2026 ICD-10-CM Diagnosis Code Q20.8Other congenital malformations of cardiac chambers and connections

ICD-10-CM Codes›Q00-Q99›Q20-Q28›Q20

ICD-10-CM Q20.8
CMSSource: CMS FY 2026 ICD-10-CM dataset · Effective Oct 1, 2025 – Sep 30, 2026

Q20.8 is a billable ICD-10-CM diagnosis code for other congenital malformations of cardiac chambers and connections. 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
Q20.8
Billable Status
Yes — Valid for Submission
Code Describes
Other congenital malformations of cardiac chambers and connections
Short Description
Oth congenital malform of cardiac chambers and connections
Parent Code
Q20
Congenital malformations of cardiac chambers and connections

Code Classification

ChapterQ00-Q99Congenital malformations, deformations and chromosomal abnormalities
SectionQ20-Q28Congenital malformations of the circulatory system
CategoryQ20Congenital malformations of cardiac chambers and connections
This CodeQ20.8Other congenital malformations of cardiac chambers and connections

Present on Admission (POA)Billing

Q20.8 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.

  • Abnormal atrial arrangement
  • Abnormal connection of hepatic vein to atrium
  • Abnormal relationship of aortic orifice to pulmonary orifice
  • Abnormal relationship of right ventricle to left ventricle
  • Abnormality of left atrial appendage
  • Abnormality of right atrial appendage
  • Abnormally small cardiac chamber
  • Absent atrioventricular connection with straddling valve
  • Absent left sided atrioventricular connection
  • Absent right sided atrioventricular connection
  • Aortic left ventricular tunnel
  • Aortic tunnel
  • Aortico-left ventricular tunnel of simple type
  • Aortico-left ventricular tunnel with aneurysm of intracardiac septal wall and aneurysm of extracardiac aortic wall
  • Aortico-left ventricular tunnel with extracardiac aneurysm of aortic wall
  • Aortico-left ventricular tunnel with intracardiac aneurysm of septal portion
  • Atresia of mitral valve with absent atrioventricular connection
  • Atrioventricular septal defect - ventricular component under inferior bridging leaflet
  • Atrioventricular septal defect - ventricular component under superior bridging leaflet
  • Atrioventricular septal defect with ventricular component under free floating superior bridging leaflet and chords to papillary muscle at right ventricular free wall
  • Atrioventricular septal defect with ventricular component under inferior bridging leaflet with chords to crest ventricular septum
  • Atrioventricular septal defect with ventricular component under superior bridging leaflet with chords at crest ventricular septum
  • Atrioventricular septal defect with ventricular component under superior bridging leaflet without chordal attachment to ventricular septal crest
  • Atrioventricular septal defect with ventricular imbalance
  • Atrioventricular septal defect with ventricular imbalance consisting of dominant left ventricle and hypoplastic right ventricle
  • Bilateral isomeric atria
  • Bipartite right ventricle
  • Cardiac ventricular dilatation
  • Common atrioventricular valve in functionally univentricular heart
  • Common atrium
  • Concordant atrioventricular connections
  • Concordant ventriculoarterial connection with parallel great arteries
  • Concordant ventriculoarterial connections
  • Congenital abnormality of cardiac ventricle
  • Congenital abnormality of hepatic vein
  • Congenital abnormality of mitral subvalvular apparatus
  • Congenital abnormality of posterior cardiac vein of left ventricle
  • Congenital abnormality of tricuspid leaflet
  • Congenital aneurysm of aorta
  • Congenital aneurysm of heart
  • Congenital aneurysm of subaortic left ventricle
  • Congenital anomaly of left ventricle
  • Congenital atresia of mitral valve
  • Congenital atresia of tricuspid valve
  • Congenital dilatation of aorta
  • Congenital dilatation of atrium
  • Congenital dilatation of cardiac ventricle
  • Congenital hypoplasia of cardiac ventricle
  • Congenital left ventricular aneurysm
  • Congenital left ventricular submitral valve aneurysm
  • Congenital right ventricular aneurysm
  • Congenital right ventricular anomaly
  • Congenital right ventricular diverticulum
  • Cor biloculare
  • Cor triloculare
  • Diffuse hypoplasia of left ventricle
  • Discordant ventriculoarterial connection
  • Divided left atrium with all pulmonary veins to proximal chamber without communication to left atrium
  • Divided left atrium with all pulmonary veins to proximal chamber without communication to left atrium with extracardiac pulmonary venous chamber communication
  • Divided left atrium with restrictive outlet of proximal chamber to left atrium
  • Double outlet from ventricle of indeterminate morphology
  • Dynamic right ventricular outflow tract obstruction
  • Ebstein's anomaly
