2027 ICD-10-CM Diagnosis Code Q21Congenital malformations of cardiac septa

ICD-10-CM Codes›Q00-Q99›Q20-Q28›Q21

ICD-10-CM Q21
CMSSource: CMS FY 2027 ICD-10-CM dataset · Effective Oct 1, 2026 – Sep 30, 2027

Q21 is a non-billable ICD-10-CM category code for congenital malformations of cardiac septa, so it cannot be submitted on claims. Use a more specific code from this category instead, such as Q21.0, Q21.10, Q21.11, and Q21.12.

Code Identity

ICD-10-CM Code
Q21
Billable Status
No — Non-Billable Category
Code Describes
Congenital malformations of cardiac septa
Short Description
Congenital malformations of cardiac septa
Same as the full description in the CMS dataset.
Chapter
Q20-Q28
Congenital malformations of the circulatory system

Code Classification

ChapterQ00-Q99Congenital malformations, deformations and chromosomal abnormalities
SectionQ20-Q28Congenital malformations of the circulatory system
CategoryQ21Congenital malformations of cardiac septa
This CodeQ21Congenital malformations of cardiac septa

Specific Coding for Congenital malformations of cardiac septaOverview

Non-specific codes like Q21 require more characters. Use one of these billable codes instead:

  • Use Q21.0 for Ventricular septal defect

  • Q21.1 for Atrial septal defect

  • Use Q21.10 for Atrial septal defect, unspecified

  • Use Q21.11 for Secundum atrial septal defect

  • Use Q21.12 for Patent foramen ovale

  • Use Q21.13 for Coronary sinus atrial septal defect

  • Use Q21.14 for Superior sinus venosus atrial septal defect

  • Use Q21.15 for Inferior sinus venosus atrial septal defect

  • Use Q21.16 for Sinus venosus atrial septal defect, unspecified

  • Use Q21.19 for Other specified atrial septal defect

  • Q21.2 for Atrioventricular septal defect

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

  • Use Q21.21 for Partial atrioventricular septal defect

  • Use Q21.22 for Transitional atrioventricular septal defect

  • Use Q21.23 for Complete atrioventricular septal defect

  • Use Q21.3 for Tetralogy of Fallot

  • Use Q21.4 for Aortopulmonary septal defect

  • Use Q21.8 for Other congenital malformations of cardiac septa

  • Use Q21.9 for Congenital malformation of cardiac septum, unspecified

Instructional NotesGuidance

Instructions from the official ICD-10-CM Tabular List that apply to Q21: its own notes plus those printed at Chapter 17. A note printed at a category, block or chapter applies to every code under it.

Excludes1

Not coded here: the excluded code is never reported together with this one, unless the two conditions are unrelated.

  • acquired cardiac septal defect (I51.0)

Excludes2

Not included here: the excluded condition is not part of this code, but a patient may have both, so both codes may be reported.

From Chapter 17 (Q00-QA1) Congenital malformations, deformations and chromosomal abnormalities applies to 900 codes
  • inborn errors of metabolism (E70-E88)

Notes

General instructions on how these codes are used.

From Chapter 17 (Q00-QA1) Congenital malformations, deformations and chromosomal abnormalities applies to 900 codes
  • Codes from this chapter are not for use on maternal records

Source: CMS ICD-10-CM Tabular List. How to read instructional notes.

Referenced in Other NotesGuidance

Instructional notes printed at other codes that name Q21, its category, or a range that includes it.

Use Additional Code 1

These codes say to use an additional code from the note, and Q21 is one of the codes named.

  • Q87.88 CTNNB1 syndrome
    congenital heart malformations (Q20.0-Q24.9) names Q20.0-Q24.9, which includes this code

Code Also 1

These codes say Q21 may also be needed to fully describe the condition. The note gives no sequencing direction.

  • Q87.85 MED13L syndrome
    congenital malformations of cardiac septa (Q21.-)

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 HistoryHistory

FY 2016AddedAdded to the ICD-10-CM code setEffective October 1, 2015, the first year of ICD-10-CM.
FY 2017–2026No changes
FY 2027CurrentCurrent code set, no changesEffective October 1, 2026 through September 30, 2027.

Questions About Q21Overview

What is the ICD-10 code for congenital malformations of cardiac septa?

Q21 is the ICD-10-CM category for congenital malformations of cardiac septa, but it is a non-billable header: claims need a more specific code from this category, listed on this page.

Is Q21 (Congenital malformations of cardiac septa) a billable code?

No. This is a category header that groups the codes for congenital malformations of cardiac septa, and headers cannot be submitted on claims. Claims for congenital malformations of cardiac septa need a more specific code from this category, such as Q21.0, Q21.10, and Q21.11.

Can Q21 be reported with I51.0?

Not as a rule. The Excludes1 note on Q21 lists "acquired cardiac septal defect (I51.0)". An Excludes1 note means the excluded code is never reported together with this one; the only exception is when the two conditions are unrelated to each other (Official Guidelines, Section I.A.12.a).