FY2027
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Excludes1 pair

I40- vs I51.4

I40 and I51.4 are not coded together. ICD-10-CM declares them mutually exclusive with an Excludes1 note — the two conditions are not expected to occur together, so exactly one of them is normally correct for a given encounter. The Official Guidelines carve out one exception: if the two conditions are clearly unrelated to each other, both may be reported.

The official note, declared on I51.4
acute or subacute myocarditis (I40.-)
I40

Acute myocarditis

Not billable
Chapter 9
Diseases of the circulatory system
Section
I30-I5A
Use when the record says
  • subacute myocarditis
I51.4

Myocarditis, unspecified

BillableUnspecified
Chapter 9
Diseases of the circulatory system
Section
I30-I5A
Use when the record says
  • Chronic (interstitial) myocarditis
  • Myocardial fibrosis
  • Myocarditis NOS
Indexed under
  • Acardiotrophia
  • Myocarditis (with arteriosclerosis)(chronic)(fibroid) (interstitial) (old) (progressive) (senile)
  • Arteriosclerosis, arteriosclerotic › myocarditis

Excludes1 is not always absolute: where two conditions covered by the note are genuinely unrelated, CMS guidance permits reporting both. Document the reasoning rather than assuming it. More on Excludes1 vs Excludes2 · FY2027