ICD-10-CM 2027
ICD-10 code for atrium single
Atrioventricular septal defect, unspecified as to partial or complete
From the official ICD-10-CM alphabetic index entry “Single › atrium”. Page updated September 29, 2026.
About coding atrium single
The ICD-10-CM code for atrium single is Q21.20 (Atrioventricular septal defect, unspecified as to partial or complete).
Within Q21.2, choose Q21.20 (unspecified as to partial or complete) only when documentation doesn't support a more specific option: partial atrioventricular septal defect (Q21.21), Transitional atrioventricular septal defect (Q21.22) and complete atrioventricular septal defect (Q21.23).
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.
Common questions about atrium single ICD-10 codes
What is the ICD-10 code for atrium single?
- Q21.20 — Atrioventricular septal defect, unspecified as to partial or complete.
Is Q21.20 billable?
- Yes. Q21.20 is a billable/specific ICD-10-CM code valid for FY2027 (October 1, 2026 – September 30, 2027).
Can Q21.20 be used as a principal diagnosis?
- Yes. The Medicare Code Editor doesn't restrict Q21.20 as a principal diagnosis.
Is Q21.20 a CC or MCC?
- Q21.20 is a CC (complication or comorbidity) under MS-DRG v44.0, unless excluded by the principal diagnosis.