Q21.23
Complete atrioventricular septal defect
Q21.23 (also written Q2123) is a billable ICD-10-CM diagnosis code for complete atrioventricular septal defect. It is part of the FY2027 code set, effective October 1, 2026. It is one of the 17 codes in category Q21 (Congenital malformations of cardiac septa). The Alphabetic Index lists it under 8 entries. Its coding notes include 1 Excludes1 entry and 1 Excludes2 entry.
Guidelines tip
From the FY2027 Official Guidelines. ICD10Ref adds no rules of its own.
Chapter 17 codes can be used for life. Manifestations that are an inherent part of a specifically coded anomaly are not coded separately. A corrected malformation is reported with a personal history code.
Excludes1
Not coded here. The listed conditions generally should not be reported together.
Excludes2
Not included here. Both codes may be reported if the patient has both conditions.
Also from chapter/block level (1 note)
- inborn errors of metabolism (E70-E88)
Care settings
How CMS programs treat this code. These are CMS claim edits and list entries, not coverage or eligibility rules.
Home Health Primary
Accepted as the primary (principal) diagnosis on a home health claim. The Home Health Grouper assigns it to the MMTA - Other clinical group.
Source: CMS Home Health Grouper Software v07.2.26, effective October 1, 2026Hospital CC
Counts as a complication or comorbidity (CC) when reported as a secondary diagnosis on an inpatient claim. It does not count when the principal diagnosis is one of the 60 codes in its exclusion list. Some MS-DRGs also ignore a CC or MCC that defines the DRG.
Source: CMS MS-DRG Definitions Manual v44, effective October 1, 2026, Appendix CInclusion terms
Conditions classified to this code.
- Common atrioventricular canal
- Common atrioventricular septal defect
- Common endocardial cushion defect
- Ostium primum atrial septal defect (type I) with common atrioventricular valve and a moderate or larger inlet VSD
Notes
Also from chapter/block level (1 note)
- Codes from this chapter are not for use on maternal records
Alphabetic Index terms
Terms the official Alphabetic Index lists for this code. 8 entries
- Canal, atrioventricular, common
- Common, atrioventricular canal
- Defect, defective, atrial septal, ostium primum type (type I), with, common atrioventricular valves and moderate or larger inlet VSD
- Defect, defective, atrioventricular, septal, common
- Defect, defective, atrioventricular, septal, complete
- Defect, defective, cushion, endocardial, common
- Ostium, atrioventriculare commune
- Persistence, persistent (congenital), ostium, atrioventriculare commune