2026 ICD-10-CM Diagnosis Code Q21.23Complete atrioventricular septal defect

ICD-10-CM Codes›Q00-Q99›Q20-Q28›Q21

ICD-10-CM Q21.23
CMSSource: CMS FY 2026 ICD-10-CM dataset · Effective Oct 1, 2025 – Sep 30, 2026

Q21.23 is a billable ICD-10-CM diagnosis code for complete atrioventricular septal defect. It is valid on HIPAA claims for fiscal year 2026 (October 1, 2025 through September 30, 2026) and groups to MS-DRG 306 through 307. The code is exempt from POA reporting. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Cardiac and circulatory congenital anomalies.

Code Identity

ICD-10-CM Code
Q21.23
Billable Status
Yes — Valid for Submission
Code Describes
Complete atrioventricular septal defect
Short Description
Complete atrioventricular septal defect
Same as the full description in the CMS dataset.
Parent Code
Q21.2
Atrioventricular septal defect

Code Classification

ChapterQ00-Q99Congenital malformations, deformations and chromosomal abnormalities
SectionQ20-Q28Congenital malformations of the circulatory system
CategoryQ21Congenital malformations of cardiac septa
This CodeQ21.23Complete atrioventricular septal defect

Present on Admission (POA)Billing

Q21.23 is exempt from POA reporting on inpatient claims to general acute care hospitals. Review other POA exempt codes.

Approximate SynonymsGuidance

Alternate terms and clinical phrases that map to this code.

  • Abnormality of common atrioventricular valve chordae tendinae
  • Abnormality of common atrioventricular valve in atrioventricular septal defect
  • Abnormality of common atrioventricular valve papillary muscle
  • Accessory tissue on common atrioventricular valve leaflet
  • Arcade abnormality of common atrioventricular valve chordae
  • Atrioventricular septal defect and common atrioventricular junction
  • Atrioventricular septal defect with common atrioventricular orifice
  • Atrioventricular septal defect, atrial and ventricular components with common atrioventricular valve with unbalanced commitment of valve to left ventricle
  • Atrioventricular septal defect, atrial and ventricular components with common atrioventricular valve with unbalanced commitment of valve to right ventricle
  • Atrioventricular septal defect: atrial and ventricular components
  • Common atrioventricular canal
  • Common atrioventricular junction
  • Common atrioventricular junction with spontaneous fibrous closure of atrioventricular septal defect
  • Common atrioventricular orifice in double inlet ventricle
  • Common atrioventricular valve chordae to outlet septum
  • Common atrioventricular valve chordae too long
  • Common atrioventricular valve chordae too short
  • Common atrioventricular valve prolapse
  • Common atrioventricular-type ventricular septal defect
  • Common atrium
  • Common atrium with common atrioventricular junction
  • Congenital cleft of cardiac valve
  • Double orifice of common atrioventricular valve
  • Endocardial cushion defect
  • Fused common atrioventricular valve papillary muscle
  • Hypoplasia of common atrioventricular valve
  • Hypoplastic common atrioventricular valve papillary muscle
  • Parachute malformation of common atrioventricular valve
  • Triple orifice of left ventricular component of common atrioventricular valve
  • True cleft of common atrioventricular valve leaflet

Tabular List NotesGuidance

Coding notes and annotation back-references applicable to this code.

Inclusion Terms

  • 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

Index to Diseases and InjuriesGuidance

Alphabetical index entries that point to this code.

External Cause of Injuries IndexGuidance

References for this code in the External Cause of Injuries Index.

    • 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

Clinical ClassificationClinical

AHRQ’s CCSR groups this code into broader clinical categories.

CCSR MAL001
Cardiac and circulatory congenital anomalies
Default principal diagnosis: inpatient Yes · outpatient Yes

Patient EducationClinical

Congenital Heart Defects

Congenital heart defects (CHDs) are problems with the structure of the heart. "Congenital" means that that the problems are present at birth. These defects happen when a fetus's heart doesn't develop normally during pregnancy. Congenital heart defects are the most common type of birth defect.

The full article covers:

  • What are congenital heart defects?
  • What causes congenital heart defects?
  • Who is more likely to have a baby with a congenital heart defect?
  • What are the symptoms of congenital heart defects?
  • What other problems do congenital heart defects cause?
  • How are congenital heart defects diagnosed?
  • What are the treatments for congenital heart defects?

Read the full article at MedlinePlus

Courtesy of MedlinePlus, a service of the U.S. National Library of Medicine.

Code History & ChangesHistory

Replacement Q21.23 replaces the following previously assigned code(s):

  • Q21.2 - Atrioventricular septal defect
FY 2023AddedAdded to the ICD-10-CM code setEffective October 1, 2022.
FY 2024–2025No changes
FY 2026CurrentCurrent code set, no changesEffective October 1, 2025 through September 30, 2026.

Questions About Q21.23Overview

Is Q21.23 (Atrioventricular septal defect) a billable code?

Yes. This is a billable ICD-10-CM code, specific enough to report complete atrioventricular septal defect on HIPAA-covered claims from October 1, 2025 through September 30, 2026.

What MS-DRG does Q21.23 group to?

When complete atrioventricular septal defect is the principal diagnosis on an inpatient stay, it groups to MS-DRG 306, 307, with relative weights from 0.9132 to 1.5758 depending on complications. Higher weights mean higher Medicare reimbursement.

Is Q21.23 exempt from POA reporting?

Yes. CMS lists this code among those exempt from present on admission reporting, so hospitals do not assign a POA indicator for complete atrioventricular septal defect on inpatient claims.

Footnotes

[1] Chronic - a chronic condition code indicates a condition lasting 12 months or longer and its effect on the patient based on one or both of the following criteria:

  • The condition results in the need for ongoing intervention with medical products,treatment, services, and special equipment
  • The condition places limitations on self-care, independent living, and social interactions.