2026 ICD-10-CM Diagnosis Code I33.0Acute and subacute infective endocarditis

ICD-10-CM Codes›I00–I99›I30-I5A›I33

ICD-10-CM I33.0
CMSSource: CMS FY 2026 ICD-10-CM dataset · Effective Oct 1, 2025 – Sep 30, 2026

I33.0 is a billable ICD-10-CM diagnosis code for acute and subacute infective endocarditis. It is valid on HIPAA claims for fiscal year 2026 (October 1, 2025 through September 30, 2026) and groups to MS-DRG 288 through 290, 974 through 976. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Endocarditis and endocardial disease.

Code Identity

ICD-10-CM Code
I33.0
Billable Status
Yes — Valid for Submission
Code Describes
Acute and subacute infective endocarditis
Short Description
Acute and subacute infective endocarditis
Same as the full description in the CMS dataset.
Parent Code
I33
Acute and subacute endocarditis

Code Classification

ChapterI00–I99Diseases of the circulatory system
SectionI30-I5AOther forms of heart disease
CategoryI33Acute and subacute endocarditis
This CodeI33.0Acute and subacute infective endocarditis

Approximate SynonymsGuidance

Alternate terms and clinical phrases that map to this code.

  • Abscess of tricuspid valve
  • Abscess of tricuspid valve caused by bacteria
  • Acute bacterial endocarditis
  • Acute endocarditis
  • Acute endocarditis co-occurrent with human immunodeficiency virus infection
  • Acute endocarditis of right side of heart due to infection
  • Acute endocarditis with AIDS
  • Acute infective endocarditis
  • Acute left sided infective endocarditis
  • Aortic valve vegetations
  • Arrhythmia due to vegetation of infective endocarditis
  • Bacterial endocarditis
  • Embolism due to infective heart valve vegetation
  • Endocarditis - blastomycosis
  • Endocarditis as complication of procedure
  • Endocarditis caused by Chlamydia
  • Endocarditis caused by Erysipelothrix rhusiopathiae
  • Endocarditis with infective aneurysm
  • Epilepsy due to bacterial endocarditis
  • Heart disease co-occurrent with human immunodeficiency virus infection
  • Infection by Blastomyces dermatitidis
  • Infection caused by Erysipelothrix rhusiopathiae
  • Infection causing myoendocarditis
  • Infection causing subacute endocarditis
  • Infectious vegetative endocarditis
  • Infective endocarditis
  • Infective endocarditis at site of implanted vascular shunt
  • Infective endocarditis at site of interatrial communication
  • Infective endocarditis at site of patch of interatrial communication
  • Infective endocarditis at site of patch of ventricular septal defect
  • Infective endocarditis at site of ventricular septal defect
  • Infective endocarditis of aortic valve
  • Infective endocarditis of cardiac valve
  • Infective endocarditis of cardiac valve with vegetation
  • Infective endocarditis of common atrioventricular valve
  • Infective endocarditis of heterograft
  • Infective endocarditis of homograft
  • Infective endocarditis of left atrioventricular valve
  • Infective endocarditis of left ventricular wall
  • Infective endocarditis of mitral valve
  • Infective endocarditis of pulmonary valve
  • Infective endocarditis of right atrioventricular valve
  • Infective endocarditis of right ventricular wall
  • Infective endocarditis of tricuspid valve
  • Infective endocarditis of truncal valve
  • Infective endocarditis of vascular cardiac conduit
  • Inflammation of aortic valve
  • Left sided infective endocarditis
  • Malignant endocarditis
  • Mitral valve vegetations
  • Mycotic aneurysm
  • Mycotic endocarditis
  • Named sign of foot
  • Osler's node
  • Osler's node of foot
  • Osler's node of hand
  • Prosthetic cardiac valve vegetation
  • Pulmonary valve vegetations
  • Purulent endocarditis
  • Rickettsial endocarditis
  • Right sided infective endocarditis
  • Right-sided Staphylococcus aureus endocarditis
  • Skin involvement in bacterial endocarditis
  • Staphylococcal endocarditis
  • Subacute bacterial endocarditis
  • Subacute endocarditis
  • Subacute endocarditis of left side of heart due to infection
  • Subacute endocarditis of right side of heart due to infection
  • Subacute endocarditis with AIDS
  • Thromboembolism due to vegetative endocarditis of heart valve
  • Tricuspid valve vegetations
  • Vegetation of heart
  • Vegetative endocarditis
  • Viral endocarditis

