2026 ICD-10-CM Diagnosis Code I40.0Infective myocarditis
ICD-10-CM Codes›I00–I99›I30-I5A›I40
- Billable — Valid for Submission
- MCC — Major Complication or Comorbidity
- Not Chronic
I40.0 is a billable ICD-10-CM diagnosis code for infective myocarditis. It is valid on HIPAA claims for fiscal year 2026 (October 1, 2025 through September 30, 2026) and groups to MS-DRG 314 through 316, 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 22 closely related codes. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Myocarditis and cardiomyopathy.
Code Identity
Code Classification
Approximate SynonymsGuidance
Alternate terms and clinical phrases that map to this code.
- Abscess of myocardium
- Bacterial myocarditis
- Cardiovascular abnormality due to infective myocarditis
- Dilated cardiomyopathy due to bacterial myocarditis
- Dilated cardiomyopathy due to infectious disease
- Dilated cardiomyopathy due to parasitic myocarditis
- Enterovirus heart infection
- Fungal myocarditis
- Myocarditis caused by Aspergillus
- Myocarditis caused by Borrelia
- Myocarditis caused by Candida
- Myocarditis caused by echovirus
- Myocarditis caused by Rickettsia
- Myocarditis caused by Spirochaetales
- Myocarditis due to infectious agent
- Parasitic myocarditis
- Protozoan myocarditis
- Septic myocarditis - pneumococcal
- Septic myocarditis - staphylococcal
- Septic myocarditis - streptococcal
Tabular List NotesGuidance
Coding notes and annotation back-references applicable to this code.
Inclusion Terms
- Septic myocarditis
Use Additional Code
These terms are the conditions for which that code is to be used. The terms may be synonyms of the code title, or, in the case of "other specified" codes, the terms are a list of the various conditions assigned to that code. The inclusion terms are not necessarily exhaustive. Additional terms found only in the Alphabetic Index may also be assigned to a code.
The “use additional code” indicates that a secondary code could be used to further specify the patient’s condition. This note is not mandatory and is only used if enough information is available to assign an additional code.
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.
Clinical InformationClinical
Bacterial Myocarditis
myocarditis that is caused by an infection with a bacterial agent.
Patient EducationClinical
Cardiomyopathy
Cardiomyopathy is the name for diseases of the heart muscle. These diseases enlarge your heart muscle or make it thicker and more rigid than normal. In rare cases, scar tissue replaces the muscle tissue.
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Convert I40.0 to ICD-9-CMHistory
Code HistoryHistory
Questions About I40.0Overview
What is the ICD-10 code for infective myocarditis?
The ICD-10-CM code for infective myocarditis is I40.0 (sometimes written as I400). It is billable on HIPAA-covered claims from October 1, 2025 through September 30, 2026.
Is I40.0 (Acute myocarditis) a billable code?
Yes. This is a billable ICD-10-CM code, specific enough to report infective myocarditis on HIPAA-covered claims from October 1, 2025 through September 30, 2026.
What MS-DRG does I40.0 group to?
When infective myocarditis is the principal diagnosis on an inpatient stay, it groups to MS-DRG 314, 315, 316, 791, 793, 974, 975, 976, with relative weights from 0.6821 to 4.1696 depending on complications. Higher weights mean higher Medicare reimbursement.
Is I40.0 a CC or MCC?
CMS lists I40.0 as an MCC (major complication or comorbidity) for FY 2026. 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 22 closely related codes in its exclusion list.
What is the ICD-9 equivalent of I40.0?
Under the General Equivalence Mappings, infective myocarditis converts to ICD-9-CM 422.91 (idiopathic myocarditis) and 422.92 (septic myocarditis). The mapping is approximate, so confirm the match fits the documentation.
