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ICD-10-CM 2027 diagnosis code

I09.1Rheumatic diseases of endocardium, valve unspecified

✓ Billable / specific

I09.1 is a valid, billable ICD-10-CM code for rheumatic diseases of endocardium, valve unspecified. It can be reported on claims for dates of service from October 1, 2026 – September 30, 2027.

Looking up by condition? See ICD-10 code for Rheumatic endocarditis.

Code unchanged since ICD-10-CM took effect on October 1, 2015. Source: official FY2027 ICD-10-CM release from CDC/NCHS and CMS. Page updated September 29, 2026. About our data

About I09.1

I09.1 is the ICD-10-CM diagnosis code for rheumatic diseases of endocardium, valve unspecified. It belongs to category I09 (other rheumatic heart diseases), block I05-I09 (chronic rheumatic heart diseases) and chapter 9 (diseases of the circulatory system). It is billable, so it can be reported on its own for dates of service from October 1, 2026 through September 30, 2027.

Within I09, choose I09.1 (Rheumatic diseases of endocardium, valve unspecified) only when documentation doesn't support a more specific option: rheumatic myocarditis (I09.0), chronic rheumatic pericarditis (I09.2), other specified rheumatic heart diseases (I09.8) and rheumatic heart disease, unspecified (I09.9).

Don't report I09.1 together with the conditions in its Excludes1 note: endocarditis, valve unspecified (I38).

It is not a CC or MCC, so as a secondary diagnosis it doesn't change the MS-DRG severity level.

In MS-DRG v44.0, it is part of the grouping logic for DRG 306 (Cardiac Congenital and Valvular Disorders with MCC, relative weight 1.546) and DRG 307 (Cardiac Congenital and Valvular Disorders without MCC, relative weight 0.9148), in MDC 05 (Diseases and Disorders of the Circulatory System), as a principal or secondary diagnosis. The DRG a claim lands in depends on the principal diagnosis, procedures and any CC/MCC secondary diagnoses.

It has been part of ICD-10-CM since the code set took effect on October 1, 2015 and hasn't changed since.

Before ICD-10, this condition was coded in ICD-9-CM as 397.9 (rheumatic diseases of endocardium, valve unspecified).

Coding notes

Applicable toConditions and synonyms classified to this code
  • Rheumatic endocarditis (chronic)
  • Rheumatic valvulitis (chronic)
Excludes1Not coded here — never report together with this code
  • endocarditis, valve unspecified (I38)

Notes that apply from higher levels

Instructions written at a parent level also apply to I09.1.

Broader instructions also apply from Chapter 9: Diseases of the circulatory system.

Alphabetic index entries

3 entries

Terms in the official ICD-10-CM index that lead to I09.1.

Codes whose notes reference I09.1

MS-DRG v44.0 grouping

All DRGs →

Inpatient MS-DRGs this diagnosis can group to, as the principal or a secondary diagnosis, depending on the rest of the claim.

ICD-9-CM equivalent

Converter →
  • 397.9Rheumatic diseases of endocardium, valve unspecifiedapproximate

From the CMS 2018 General Equivalence Mappings (GEMs), the final GEMs release.

Code history

  1. 2016
  2. 2017
  3. 2018
  4. 2019
  5. 2020
  6. 2021
  7. 2022
  8. 2023
  9. 2024
  10. 2025
  11. 2026
  12. 2027
  • FY2016 (effective 10/1/2015): Added (first year of ICD-10-CM)
  • No changes since FY2016.

Common questions about I09.1

Is I09.1 billable?

Yes. I09.1 is a billable/specific ICD-10-CM code valid for FY2027 (October 1, 2026 – September 30, 2027).

Can I09.1 be used as a principal diagnosis?

Yes. The Medicare Code Editor doesn't restrict I09.1 as a principal diagnosis.

Is I09.1 a CC or MCC?

No. I09.1 is neither a CC nor an MCC under MS-DRG v44.0.

What DRG does I09.1 group to?

I09.1 is used in the MS-DRG v44.0 logic for MS-DRG 306 (Cardiac Congenital and Valvular Disorders with MCC) and MS-DRG 307 (Cardiac Congenital and Valvular Disorders without MCC). Which one applies depends on whether it is the principal diagnosis and on the rest of the claim.

What is the ICD-9 code for I09.1?

The CMS General Equivalence Mappings map I09.1 to ICD-9-CM 397.9.