Tabular List NotesGuidance

Coding notes and annotation back-references applicable to this code.

Inclusion Terms

  • Bacterial endocarditis (acute) (subacute)
  • Infective endocarditis (acute) (subacute) NOS
  • Endocarditis lenta (acute) (subacute)
  • Malignant endocarditis (acute) (subacute)
  • Purulent endocarditis (acute) (subacute)
  • Septic endocarditis (acute) (subacute)
  • Ulcerative endocarditis (acute) (subacute)
  • Vegetative endocarditis (acute) (subacute)

Use Additional Code

Index to Diseases and InjuriesGuidance

Alphabetical index entries that point to this code.

External Cause of Injuries IndexGuidance

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

    • Aneurysm(anastomotic) (artery) (cirsoid) (diffuse) (false) (fusiform) (multiple) (saccular)
      • endocardial, infective (any valve)
    • Aneurysm(anastomotic) (artery) (cirsoid) (diffuse) (false) (fusiform) (multiple) (saccular)
      • infective
        • endocardial (any valve)
    • Aneurysm(anastomotic) (artery) (cirsoid) (diffuse) (false) (fusiform) (multiple) (saccular)
      • mycotic
        • endocardial (any valve)
    • Arthropathy
      • in (due to)
        • infective endocarditis
    • Arthropathy
      • reactive
        • in (due to)
          • infective endocarditis
    • Disorder(of)
      • glomerular (in)
        • subacute bacterial endocarditis
    • Endocarditis(chronic) (marantic) (nonbacterial) (thrombotic) (valvular)
      • acute or subacute
        • infective
    • Endocarditis(chronic) (marantic) (nonbacterial) (thrombotic) (valvular)
      • bacterial (acute) (any valve) (subacute)
    • Endocarditis(chronic) (marantic) (nonbacterial) (thrombotic) (valvular)
      • constrictive
    • Endocarditis(chronic) (marantic) (nonbacterial) (thrombotic) (valvular)
      • due to
        • Serratia marcescens
    • Endocarditis(chronic) (marantic) (nonbacterial) (thrombotic) (valvular)
      • infectious or infective (acute) (any valve) (subacute)
    • Endocarditis(chronic) (marantic) (nonbacterial) (thrombotic) (valvular)
      • lenta (acute) (any valve) (subacute)
    • Endocarditis(chronic) (marantic) (nonbacterial) (thrombotic) (valvular)
      • malignant (acute) (any valve) (subacute)
    • Endocarditis(chronic) (marantic) (nonbacterial) (thrombotic) (valvular)
      • mitral (chronic) (double) (fibroid) (heart) (inactive) (valve) (with chorea)
        • active or acute
          • bacterial
    • Endocarditis(chronic) (marantic) (nonbacterial) (thrombotic) (valvular)
      • mycotic (acute) (any valve) (subacute)
    • Endocarditis(chronic) (marantic) (nonbacterial) (thrombotic) (valvular)
      • pneumococcal (acute) (any valve) (subacute)
    • Endocarditis(chronic) (marantic) (nonbacterial) (thrombotic) (valvular)
      • purulent (acute) (any valve) (subacute)
    • Endocarditis(chronic) (marantic) (nonbacterial) (thrombotic) (valvular)
      • septic (acute) (any valve) (subacute)
    • Endocarditis(chronic) (marantic) (nonbacterial) (thrombotic) (valvular)
      • streptococcal (acute) (any valve) (subacute)
    • Endocarditis(chronic) (marantic) (nonbacterial) (thrombotic) (valvular)
      • suppurative (acute) (any valve) (subacute)
    • Endocarditis(chronic) (marantic) (nonbacterial) (thrombotic) (valvular)
      • ulcerative (acute) (any valve) (subacute)
    • Endocarditis(chronic) (marantic) (nonbacterial) (thrombotic) (valvular)
      • vegetative (acute) (any valve) (subacute)
    • Glomerulonephritis
      • in (due to)
        • subacute bacterial endocarditis
    • Infection, infected, infective(opportunistic)
      • endocardium
    • Nephritis, nephritic(albuminuric) (azotemic) (congenital) (disseminated) (epithelial) (familial) (focal) (granulomatous) (hemorrhagic) (infantile) (nonsuppurative, excretory) (uremic)
      • due to
        • subacute bacterial endocarditis
    • Node(s)
      • Osler's
    • Osler's nodes
    • SBE(subacute bacterial endocarditis)
    • Ulcer, ulcerated, ulcerating, ulceration, ulcerative
      • valve, heart
    • Vegetation, vegetative
      • endocarditis (acute) (any valve) (subacute)
    • Vegetation, vegetative
      • heart (mycotic) (valve)

