Q21.20 Atrioventricular septal defect, unspecified as to partial or complete

Billable ICD-10-CM code, FY2026. Acts as a Complication or Comorbidity (CC) as a secondary diagnosis. Exempt from present-on-admission (POA) reporting.

Applicable to

• Atrioventricular canal, NOS
• Endocardial cushion defect NOS
• Ostium primum atrial septal defect (type I) NOS

Applies from Q21 Congenital malformations of cardiac septa

Excludes1 (never code together)

• acquired cardiac septal defect (I51.0)

Applies from Q21.2 Atrioventricular septal defect

Applicable to

• Atrioventricular canal defect
• Endocardial cushion defect
• Ostium primum atrial septal defect (type I)

Risk adjustment (HCC)

• RxHCC V08: HCC 191 — Ventricular Septal Defect and Major Congenital Heart Disorders

MS-DRG index

Defines the logic of DRG(s) 306-307 in MDC 05.

Code annotations containing back-references to Q21.20

Back-references to Q21.20

• Type 2 Excludes: Q21.1 Atrial septal defect ("ostium primum atrial septal defect (type I) (Q21.20)")

Back-references to Q21.2

• Code Also: Q90 Down syndrome ("associated physical condition(s), such as atrioventricular septal defect (Q21.2-)")

Back-references to Q21

• Code Also: I27.21 Secondary pulmonary arterial hypertension ("congenital heart disease (Q20-Q28)")
• Type 2 Excludes: P29 Cardiovascular disorders originating in the perinatal period ("congenital malformations of the circulatory system (Q20-Q28)")
• Code Also: Q87.85 MED13L syndrome ("congenital malformations of cardiac septa (Q21.-)")
• Code Also: Z71.87 Encounter for pediatric-to-adult transition counseling ("congenital malformations of the circulatory system (Q20-Q28)")

Diagnosis Index entries for Q21.20

• Canal › atrioventricular
• Defect, defective › atrial septal › ostium primum type (type I)
• Defect, defective › atrioventricular › canal
• Defect, defective › atrioventricular › septal › unspecified as to partial or complete
• Defect, defective › atrioventricular › septum
• Defect, defective › cushion, endocardial
• Defect, defective › ostium › primum
• Endocardium, endocardial › cushion defect
• Imperfect › closure (congenital) › atrioventricular ostium
• Ostium › primum (arteriosum) (defect) (persistent)
• Persistence, persistent (congenital) › atrioventricular canal
• Persistence, persistent (congenital) › ostium › primum
• Single › atrium

Nearby codes

• Q21.14 Superior sinus venosus atrial septal defect
• Q21.15 Inferior sinus venosus atrial septal defect
• Q21.16 Sinus venosus atrial septal defect, unspecified
• Q21.19 Other specified atrial septal defect
• Q21.2 Atrioventricular septal defect
• Q21.20 Atrioventricular septal defect, unspecified as to partial or complete (this code)
• Q21.21 Partial atrioventricular septal defect
• Q21.22 Transitional atrioventricular septal defect
• Q21.23 Complete atrioventricular septal defect
• Q21.3 Tetralogy of Fallot
• Q21.4 Aortopulmonary septal defect