Q21.9 – Congenital malformation of cardiac septum, unspecified

ICD-10-CM 2027 diagnosis code · Congenital malformations of the circulatory system

Billable code

ICD-10-CM code Q21.9

Code: Q21.9 (claims format: Q219)
Description: Congenital malformation of cardiac septum, unspecified
Billable: Yes – valid for HIPAA-covered transactions
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
Parent codes: Q21

Notes for Q21.9

Applicable to:

Septal (heart) defect NOS

Notes inherited from parent codes

Instructional notes at a category or block level apply to every code below it.

Q21 – Congenital malformations of cardiac septa

Excludes1 (not coded here):

acquired cardiac septal defect (I51.0)

Index terms for Q21.9

Entries in the ICD-10-CM alphabetic index that lead to this code:

Related codes in Q21

Q21.0 – Ventricular septal defectBillable
Q21.1 – Atrial septal defectHeader
Q21.2 – Atrioventricular septal defectHeader
Q21.3 – Tetralogy of FallotBillable
Q21.4 – Aortopulmonary septal defectBillable
Q21.8 – Other congenital malformations of cardiac septaBillable

Frequently asked questions

What is ICD-10 code Q21.9?

Q21.9 is the ICD-10-CM code for congenital malformation of cardiac septum, unspecified, in the block Q20-Q28 (Congenital malformations of the circulatory system).

Is Q21.9 a billable code?

Yes. Q21.9 is a billable/specific code that can be used to indicate a diagnosis for reimbursement purposes.

What category does Q21.9 belong to?

It belongs to category Q21 – Congenital malformations of cardiac septa.

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.