Q21.20CurrentBillable / specificExempt from present-on-admission reporting

Atrioventricular septal defect, unspecified as to partial or complete

Q21 · Inherited instructions

Excludes 1

acquired cardiac septal defect (I51.0)

Excludes 2 · 1

Chapters 17 · Congenital malformations, deformations and chromosomal abnormalities (Q00-QA0)

Excludes 2

inborn errors of metabolism (E70-E88)

Claims & coverage

Coverage depends on the payer, service and applicable policy. A billable code does not guarantee payment.

When ICD-10-CM is required

For US diagnosis claims covered by HIPAA, ICD-10-CM is required from October 1, 2015.

Use the service date for outpatient/professional claims and the discharge date for hospital inpatient claims. Earlier encounters use ICD-9-CM; each individual code must also be valid for the applicable date.

Official coding guidelines → · CMS ↗

MS-DRG · 43.1 · 306, 307

Grouping depends on the complete encounter and CMS grouper logic.

306 · Cardiac Congenital and Valvular Disorders with MCC
307 · Cardiac Congenital and Valvular Disorders without MCC

2026-04-01 – 2026-09-30

CMS · MS-DRG 43.1

Check Medicare coverage ↗

First observed · 2022-10-01

Code history

Latest recorded change · FY2023

ChangedUnchanged

FY2023

Effective from 2022-10-01

Added

Atrioventricular septal defect, unspecified as to partial or complete

Billable diagnosis code

CDC/NCHS · FY2023

All editions (9)

All editions	Effective from	Code history
FY2023	2022-10-01	Added
FY2023 · 04-01	2023-04-01	No tabular change
FY2024	2023-10-01	No tabular change
FY2024 · 04-01	2024-04-01	No tabular change
FY2025	2024-10-01	No tabular change
FY2025 · 04-01	2025-04-01	No tabular change
FY2026	2025-10-01	No tabular change
FY2026 · April	2026-04-01	No tabular change
FY2027	2026-10-01	No tabular change

Code-level instructions

Includes

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

Inherited instructions

Chapters 17 · Congenital malformations, deformations and chromosomal abnormalities (Q00-QA0)

Excludes 2

inborn errors of metabolism (E70-E88)

Note

Codes from this chapter are not for use on maternal records

Q21 · Congenital malformations of cardiac septa

Excludes 1

acquired cardiac septal defect (I51.0)

Q21.2 · Atrioventricular septal defect

Includes

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

Official index references (13)

Canal (1)

Canal › atrioventricularDisease index

Defect, defective (6)

Defect, defective › atrial septal › ostium primum type(type I)Disease index
Defect, defective › atrioventricular › canalDisease index
Defect, defective › atrioventricular › septal › unspecified as to partial or completeDisease index
Defect, defective › atrioventricular › septumDisease index
Defect, defective › cushion, endocardialDisease index
Defect, defective › ostium › primumDisease index

Endocardium, endocardial (1)

Endocardium, endocardial › cushion defectDisease index

Imperfect (1)

Imperfect › closure(congenital) › atrioventricular ostiumDisease index

Ostium (1)

Ostium › primum(arteriosum) (defect) (persistent)Disease index

Persistence, persistent(congenital) (2)

Persistence, persistent(congenital) › atrioventricular canalDisease index
Persistence, persistent(congenital) › ostium › primumDisease index

Single (1)

Single › atriumDisease index

Official conversion history

Historical assignments from the CDC conversion table support data retrieval. They do not authorize substituting a previous code for the current code.

Release dates 2022-10-01

Previous assignment: Q21.2

Related codes

Other entries in the same category; these are not automatic substitutes.

Code	Description	Category · further specificity required
Q21.21	Partial atrioventricular septal defect	Billable / specific
Q21.22	Transitional atrioventricular septal defect	Billable / specific
Q21.23	Complete atrioventricular septal defect	Billable / specific

Official titles and instructions are preserved in their source language. Official sources ↗

Q21.20CurrentBillable / specificExempt from present-on-admission reporting

Atrioventricular septal defect, unspecified as to partial or complete

Q21 · Inherited instructions

Excludes 1

acquired cardiac septal defect (I51.0)

Excludes 2 · 1

Chapters 17 · Congenital malformations, deformations and chromosomal abnormalities (Q00-QA0)

Excludes 2

inborn errors of metabolism (E70-E88)

Claims & coverage

Coverage depends on the payer, service and applicable policy. A billable code does not guarantee payment.

When ICD-10-CM is required

For US diagnosis claims covered by HIPAA, ICD-10-CM is required from October 1, 2015.

Official coding guidelines → · CMS ↗

MS-DRG · 43.1 · 306, 307

Grouping depends on the complete encounter and CMS grouper logic.

306 · Cardiac Congenital and Valvular Disorders with MCC
307 · Cardiac Congenital and Valvular Disorders without MCC

2026-04-01 – 2026-09-30

CMS · MS-DRG 43.1

Check Medicare coverage ↗

First observed · 2022-10-01

Code history

Latest recorded change · FY2023

ChangedUnchanged

FY2023

Effective from 2022-10-01

Added

Atrioventricular septal defect, unspecified as to partial or complete

Billable diagnosis code

CDC/NCHS · FY2023

All editions (9)

All editions	Effective from	Code history
FY2023	2022-10-01	Added
FY2023 · 04-01	2023-04-01	No tabular change
FY2024	2023-10-01	No tabular change
FY2024 · 04-01	2024-04-01	No tabular change
FY2025	2024-10-01	No tabular change
FY2025 · 04-01	2025-04-01	No tabular change
FY2026	2025-10-01	No tabular change
FY2026 · April	2026-04-01	No tabular change
FY2027	2026-10-01	No tabular change

Code-level instructions

Includes

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

Inherited instructions

Chapters 17 · Congenital malformations, deformations and chromosomal abnormalities (Q00-QA0)

Excludes 2

inborn errors of metabolism (E70-E88)

Note

Codes from this chapter are not for use on maternal records

Q21 · Congenital malformations of cardiac septa

Excludes 1

acquired cardiac septal defect (I51.0)

Q21.2 · Atrioventricular septal defect

Includes

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

Official index references (13)

Canal (1)

Canal › atrioventricularDisease index

Defect, defective (6)

Defect, defective › atrial septal › ostium primum type(type I)Disease index
Defect, defective › atrioventricular › canalDisease index
Defect, defective › atrioventricular › septal › unspecified as to partial or completeDisease index
Defect, defective › atrioventricular › septumDisease index
Defect, defective › cushion, endocardialDisease index
Defect, defective › ostium › primumDisease index

Endocardium, endocardial (1)

Endocardium, endocardial › cushion defectDisease index

Imperfect (1)

Imperfect › closure(congenital) › atrioventricular ostiumDisease index

Ostium (1)

Ostium › primum(arteriosum) (defect) (persistent)Disease index

Persistence, persistent(congenital) (2)

Persistence, persistent(congenital) › atrioventricular canalDisease index
Persistence, persistent(congenital) › ostium › primumDisease index

Single (1)

Single › atriumDisease index

Official conversion history

Historical assignments from the CDC conversion table support data retrieval. They do not authorize substituting a previous code for the current code.

Release dates 2022-10-01

Previous assignment: Q21.2

Related codes

Other entries in the same category; these are not automatic substitutes.

Code	Description	Category · further specificity required
Q21.21	Partial atrioventricular septal defect	Billable / specific
Q21.22	Transitional atrioventricular septal defect	Billable / specific
Q21.23	Complete atrioventricular septal defect	Billable / specific

Official titles and instructions are preserved in their source language. Official sources ↗