A36.81 ICD-10-CM Code: Diphtheritic cardiomyopathy
A36.81 maps to CMS-HCC V28 227. A source-labeled RAF reference is available. Confirm the documented diagnosis and applicable coding requirements. MEAT criteria · RAF Calculator · HCC Buddy coding tools
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FY 2026 Apr update / Certain infectious and parasitic diseases (A00-B99) / Other bacterial diseases (A30-A49)
A36.81
Billable / SpecificICD-10-CMOfficial ICD-10-CMCodebook guidanceDiphtheritic cardiomyopathy
This is a serious heart muscle infection caused by diphtheria bacteria that weakens the heart's ability to pump blood effectively. It occurs when diphtheria toxin damages the heart tissue, potentially leading to heart failure or irregular heartbeats.
Buddy Insight
Diphtheritic cardiomyopathy is a life-threatening cardiac complication of Corynebacterium diphtheriae infection, caused by diphtheria toxin damaging the myocardium.
CMS-HCC V28
MappedHCC 227
Coefficient HCC 227: 0.189 (Community Non-Dual Aged (CNA))
CMS-HCC V24
HistoricalHistorical
Not used for CY2026 payment
ACA/HHS
MappedHCC 130
Code-level coefficient reference
ESRD/PACE
MappedHCC 85
Code-level coefficient reference
RXHCC
MappedHCC 186
Code-level coefficient reference
Code Book Path
Inclusion Terms
Official- Diphtheritic myocarditis
Excludes 2
Official- carrier or suspected carrier of infectious disease (Z22.-)Inherited from A00-B99
- infectious and parasitic diseases complicating pregnancy, childbirth and the puerperium (O98.-)Inherited from A00-B99
- infectious and parasitic diseases specific to the perinatal period (P35-P39)Inherited from A00-B99
- influenza and other acute respiratory infections (J00-J22)Inherited from A00-B99
Related Codes
Includes
Official- diseases generally recognized as communicable or transmissibleInherited from A00-B99
Excludes 1
Official- certain localized infections - see body system-related chaptersInherited from A00-B99
Code First
OfficialNo Code First sequencing instructions are included in this display for A36.81. Check the code and parent instructions in the Code Book.
Use Additional
Official- code to identify resistance to antimicrobial drugs (Z16.-)Inherited from A00-B99
Code Also
OfficialNo Code Also instructions are included in this display for A36.81. Check the code and parent instructions in the Code Book.
Buddy Documentation Tip
MEAT Support
Audit Caution
Common Mistakes
Current with CMS: FY2026 ICD-10-CM Apr 1 update (effective Apr 1 – Sep 30, 2026) · CMS-HCC V28, 100% phased in for payment year 2026. FY2027 code set already staged for October 1, 2026. How HCC Buddy stays current →
Is A36.81 an HCC code?
Yes. A36.81 (Diphtheritic cardiomyopathy) maps to HCC 227, Cardiomyopathy/Myocarditis under the CMS-HCC V28 risk adjustment model, with a source-labeled community non-dual aged reference coefficient of 0.189. Source-labeled code-level coefficients are references, not member totals. Actual contribution depends on complete member context, hierarchy and cleanup rules, interactions, and model year. HCC Buddy's RAF Calculator supports CMS-HCC V28 PY2026 and shows no score unless every required source and calculation check passes. It is billable for payment year 2026.
Coder answer: A36.81 is billable and maps to V28 HCC 227, Cardiomyopathy/Myocarditis. Open it in the Code Book for the tabular path, RAF, and MEAT checklist.
- Code
- A36.81
- Description
- Diphtheritic cardiomyopathy
- HCC (V28)
- HCC 227 — Cardiomyopathy/Myocarditis
- RAF reference coefficient
- 0.189
- Billable
- Yes
- Payment year
- 2026
HCC Category Mapping
These are source-labeled model coefficients, not member totals. A category may still be removed by hierarchy or model cleanup rules. Weights are not directly comparable across models: CMS-HCC V28 and V24 use Community, Non-Dual, Aged; ESRD uses the dialysis continuing-enrollee model; RxHCC is the Part D continuing-enrollee, non-low-income, aged weight (a larger scale than CMS-HCC). ACA/HHS has no single weight — it varies by metal level. Actual per-patient RAF contribution depends on member context, hierarchy and cleanup rules, interactions, and the model year used by the payer. V28 is the CMS-HCC model phased in over payment years 2024–2026; V24 remains available for historical review.
