2027 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 2027 ICD-10-CM dataset · Effective Oct 1, 2026 – Sep 30, 2027

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 2027 (October 1, 2026 through September 30, 2027) and groups to MS-DRG 288 through 290, 791, 793, 974 through 976. As a secondary diagnosis, it counts as a major complication or comorbidity (MCC) and places an inpatient stay in the highest severity level of its MS-DRG family. It does not count, however, when the principal diagnosis is one of 15 closely related codes. 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 caused by Streptococcus suis
  • 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 caused by Streptococcus suis
  • 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

Instructional NotesGuidance

Instructions from the official ICD-10-CM Tabular List that apply to I33.0: its own notes plus those printed at I33 and Chapter 9. A note printed at a category, block or chapter applies to every code under it.

Applicable To

Conditions this code is used for: synonyms of the title or, for "other specified" codes, the conditions assigned to it. The list is not exhaustive.

  • 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)

Excludes1

Not coded here: the excluded code is never reported together with this one, unless the two conditions are unrelated.

From I33 Acute and subacute endocarditis applies to 2 codes
  • acute rheumatic endocarditis (I01.1)
  • endocarditis NOS (I38)

Excludes2

Not included here: the excluded condition is not part of this code, but a patient may have both, so both codes may be reported.

From Chapter 9 (I00-I99) Diseases of the circulatory system applies to 1,433 codes
  • certain conditions originating in the perinatal period (P04-P96)
  • certain infectious and parasitic diseases (A00-B99)
  • complications of pregnancy, childbirth and the puerperium (O00-O9A)
  • congenital malformations, deformations, and chromosomal abnormalities (Q00-Q99)
  • endocrine, nutritional and metabolic diseases (E00-E88)
  • injury, poisoning and certain other consequences of external causes (S00-T88)
  • neoplasms (C00-D49)
  • symptoms, signs and abnormal clinical and laboratory findings, not elsewhere classified (R00-R94)
  • systemic connective tissue disorders (M30-M36)
  • transient cerebral ischemic attacks and related syndromes (G45.-)

Use Additional Code

Add a second code, after this one, to fully describe the condition.

  • code (B95-B97) to identify infectious agent

Source: CMS ICD-10-CM Tabular List. How to read instructional notes.

Referenced in Other NotesGuidance

Instructional notes printed at other codes that name I33.0, its category, or a range that includes it.

Code First 2

These codes say to code first a condition named in the note, and I33.0 is one of the conditions named.

  • I76 Septic arterial embolism
    infective endocarditis (I33.0)
  • M02 Postinfective and reactive arthropathies
    infective endocarditis (I33.0)

Index to Diseases and InjuriesGuidance

Alphabetical index entries that point to this code.

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

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 2017–2026No changes
FY 2027CurrentCurrent code set, no changesEffective October 1, 2026 through September 30, 2027.

Questions About I33.0Overview

What is the ICD-10 code for acute and subacute infective endocarditis?

The ICD-10-CM code for acute and subacute infective endocarditis is I33.0 (sometimes written as I330). It is billable on HIPAA-covered claims from October 1, 2026 through September 30, 2027.

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, 2026 through September 30, 2027.

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 793, 289, 791, 974, 976, 975, 288, 290, with relative weights from 0.7843 to 4.2192 depending on complications. Higher weights mean higher Medicare reimbursement.

Is I33.0 a CC or MCC?

CMS lists I33.0 as an MCC (major complication or comorbidity) for FY 2027. Reported as a secondary diagnosis, it places the inpatient stay in the highest-weighted DRG of its severity family. It does not count when the principal diagnosis is one of the 15 closely related codes in its exclusion list.

Can I33.0 be reported with I01.1?

Not as a rule. The Excludes1 note at I33, which applies to I33.0, lists "acute rheumatic endocarditis (I01.1)". An Excludes1 note means the excluded code is never reported together with this one; the only exception is when the two conditions are unrelated to each other (Official Guidelines, Section I.A.12.a).