I40 vs I51.4
I40 and I51.4 can never be reported together. ICD-10-CM declares them mutually exclusive with an Excludes1 note, meaning the two conditions cannot occur in the same patient — so exactly one of them is correct for any given encounter.
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 (diffuse) (obliterans) (of) (senile) (with calcification)
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