2026 ICD-10-CM Diagnosis Code I51.9Heart disease, unspecified

ICD-10-CM Codes›I00–I99›I30-I5A›I51

ICD-10-CM I51.9
CMSSource: CMS FY 2026 ICD-10-CM dataset · Effective Oct 1, 2025 – Sep 30, 2026

I51.9 is a billable ICD-10-CM diagnosis code for heart disease, unspecified. It is valid on HIPAA claims for fiscal year 2026 (October 1, 2025 through September 30, 2026) and groups to MS-DRG 302 through 303. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Other and ill-defined heart disease.

Code Identity

ICD-10-CM Code
I51.9
Billable Status
Yes — Valid for Submission
Code Describes
Heart disease, unspecified
Short Description
Heart disease, unspecified
Same as the full description in the CMS dataset.
Parent Code
I51
Complications and ill-defined descriptions of heart disease

Code Classification

ChapterI00–I99Diseases of the circulatory system
SectionI30-I5AOther forms of heart disease
CategoryI51Complications and ill-defined descriptions of heart disease
This CodeI51.9Heart disease, unspecified

Approximate SynonymsGuidance

Alternate terms and clinical phrases that map to this code.

  • Acute heart disease
  • Cachexia
  • Cardiac cachexia
  • Cardiac cirrhosis
  • Cardiac complication
  • Cardiac disease in pregnancy
  • Cardiac disease treatment started
  • Cardiac portal cirrhosis
  • Cardiac treatment changed
  • Cardiac: dubious diagnostic criteria
  • Chronic heart disease
  • Disorder of left atrium as complication of procedure
  • Disorder of right cardiac ventricle
  • Distribution of body fat loss - finding
  • Heart disease
  • Heart disease caused by ionizing radiation
  • Heart disease co-occurrent with human immunodeficiency virus infection
  • Heart disease in mother complicating childbirth
  • Heart disease in mother complicating pregnancy, childbirth AND/OR puerperium
  • Hepatic congestion
  • Hypogonadism with anosmia
  • Hypogonadotropic hypogonadism due to isolated gonadotropin deficiency
  • Kallman syndrome with heart disease
  • Loss of sense of smell
  • Myocardial lesion

Index to Diseases and InjuriesGuidance

Alphabetical index entries that point to this code.

  • - Morbus - See Also: Disease;

    • - cordis - See Also: Disease, heart; - I51.9

External Cause of Injuries IndexGuidance

References for this code in the External Cause of Injuries Index.

    • Cardiopathy
    • Complication(s) (from) (of)
      • heart
    • Disease, diseased
      • heart (organic)
    • Disease, diseased
      • heart (organic)
        • cryptogenic
    • Dysfunction
      • ventricular
    • Lesion(s) (nontraumatic)
      • cardiac
    • Morbus
      • cordis

Clinical ClassificationClinical

AHRQ’s CCSR groups this code into broader clinical categories.

CCSR CIR015
Other and ill-defined heart disease
Default principal diagnosis: inpatient Yes · outpatient Yes

Clinical InformationClinical

  • Cachexia

    general ill health, malnutrition, and weight loss, usually associated with chronic disease.

Patient EducationClinical

Heart Diseases

Heart disease is a general term that includes many types of heart problems. It's a type of cardiovascular disease, which means heart and blood vessel disease.

The full article covers:

  • What is heart disease?
  • What are the types of heart disease?
  • What causes heart diseases?
  • Who is more likely to develop heart diseases?
  • What are the symptoms of heart disease?
  • How are heart diseases diagnosed?
  • What are the treatments for heart disease?
  • Can heart diseases be prevented?

Read the full article at MedlinePlus

Courtesy of MedlinePlus, a service of the U.S. National Library of Medicine.

Convert I51.9 to ICD-9-CMHistory

The closest ICD-9-CM equivalents under the General Equivalence Mappings.

ICD-9-CM
429.9 Heart disease NOS
Approximate The match is approximate rather than exact.

Code HistoryHistory

FY 2016AddedAdded to the ICD-10-CM code setEffective October 1, 2015, the first year of ICD-10-CM.
FY 2017–2025No changes
FY 2026CurrentCurrent code set, no changesEffective October 1, 2025 through September 30, 2026.

Questions About I51.9Overview

Is I51.9 (Complications and ill-defined descriptions of heart disease) a billable code?

Yes. This is a billable ICD-10-CM code, specific enough to report heart disease, unspecified on HIPAA-covered claims from October 1, 2025 through September 30, 2026.

What MS-DRG does I51.9 group to?

When heart disease, unspecified is the principal diagnosis on an inpatient stay, it groups to MS-DRG 302, 303, with relative weights from 0.6732 to 1.1966 depending on complications. Higher weights mean higher Medicare reimbursement.

What is the ICD-9 equivalent of I51.9?

Under the General Equivalence Mappings, heart disease, unspecified converts to ICD-9-CM 429.9 (heart disease NOS). The mapping is approximate, so confirm the match fits the documentation.

Footnotes

[1] Chronic - a chronic condition code indicates a condition lasting 12 months or longer and its effect on the patient based on one or both of the following criteria:

  • The condition results in the need for ongoing intervention with medical products,treatment, services, and special equipment
  • The condition places limitations on self-care, independent living, and social interactions.