Q21 – Congenital malformations of cardiac septa
ICD-10-CM 2027 diagnosis code · Congenital malformations of the circulatory system
ICD-10-CM code
Q21
- Code
Q21(claims format:Q21)- Description
- Congenital malformations of cardiac septa
- Billable
- No – use a more specific code below
- Valid for
- Dates of service October 1, 2026 – September 30, 2027 (FY2027)
- Chapter
- 17. Congenital malformations, deformations, chromosomal abnormalities, and genetic disorders (Q00-QA1)
- Block
- Q20-Q28 Congenital malformations of the circulatory system
Billable codes under Q21
Q21 is a header code and cannot be used on claims. Choose the most specific code:
- Q21.0 – Ventricular septal defectBillable
- Q21.1 – Atrial septal defectHeader (more codes below)
- Q21.2 – Atrioventricular septal defectHeader (more codes below)
- Q21.3 – Tetralogy of FallotBillable
- Q21.4 – Aortopulmonary septal defectBillable
- Q21.8 – Other congenital malformations of cardiac septaBillable
- Q21.9 – Congenital malformation of cardiac septum, unspecifiedBillable
Notes for Q21
Excludes1 (not coded here):
- acquired cardiac septal defect (I51.0)
Frequently asked questions
What is ICD-10 code Q21?
Q21 is the ICD-10-CM code for congenital malformations of cardiac septa, in the block Q20-Q28 (Congenital malformations of the circulatory system).
Is Q21 a billable code?
No. Q21 is a header code with more specific child codes; report one of the billable codes listed above.
Source: CDC/NCHS ICD-10-CM FY2027 code files, tabular list and index. Reference only – code assignment must follow the official ICD-10-CM guidelines and documentation in the medical record.