I34 vs Q23.9
I34 and Q23.9 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.
Nonrheumatic mitral valve disorders
- Chapter 9
- Diseases of the circulatory system
- Section
- I30-I5A
Congenital malformation of aortic and mitral valves, unspecified
- Chapter 17
- Congenital malformations, deformations, chromosomal abnormalities, and genetic disorders
- Section
- Q20-Q28
- Anomaly, anomalous › aortic cusp or valve (congenital) (unspecified type)
- Anomaly, anomalous › mitral (congenital) (unspecified type)
- Malformation › aortic valve (congenital)
- Malformation › mitral valve (congenital)
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