Q23.0 vs Q23.4
Q23.0 and Q23.4 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 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
- Stenosis, stenotic › aortic › congenital (cicatricial)
- Stenosis, stenotic › valve › congenital › aortic (cicatricial)
- 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
- 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