FY2027
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Excludes1 pair

I45.9 vs R55

I45.9 and R55 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 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-Stokes disease 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