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ICD-10 Code Q21.20: Atrioventricular septal defect, unspecified as to partial or complete

Q21.20 is a billable ICD-10 diagnosis code used to classify Atrioventricular septal defect, unspecified as to partial or complete in medical records and claims. You may see this code in hospital records, discharge summaries, insurance claims, encounter documentation, referrals, or other healthcare billing and coding records. ICD-10 codes are diagnosis classification codes used in healthcare records, reporting, coding workflows, and billing support. This code sits within the broader ICD-10 area for Congenital malformations, deformations, chromosomal abnormalities, and genetic disorders (Q00-QA0).

Reviewed by HealthAssure Clinical TeamUpdated 26 May 2026

What is this code?

ICD-10 codes are diagnosis classification codes used in healthcare records, reporting, coding workflows, and billing support. This code sits within the broader ICD-10 area for Congenital malformations, deformations, chromosomal abnormalities, and genetic disorders (Q00-QA0).

When is it used?

  • May be used when a clinician documents atrioventricular septal defect, unspecified as to partial or complete in a patient's medical record.
  • May appear in hospital records, claims, referrals, and clinical documentation.
  • This code can be used as a clinically usable diagnosis entry in standardized coding workflows.

What it does not mean

  • A code alone does not explain severity, treatment plan, or outcome.
  • A medical code should not be treated as a substitute for a doctor's diagnosis or advice.

Code hierarchy

chapter
17Congenital malformations, deformations, chromosomal abnormalities, and genetic disorders (Q00-QA0)
block
Q20-Q28Congenital malformations of the circulatory system
category
Q21Congenital malformations of cardiac septa
category
Q21.2Atrioventricular septal defect
currentQ21.2

Official coding notes

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

Where you may see this code

You may see this code in hospital records, discharge summaries, insurance claims, encounter documentation, referrals, or other healthcare billing and coding records.

Coverage-related procedures and services

CPT 93325high
DOPPLER ECHOCARDIOGRAPHY COLOR FLOW VELOCITY MAPPING (LIST SEPARATELY IN ADDITION TO CODES FOR ECHOCARDIOGRAPHY)
Source: CMS coverage guidance
CPT 93320high
DOPPLER ECHOCARDIOGRAPHY, PULSED WAVE AND/OR CONTINUOUS WAVE WITH SPECTRAL DISPLAY (LIST SEPARATELY IN ADDITION TO CODES FOR ECHOCARDIOGRAPHIC IMAGING); COMPLETE
Source: CMS coverage guidance
CPT 93321high
DOPPLER ECHOCARDIOGRAPHY, PULSED WAVE AND/OR CONTINUOUS WAVE WITH SPECTRAL DISPLAY (LIST SEPARATELY IN ADDITION TO CODES FOR ECHOCARDIOGRAPHIC IMAGING); FOLLOW-UP OR LIMITED STUDY (LIST SEPARATELY IN ADDITION TO CODES FOR ECHOCARDIOGRAPHIC IMAGING)
Source: CMS coverage guidance
CPT 93355high
ECHOCARDIOGRAPHY, TRANSESOPHAGEAL (TEE) FOR GUIDANCE OF A TRANSCATHETER INTRACARDIAC OR GREAT VESSEL(S) STRUCTURAL INTERVENTION(S) (EG, TAVR, TRANSCATHETER PULMONARY VALVE REPLACEMENT, MITRAL VALVE REPAIR, PARAVALVULAR REGURGITATION REPAIR, LEFT ATRIAL APPENDAGE OCCLUSION/CLOSURE, VENTRICULAR SEPTAL DEFECT CLOSURE) (PERI-AND INTRA-PROCEDURAL), REAL-TIME IMAGE ACQUISITION AND DOCUMENTATION, GUIDANCE WITH QUANTITATIVE MEASUREMENTS, PROBE MANIPULATION, INTERPRETATION, AND REPORT, INCLUDING DIAGNOSTIC TRANSESOPHAGEAL ECHOCARDIOGRAPHY AND, WHEN PERFORMED, ADMINISTRATION OF ULTRASOUND CONTRAST, DOPPLER, COLOR FLOW, AND 3D
Source: CMS coverage guidance
CPT 93318high
ECHOCARDIOGRAPHY, TRANSESOPHAGEAL (TEE) FOR MONITORING PURPOSES, INCLUDING PROBE PLACEMENT, REAL TIME 2-DIMENSIONAL IMAGE ACQUISITION AND INTERPRETATION LEADING TO ONGOING (CONTINUOUS) ASSESSMENT OF (DYNAMICALLY CHANGING) CARDIAC PUMPING FUNCTION AND TO THERAPEUTIC MEASURES ON AN IMMEDIATE TIME BASIS
Source: CMS coverage guidance
CPT 93314high
ECHOCARDIOGRAPHY, TRANSESOPHAGEAL, REAL-TIME WITH IMAGE DOCUMENTATION (2D) (WITH OR WITHOUT M-MODE RECORDING); IMAGE ACQUISITION, INTERPRETATION AND REPORT ONLY
Source: CMS coverage guidance

Coding guidelines

Common synonyms

Atrioventricular septal defect, unspecified as to partial or completeAtrioventricular septal defect

Frequently asked questions

Code details

CodeQ21.20
SystemICD10
Display nameAtrioventricular septal defect, unspecified as to partial or complete
ChapterCongenital malformations, deformations, chromosomal abnormalities, and genetic disorders (Q00-QA0)
BlockCongenital malformations of the circulatory system

Flags

BillableYes
Valid clinical useYes

Source

SourceICD-10
Version2026-annual
Releaseannual
Year2026

Index terms

Matched terms
CanalDefect, defectiveDefect, defectiveDefect, defectiveDefect, defectiveDefect, defectiveDefect, defectiveEndocardium, endocardialImperfectOstiumPersistence, persistent(congenital)Persistence, persistent(congenital)

About this content

This page is prepared by HealthAssure's clinical team using official coding standards from ICD-10. AI tools assist with drafting explanations, which are then reviewed and verified by healthcare professionals for accuracy. This content is for informational purposes and does not replace professional medical advice. Meet our team.

ICD-10 Code Q21.20 for Atrioventricular septal defect, unspecified as to partial or complete | HealthAssure