  • Ebstein's anomaly of tricuspid valve with atrialization of right ventricular chamber
  • Ectasia of left atrial appendage
  • Ectasia of right atrial appendage
  • Functionally univentricular heart
  • Giant right atrium
  • Hepatic vein to left atrium
  • Hepatic vein to left atrium and right atrium
  • Hepatic vein to right atrium
  • Hypoplasia of left ventricular inflow tract
  • Hypoplasia of left ventricular outflow tract
  • Hypoplasia of trabecular portion of right ventricle
  • Indeterminate atrial arrangement
  • Indeterminate ventricular outflow tract obstruction
  • Isolated right ventricular hypoplasia
  • Left atrial appendage - right - juxtaposition
  • Left atrial appendage absent
  • Left hand pattern ventricular topology
  • Left pulmonary artery with absent proximal arterial connection
  • Left sided atrium connecting to both ventricles
  • Left sided atrium connecting to left ventricle
  • Left sided atrium connecting to right ventricle
  • Left sided atrium connecting to ventricle of indeterminate morphology
  • Left ventricular aneurysm
  • Left ventricular hypoplasia
  • Left ventricular outflow tract abnormality
  • Left ventricular outflow tract atresia
  • Left ventricular outflow tract obstruction
  • Left ventricular outflow tract obstruction due to aneurysm of membranous septum
  • Left ventricular outflow tract obstruction due to anterolateral muscle band
  • Left ventricular outflow tract obstruction due to atrioventricular valve
  • Left ventricular outflow tract obstruction due to prolapse of Eustachian valve
  • Left ventricular outflow tract obstruction due to prolapsed arterial valve
  • Left ventricular outflow tract obstruction due to subpulmonary fibromuscular shelf
  • Obstruction of right ventricular outflow tract due to aortico-left ventricular tunnel
  • Parallel course of aorta and pulmonary artery
  • Pulmonary artery with absent proximal arterial connection
  • Right atrial appendage absent
  • Right hand pattern ventricular topology
  • Right sided atrium connecting to both ventricles
  • Right sided atrium connecting to right ventricle
  • Right sided atrium connecting to ventricle of indeterminate morphology
  • Right ventricle anterior to left ventricle
  • Right ventricle inferior to left ventricle
  • Right ventricle posterior to left ventricle
  • Right ventricle superior to left ventricle
  • Right ventricle to left of left ventricle
  • Right ventricular aneurysm
  • Right ventricular diverticulum
  • Right ventricular outflow obstruction - localized
  • Right ventricular outflow tract abnormality
  • Right ventricular outflow tract absent
  • Right ventricular outflow tract atresia
  • Right ventricular outflow tract obstruction
  • Right ventricular outflow tract obstruction due to abnormal cardiac muscle bands
  • Right ventricular outflow tract obstruction due to aneurysm of membranous septum
  • Right ventricular outflow tract obstruction due to atrioventricular valve
  • Right ventricular outflow tract obstruction due to common atrioventricular valve
  • Right ventricular outflow tract obstruction due to fibromuscular shelf
  • Right ventricular outflow tract obstruction due to malaligned outlet septum
  • Right ventricular outflow tract obstruction due to prolapse of Eustachian valve
  • Right ventricular outflow tract obstruction due to prolapsed arterial valve
  • Right ventricular outflow tract obstruction due to septal hypertrophy
  • Right ventricular outflow tract obstruction due to septoparietal trabeculation
  • Single inlet ventricle with absent atrioventricular connection
  • Single outlet ventriculoarterial connection
  • Single ventricular outlet above right ventricle
  • Solitary ventricle of indeterminate morphology
  • Subaortic stenosis due to restrictive ventricular septal defect in functionally univentricular heart
  • Superior to inferior ventricular relationship
  • Supramitral left atrial ring
  • Thoracodidymus
  • Thoracopagus
  • Thoracopagus with conjoined atria
  • Thoracopagus with conjoined atria and ventricles
  • Transposition of great arteries with concordant atrioventricular connections and ventricular septal defect and left ventricular outflow tract obstruction
  • Tricuspid atresia with absent right atrioventricular connection
  • Tripartite right ventricle
  • Two chambered right ventricle
  • Uniatrial biventricular connection with absent left sided atrioventricular connection with straddling valve
  • Uniatrial biventricular connection with absent right sided atrioventricular connection with straddling valve
  • Unipartite right ventricle
  • Univentricular atrioventricular connection with absent left sided atrioventricular connection
  • Univentricular atrioventricular connection with absent right sided atrioventricular connection
  • Ventricular imbalance
  • Ventricular imbalance with dominant right ventricle and hypoplastic left ventricle

