ICD-10-CM 2027
ICD-10 code for atrial septal defect
From the official ICD-10-CM alphabetic index entry “Defect, defective › atrial septal”. Page updated September 29, 2026.
About coding atrial septal defect
The ICD-10-CM code for atrial septal defect is Q21.10 (Atrial septal defect, unspecified). The official index lists 13 more specific codes, so check the documentation for details such as type, cause, site or severity before settling on Q21.10.
Within Q21.1, choose Q21.10 (unspecified) only when documentation doesn't support a more specific option: secundum atrial septal defect (Q21.11), Patent foramen ovale (Q21.12), coronary sinus atrial septal defect (Q21.13), superior sinus venosus atrial septal defect (Q21.14), inferior sinus venosus atrial septal defect (Q21.15), sinus venosus atrial septal defect, unspecified (Q21.16) and other specified atrial septal defect (Q21.19).
As a secondary diagnosis it is a CC (complication or comorbidity), which can move an inpatient stay into the "with CC" MS-DRG of its family, unless the principal diagnosis excludes it.
In MS-DRG v44.0, it is part of the grouping logic for DRG 306 (Cardiac Congenital and Valvular Disorders with MCC, relative weight 1.546) and DRG 307 (Cardiac Congenital and Valvular Disorders without MCC, relative weight 0.9148), in MDC 05 (Diseases and Disorders of the Circulatory System), as a principal or secondary diagnosis. The DRG a claim lands in depends on the principal diagnosis, procedures and any CC/MCC secondary diagnoses.
More specific atrial septal defect codes (official index)
- coronary sinus Q21.13 — Coronary sinus atrial septal defect
- following acute myocardial infarction (current complication) I23.1 — Atrial septal defect as current complication following acute myocardial infarction
- ostium primum type (type I) Q21.20 — Atrioventricular septal defect, unspecified as to partial or complete
- with
- common atrioventricular valves and moderate or larger inlet VSD Q21.23 — Complete atrioventricular septal defect
- separate atrioventricular valves Q21.21 — Partial atrioventricular septal defect
- and small or restrictive inlet VSD Q21.22 — Transitional atrioventricular septal defect
- ostium secundum type (patent persistent) (type II) Q21.11 — Secundum atrial septal defect
- sinus venosus Q21.16 — Sinus venosus atrial septal defect, unspecified
- inferior Q21.15 — Inferior sinus venosus atrial septal defect
- superior Q21.14 — Superior sinus venosus atrial septal defect
- specified NEC Q21.19 — Other specified atrial septal defect
- vena cava type
- inferior Q21.15 — Inferior sinus venosus atrial septal defect
- superior Q21.14 — Superior sinus venosus atrial septal defect
Common questions about atrial septal defect ICD-10 codes
What is the ICD-10 code for atrial septal defect?
- Q21.10 — Atrial septal defect, unspecified. More specific codes apply when the documentation supports them: Q21.13, I23.1, Q21.20, Q21.23 and others below.
What is the ICD-10 code for coronary sinus atrial septal defect?
- Q21.13 — Coronary sinus atrial septal defect.
What is the ICD-10 code for ostium primum type atrial septal defect?
- Q21.20 — Atrioventricular septal defect, unspecified as to partial or complete.
What is the ICD-10 code for ostium secundum type atrial septal defect?
- Q21.11 — Secundum atrial septal defect.
What is the ICD-10 code for sinus venosus atrial septal defect?
- Q21.16 — Sinus venosus atrial septal defect, unspecified.
Is Q21.10 billable?
- Yes. Q21.10 is a billable/specific ICD-10-CM code valid for FY2027 (October 1, 2026 – September 30, 2027).
Can Q21.10 be used as a principal diagnosis?
- Yes. The Medicare Code Editor doesn't restrict Q21.10 as a principal diagnosis.
Is Q21.10 a CC or MCC?
- Q21.10 is a CC (complication or comorbidity) under MS-DRG v44.0, unless excluded by the principal diagnosis.