Work A36.81 in the Code Book — tabular path, V28 RAF reference, and MEAT checklist →
MEAT review for A36.81
For A36.81, confirm that the documentation supports the diagnosis and meets the applicable coding, encounter, program and payer requirements. MEAT (Monitor, Evaluate, Assess, or Treat) is a review mnemonic, not a universal CMS coding rule.
- MMonitor: signs, symptoms, disease progression, or lab trending documented in the note
- EEvaluate: test results, medication response, or physical findings reviewed by the provider
- AAssess: explicit mention in the assessment or plan with acknowledgment of status
- TTreat: medication, referral, procedure, therapy, or counseling tied to the diagnosis
Coder workflow notes
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What This Code Means
A36.81 is the ICD-10-CM diagnosis code for diphtheritic cardiomyopathy. This is a serious heart muscle infection caused by diphtheria bacteria that weakens the heart's ability to pump blood effectively. It occurs when diphtheria toxin damages the heart tissue, potentially leading to heart failure or irregular heartbeats. A36.81 sits in the ICD-10-CM chapter for certain infectious and parasitic diseases (a00-b99), within the section covering other bacterial diseases (a30-a49).
Under the CMS-HCC V28 risk adjustment model, A36.81 maps to Cardiomyopathy/Myocarditis (HCC 227) with a source-labeled community, non-dual, aged reference coefficient of 0.189. No V24 mapping is shown for A36.81; use the applicable model and payment year when reviewing the V28 mapping. For CY2026 non-PACE Medicare Advantage, CMS uses 100% of the 2024 CMS-HCC model (V28). PACE uses a separate model blend. Source-labeled code-level coefficients are references, not member totals. Actual contribution depends on complete member context, hierarchy and cleanup rules, interactions, and model year. HCC Buddy's RAF Calculator supports CMS-HCC V28 PY2026 and shows no score unless every required source and calculation check passes.
This code should only be used when diphtheria has been confirmed and documented as causing cardiomyopathy; do not code presumptively. For A36.81, confirm that the documentation supports the diagnosis and meets the applicable coding, encounter, program and payer requirements. MEAT (Monitor, Evaluate, Assess, or Treat) is a review mnemonic, not a universal CMS coding rule. When documentation is ambiguous, coders should issue a provider query rather than assume the highest-specificity variant.
HCC Buddy maintains structured V28 and V24 mapping, source-labeled coefficient references, and MEAT documentation criteria for A36.81 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.
Coding Tips
- •This code should only be used when diphtheria has been confirmed and documented as causing cardiomyopathy; do not code presumptively
- •Verify that the primary diphtheria diagnosis (A36.x) is also coded separately, as A36.81 is a manifestation code that requires the underlying diphtheria condition to be reported
Clinical Significance
Diphtheritic cardiomyopathy is a life-threatening cardiac complication of Corynebacterium diphtheriae infection, caused by diphtheria toxin damaging the myocardium. It can lead to heart failure, conduction abnormalities, and sudden death. This complication typically occurs 1-2 weeks after onset of pharyngeal diphtheria and is a major cause of diphtheria-related mortality.
Documentation Requirements
- ✓Confirmed or suspected diphtheria infection with cardiac involvement
- ✓Echocardiogram showing ventricular dysfunction or wall motion abnormalities
- ✓ECG findings (conduction delays, ST-T changes, arrhythmias)
- ✓Cardiac biomarkers (troponin, BNP/NT-proBNP) documenting myocardial injury
- ✓Timeline correlation between diphtheria onset and cardiac symptoms
Commonly Confused Codes
- •A36.0 (Pharyngeal diphtheria): A36.0 is uncomplicated pharyngeal diphtheria; A36.81 specifically captures the cardiac complication
- •I42.9 (Cardiomyopathy, unspecified): Use A36.81 when cardiomyopathy is caused by diphtheria, not the generic cardiomyopathy code
- •I40.0 (Infective myocarditis): A36.81 is the specific combination code for diphtheria-related myocardial disease