.0 — Acute Chagas' disease with heart involvement (in, Chagas' disease, acute), B57.2 — Chagas' disease (chronic) with heart involvement (in, Chagas' disease), D86.85 — Sarcoid myocarditis (in, sarcoidosis), E05.90 — Thyrotoxicosis, unspecified without thyrotoxic crisis or storm (thyrotoxic), E05.91 — Thyrotoxicosis, unspecified with thyrotoxic crisis or storm (thyrotoxic, with thyroid storm), E51.12 — Wet beriberi (beriberi), E63.9 — Nutritional deficiency, unspecified (nutritional), E74.02 — Pompe disease (glycogen storage), E85.4 — Organ-limited amyloidosis (amyloid), E88.9 — Metabolic disorder, unspecified (metabolic), G11.11 — Friedreich ataxia (due to, Friedreich's ataxia), G71.09 — Other specified muscular dystrophies (due to, progressive muscular dystrophy), G71.11 — Myotonic muscular dystrophy (due to, myotonia atrophica), I09.0 — Rheumatic myocarditis (rheumatic), I25.5 — Ischemic cardiomyopathy (ischemic), I51.81 — Takotsubo syndrome (takotsubo), O90.3 — Peripartum cardiomyopathy (postpartum), Q24.8 — Other specified congenital malformations of heart (hypertrophic, obstructive, congenital)

Contextual Map

Every relationship of I42.09 in one view: hierarchy, official tabular instructions in both directions, clinical classification, risk adjustment, MS-DRG participation, index terms and change history — each edge carrying the CMS source it derives from.

Run I42.09 with these 2 related codes in Claim Check

Hierarchy

• I00-I99 — Chapter 9: Diseases of the Circulatory System (I00-I99) (I00-I99)[Hierarchy]— CMS ICD-10-CM tabular structure · icd10cm-fy2026
• I30-I5A — Other forms of heart disease[Hierarchy]— CMS ICD-10-CM tabular structure · icd10cm-fy2026

Referenced by Code First instructions

• I5A — Non-ischemic myocardial injury (non-traumatic)[Code First](via I42.-): “cardiomyopathy (I42.-)”— CMS ICD-10-CM tabular instructional notes · icd10cm-fy2026

Referenced by Code Also instructions

• E74.05 — Lysosome-associated membrane protein 2 [LAMP2] deficiency[Code Also](via I42.0.-): “dilated cardiomyopathy (I42.0-)”— CMS ICD-10-CM tabular instructional notes · icd10cm-fy2026

Index entries

• Cardiomyopathy (familial) (idiopathic), dilated, specified NEC (nonfamilial)[Index term]— CMS ICD-10-CM Index to Diseases and Injuries · icd10cm-fy2026

Nearest codes (15)

• I42 — Cardiomyopathy[Sibling]— CMS ICD-10-CM tabular structure · icd10cm-fy2026
• I42.0 — Dilated cardiomyopathy[Sibling]— CMS ICD-10-CM tabular structure · icd10cm-fy2026
• I42.00 — Dilated cardiomyopathy, unspecified[Sibling]— CMS ICD-10-CM tabular structure · icd10cm-fy2026
• I42.01 — Familial-genetic dilated cardiomyopathy[Sibling]— CMS ICD-10-CM tabular structure · icd10cm-fy2026
• I42.1 — Obstructive hypertrophic cardiomyopathy[Sibling]— CMS ICD-10-CM tabular structure · icd10cm-fy2026
• I42.2 — Other hypertrophic cardiomyopathy[Sibling]— CMS ICD-10-CM tabular structure · icd10cm-fy2026
• I42.3 — Endomyocardial (eosinophilic) disease[Sibling]— CMS ICD-10-CM tabular structure · icd10cm-fy2026
• I42.4 — Endocardial fibroelastosis[Sibling]— CMS ICD-10-CM tabular structure · icd10cm-fy2026
• and 7 more

Change history

• FY2027 — Will be added to the code set[Change history]— CMS release files (code change ledger) · icd10cm-fy2027

Sources for this page

Codes, titles, notes, index terms and mappings on this page are transcribed from the datasets below. Relationships MedCoder computed and text MedCoder wrote are labelled where they appear.

Code, title, tabular notes and index terms Official source data

CMS/CDC ICD-10-CM FY2026 tabular list, index and tables, effective October 1, 2025 Release, file and checksum · Publisher’s page

Claim edits Official source data

CMS Definitions of Medicare Code Edits — v43.1 (April 2026) Release, file and checksum · Publisher’s page

Change history and date-of-service validity Official source data

CMS ICD-10-CM release addenda, ingested release by release into the change ledger Release, file and checksum · Publisher’s page

Comparisons, relationships and the contextual map MedCoder structured relationship

Computed by MedCoder from the tabular notes and tables above; every derived relationship is marked as derived where it appears

Summary and FAQ answers MedCoder explanation

Written by MedCoder to explain the sources above: drafted with AI assistance, checked by a person against the release files, and labelled as MedCoder text where it appears. Not official text.

Labels on this page: Official source data · MedCoder structured relationship · MedCoder explanation. How to read the labels · All data sources and release dates

Nearest Codes in This Family

Official ICD-10-CM classifications closest to I42.09 in its code family, with their registry titles.

• I42 — Cardiomyopathy
• I42.0 — Dilated cardiomyopathy
• I42.00 — Dilated cardiomyopathy, unspecified
• I42.01 — Familial-genetic dilated cardiomyopathy
• I42.1 — Obstructive hypertrophic cardiomyopathy
• I42.2 — Other hypertrophic cardiomyopathy
• I42.3 — Endomyocardial (eosinophilic) disease
• I42.4 — Endocardial fibroelastosis
• I42.5 — Other restrictive cardiomyopathy
• I42.6 — Alcoholic cardiomyopathy

View all codes in the I42 family