I00 vs I01.0
I00 and I01.0 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.
I00
Rheumatic fever without heart involvement
Billable
- Chapter 9
- Diseases of the circulatory system
- Section
- I00-I02
Use when the record says
- arthritis, rheumatic, acute or subacute
Indexed under
- Fever › rheumatic (inanition) (of unknown origin) (persistent) (with chills) (with rigor)
- Pneumonia › rheumatic (acute) (double) (migratory) (purulent) (septic) (unresolved)
- Rheumatic › pneumonia (acute) (subacute)
- Erythema, erythematous › marginatum › inacute rheumatic fever (infectional) (inflammation)
- Pneumonia › in › rheumatic fever (acute) (double) (migratory) (purulent) (septic) (unresolved)
I01.0
Acute rheumatic pericarditis
Billable
- Chapter 9
- Diseases of the circulatory system
- Section
- I00-I02
Use when the record says
- Any condition in I00 with pericarditis
- Rheumatic pericarditis (acute)
Indexed under
- Pericarditis › rheumatic (with decompensation) (with effusion)
- Rheumatic › pericarditis (acute) (subacute)
- Pericarditis › acute › rheumatic (with decompensation) (with effusion)
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