FY2027
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Excludes1 pair

Q23.0 vs Q23.4

Q23.0 and Q23.4 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 Q23.0
congenital stenosis of aortic valve in hypoplastic left heart syndrome (Q23.4)
Q23.0

Congenital stenosis of aortic valve

Billable
Chapter 17
Congenital malformations, deformations, chromosomal abnormalities, and genetic disorders
Section
Q20-Q28
Use when the record says
  • Congenital aortic atresia
  • Congenital aortic stenosis NOS
Indexed under
  • Atresia, atretic › aortic (orifice) (valve)
  • Stenosis, stenotic › aortic › congenital
  • Stenosis, stenotic › valve › congenital › aortic
  • Stricture › heart › valve › aortic
  • Stricture › valve › congenital › aortic
Q23.4

Hypoplastic left heart syndrome

Billable
Chapter 17
Congenital malformations, deformations, chromosomal abnormalities, and genetic disorders
Section
Q20-Q28
Indexed under
  • Hypoplasia, hypoplastic › left heart syndrome
  • Syndrome › hypoplastic left-heart
  • Atresia, atretic › aortic › congenital with hypoplasia of ascending aorta and defective development of left ventricle (with mitral stenosis)
  • Atresia, atretic › aortic › in hypoplastic left heart syndrome
  • Atresia, atretic › mitral valve › in hypoplastic left heart syndrome

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