Clinical ClassificationClinical

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

CCSR CIR004
Endocarditis and endocardial disease
Default principal diagnosis: inpatient Yes · outpatient Yes

Clinical InformationClinical

  • Mycotic Aneurysm

    an aneurysm caused by an infection.

  • Bacterial Endocarditis

    endocarditis that is caused by an infection with a bacterial agent.

  • Subacute Bacterial Endocarditis|SBE

    subacute inflammation of the endocardium. streptococcus viridans is the usual etiologic agent of subacute bacterial endocarditis. the distinction between "acute" and "subacute" endocarditis has traditionally been made based on the pathogenic organism and clinical presentation.

  • Acute and Subacute Endocarditis, Unspecified|Acute and subacute endocarditis, unspecified

    evidence of acute and subacute endocarditis.

  • Acute Endocarditis

    acute inflammation of the endocardium. bacteria is the usual etiologic agent, and the distinction between "acute" and "subacute" has traditionally been made based on the pathogenic organism and clinical presentation.

Patient EducationClinical

Endocarditis

Endocarditis is sometimes called infective endocarditis. It's a rare but life-threatening inflammation of the lining inside your heart's chambers and valves (the endocardium).

The full article covers:

  • What is endocarditis?
  • What causes endocarditis?
  • Who is more likely to develop endocarditis?
  • What are the symptoms of endocarditis?
  • What other problems can endocarditis cause?
  • How is endocarditis diagnosed?
  • What are the treatments for endocarditis?
  • Can endocarditis be prevented?

Read the full article at MedlinePlus

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

Convert I33.0 to ICD-9-CMHistory

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

ICD-9-CM
421.0 Ac/subac bact endocard
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 I33.0Overview

Is I33.0 (Acute and subacute endocarditis) a billable code?

Yes. This is a billable ICD-10-CM code, specific enough to report acute and subacute infective endocarditis on HIPAA-covered claims from October 1, 2025 through September 30, 2026.

What MS-DRG does I33.0 group to?

When acute and subacute infective endocarditis is the principal diagnosis on an inpatient stay, it groups to MS-DRG 288, 289, 290, 974, 975, 976, with relative weights from 0.8945 to 2.8860 depending on complications. Higher weights mean higher Medicare reimbursement.

What is the ICD-9 equivalent of I33.0?

Under the General Equivalence Mappings, acute and subacute infective endocarditis converts to ICD-9-CM 421.0 (ac/subac bact endocard). 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.