I45.9 vs R55
I45.9 and R55 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 R55
Stokes-Adams attack (I45.9)
I45.9
Conduction disorder, unspecified
BillableUnspecified
- Chapter 9
- Diseases of the circulatory system
- Section
- I30-I5A
Use when the record says
- Heart block NOS
- Stokes-Adams syndrome
Indexed under
- Adams-Stokesdisease or syndrome (-Morgagni)
- Dropped heart beats
- Morgagni-Stokes-Adams syndrome
- Spens' syndrome (syncope with heart block)
- Stokes-Adams disease or syndrome
R55
Syncope and collapse
Billable
- Chapter 18
- Symptoms, signs and abnormal clinical and laboratory findings, not elsewhere classified
- Section
- R50-R69
Use when the record says
- Blackout
- Fainting
- Vasovagal attack
Indexed under
- Blackout
- Collapse
- Fainting (fit)
- Near-syncope
- Pre-syncope
These two codes sit in different chapters of the Tabular List, which is usually the clearest signal that they describe different underlying processes rather than different degrees of the same one.
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