2026 ICD-10-CM Diagnosis Code A36.81Diphtheritic cardiomyopathy

ICD-10-CM Codes›A00–B99›A30-A49›A36

ICD-10-CM A36.81
CMSSource: CMS FY 2026 ICD-10-CM dataset · Effective Oct 1, 2025 – Sep 30, 2026

A36.81 is a billable ICD-10-CM diagnosis code for diphtheritic cardiomyopathy. 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. Coders also document this condition as acute myocarditis. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Bacterial infections and Myocarditis and cardiomyopathy.

Code Identity

ICD-10-CM Code
A36.81
Billable Status
Yes — Valid for Submission
Code Describes
Diphtheritic cardiomyopathy
Short Description
Diphtheritic cardiomyopathy
Same as the full description in the CMS dataset.
Parent Code
A36.8
Other diphtheria

Code Classification

ChapterA00–B99Certain infectious and parasitic diseases
SectionA30-A49Other bacterial diseases
CategoryA36Diphtheria
This CodeA36.81Diphtheritic cardiomyopathy

Approximate SynonymsGuidance

Alternate terms and clinical phrases that map to this code.

  • Acute myocarditis
  • Acute myocarditis - diphtheritic
  • Cardiomyopathy due to diphtheria
  • Diphtheritic myocarditis

Tabular List NotesGuidance

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

Inclusion Terms

  • Diphtheritic myocarditis

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.

    • Diphtheria, diphtheritic(gangrenous) (hemorrhagic)
      • myocarditis
    • Myocarditis(with arteriosclerosis)(chronic)(fibroid) (interstitial) (old) (progressive) (senile)
      • diphtheritic
    • Myocarditis(with arteriosclerosis)(chronic)(fibroid) (interstitial) (old) (progressive) (senile)
      • in (due to)
        • diphtheria

Clinical ClassificationClinical

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

CCSR INF003
Bacterial infections
Default principal diagnosis: inpatient No · outpatient No
CCSR CIR005
Myocarditis and cardiomyopathy
Default principal diagnosis: inpatient Yes · outpatient Yes

Clinical InformationClinical

  • Acute Myocarditis

    the sudden onset of inflammation of heart muscle with myocellular necrosis; this is generally secondary to an infectious cause, and patients often have a recent history of a flu-like illness.

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.

Read the full article at MedlinePlus

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

Convert A36.81 to ICD-9-CMHistory

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

ICD-9-CM
032.82 Diphtheritic myocarditis
Exact Match The mapping is direct, with no qualifiers.

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 A36.81Overview

Is A36.81 (Other diphtheria) a billable code?

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

What MS-DRG does A36.81 group to?

When diphtheritic cardiomyopathy is the principal diagnosis on an inpatient stay, it groups to MS-DRG 314, 315, 316, with relative weights from 0.6821 to 2.0852 depending on complications. Higher weights mean higher Medicare reimbursement.

What is the ICD-9 equivalent of A36.81?

Under the General Equivalence Mappings, diphtheritic cardiomyopathy converts to ICD-9-CM 032.82 (diphtheritic myocarditis). The mapping is a direct match.

Footnotes

[1] Not chronic - A diagnosis code that does not fit the criteria for chronic condition (duration, ongoing medical treatment, and limitations) is considered not chronic. Some codes designated as not chronic are acute conditions. Other diagnosis codes that indicate a possible chronic condition, but for which the duration of the illness is not specified in the code description (i.e., we do not know the condition has lasted 12 months or longer) also are considered not chronic.