Tabular List NotesGuidance

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

Inclusion Terms

  • Cor binoculare

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.

    • Anomaly, anomalous(congenital) (unspecified type)
      • atrial
        • bands or folds
    • Anomaly, anomalous(congenital) (unspecified type)
      • auricle
        • heart
    • Anomaly, anomalous(congenital) (unspecified type)
      • band
        • atrial
    • Anomaly, anomalous(congenital) (unspecified type)
      • cardiac
        • chambers
          • specified NEC
    • Anomaly, anomalous(congenital) (unspecified type)
      • heart
        • auricle
    • Anomaly, anomalous(congenital) (unspecified type)
      • heart
        • ventricle
    • Cor
      • biloculare
    • Cor
      • triloculare
    • Double
      • auricle (heart)
    • Malformation(congenital)
      • cardiac
        • chambers
          • specified type NEC
    • Unilocular heart

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

Clinical InformationClinical

  • Discordant Ventriculoarterial Connection

    a rare congenital cardiovascular abnormality in which the aorta arises from the right ventricle and the pulmonary artery arises from the left ventricle.

  • Cor Triloculare

    a congenital anatomic anomaly in which the heart has only three chambers.

  • Left Ventricular Outflow Tract Obstruction

    obstruction of the left ventricular outflow tract. it is caused by aortic valve, supravalvar, or subvalvar defects.

  • Left Ventricular Aneurysm

    a bulge or ballooning in the wall of the left ventricle of the heart.

  • Cor Biloculare

    a congenital anatomic anomaly in which the heart has only two chambers.

  • Thoracodidymus

    conjoined twins united at the thorax.

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.

Convert Q20.8 to ICD-9-CMHistory

The closest ICD-9-CM equivalents under the General Equivalence Mappings.

ICD-9-CM
745.19 Transpos great vess NEC
Approximate The match is approximate rather than exact.
ICD-9-CM
745.7 Cor biloculare
Approximate The match is approximate rather than exact.
ICD-9-CM
745.8 Septal closure anom NEC
Approximate The match is approximate rather than exact.

Code HistoryHistory

FY 2016AddedAdded to the ICD-10-CM code setEffective October 1, 2015, the first year of ICD-10-CM.
FY 2017–2025No changes
FY 2026CurrentCurrent code set, no changesEffective October 1, 2025 through September 30, 2026.

Questions About Q20.8Overview

Is Q20.8 (Congenital malformations of cardiac chambers and connections) a billable code?

Yes. This is a billable ICD-10-CM code, specific enough to report other congenital malformations of cardiac chambers and connections on HIPAA-covered claims from October 1, 2025 through September 30, 2026.

What MS-DRG does Q20.8 group to?

When other congenital malformations of cardiac chambers and connections 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 Q20.8 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 other congenital malformations of cardiac chambers and connections on inpatient claims.

What is the ICD-9 equivalent of Q20.8?

Under the General Equivalence Mappings, other congenital malformations of cardiac chambers and connections converts to ICD-9-CM 745.19 (transpos great vess NEC), 745.7 (cor biloculare), and 745.8 (septal closure anom NEC). The mapping is approximate, so confirm the match fits the documentation.

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.