2026 ICD-10-CM Diagnosis Code A36.81Diphtheritic cardiomyopathy
ICD-10-CM Codes›A00–B99›A30-A49›A36
- Billable — Valid for Submission
- CC — Complication or Comorbidity
- Risk Adjusts — HCC 227
- Not Chronic
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. As a secondary diagnosis, it counts as a complication or comorbidity (CC) and moves an inpatient stay to a higher severity level within its MS-DRG family. It does not count, however, when the principal diagnosis is one of 31 closely related codes. 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.
For Medicare Advantage risk adjustment, A36.81 maps to CMS-HCC Category 227 (Cardiomyopathy/Myocarditis) under the V28 model, adding a risk factor of about 0.189 for a community, non-dual, aged beneficiary in payment year 2026.
Code Identity
Code Classification
Medicare Risk Adjustment (HCC)Billing
A36.81 maps to a payment category in the CMS-HCC model used to risk-adjust Medicare Advantage payments. Weights are the published community factors for payment year 2026.
Source: CMS Payment Year 2026 risk adjustment mappings and model software. Weights are relative factors, not dollar amounts; a beneficiary's total RAF also includes demographics and interactions. Browse all CMS-HCC categories.
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
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.
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
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.
Code HistoryHistory
Questions About A36.81Overview
What is the ICD-10 code for diphtheritic cardiomyopathy?
The ICD-10-CM code for diphtheritic cardiomyopathy is A36.81 (sometimes written as A3681). It is billable on HIPAA-covered claims from October 1, 2025 through September 30, 2026.
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.
Is A36.81 a CC or MCC?
CMS lists A36.81 as a CC (complication or comorbidity) for FY 2026. Reported as a secondary diagnosis, it moves the inpatient stay to a higher-weighted DRG within its severity family. It does not count when the principal diagnosis is one of the 31 closely related codes in its exclusion list.
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.
What HCC is A36.81?
A36.81 (diphtheritic cardiomyopathy) maps to CMS-HCC Category 227 (Cardiomyopathy/Myocarditis), commonly written as HCC 227, in the CMS-HCC V28 model used for Medicare Advantage risk adjustment in payment year 2026. It mapped to HCC 85 under the retired V24 model. It also maps in the PACE (CMS-HCC V22), ESRD (V21), and ESRD (V24) models. In the Part D prescription drug model it maps to RxHCC 186.
Does A36.81 risk-adjust for Medicare Advantage payment?
Yes. When documented and reported on a Medicare Advantage encounter, A36.81 adds a risk adjustment factor of about 0.189 to the beneficiary's RAF score for a community, non-dual, aged enrollee (published V28 weights range from 0.145 to 0.200 depending on the payment segment). A more severe related category (HCC 221, HCC 222, HCC 223, HCC 224, HCC 225, and HCC 226) supersedes it when both are reported. See the full factor table on the HCC 227 category page.
