A36.81
BillableDiphtheritic cardiomyopathy
Last updated: FY2026 ICD-10-CM (Oct 1, 2025 – Sep 30, 2026) | CMS-HCC V28 (100% phase-in, PY2026)
Is A36.81 an HCC code?
Yes. A36.81 maps to Cardiomyopathy under the CMS-HCC V28 risk adjustment model (and Congestive Heart Failure under V24).
HCC Category Mapping
RAF weights shown are the community, non-dual, aged base weights from the CMS risk adjustment model file. Actual per-patient RAF contribution depends on member segment, interactions, and the model year used by the payer. V28 is the CMS-HCC model phased in over payment years 2024–2026; V24 remains in use during the transition and for historical data.
MEAT Criteria for A36.81
For A36.81 to count as a valid HCC diagnosis in a given encounter, the provider's documentation must show MEAT: Monitor, Evaluate, Assess, or Treat. A diagnosis from a prior year does not carry forward automatically — it has to be re-documented and supported each calendar year.
- 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
Only one of M/E/A/T is required to support the code, but the documentation must be specific enough to show that the provider actually addressed A36.81 during that encounter — not just copy-forwarded from a problem list.
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 (HCC 227) with a community, non-dual, aged base RAF weight of 0.339. Under the older CMS-HCC V24 model, A36.81 maps to Congestive Heart Failure (HCC 85) with a community, non-dual, aged base RAF weight of 0.368. V28 is the CMS-HCC risk adjustment model that reached 100% phase-in for payment year 2026, replacing V24 which was used during the PY2024–PY2025 transition.
This code should only be used when diphtheria has been confirmed and documented as causing cardiomyopathy; do not code presumptively. Because A36.81 maps to a payment HCC, the provider's documentation must satisfy MEAT criteria (Monitor, Evaluate, Assess, or Treat) for the encounter to count toward the patient's Medicare Advantage risk adjustment score. 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, RAF weights, 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