Congenital malformations of cardiac septa (Q21) ICD-10-CM
The Q21 code range covers congenital malformations of cardiac septa with 20 ICD-10-CM diagnosis codes. 17 of them are billable and valid for claim submission in fiscal year 2027, and the category headers group them but cannot themselves be billed.
Type 1 Excludes
A type 1 excludes note is a pure excludes note. It means "NOT CODED HERE!" An Excludes1 note indicates that the code excluded should never be used at the same time as the code above the Excludes1 note. An Excludes1 is used when two conditions cannot occur together, such as a congenital form versus an acquired form of the same condition.
- acquired cardiac septal defect I51.0
Codes in the Q21 Range 20 codes · 17 billable
- Q21 Congenital malformations of cardiac septaNon-billable
- Q21.0 Ventricular septal defect
- Q21.1 Atrial septal defectNon-billable
- Q21.10 Atrial septal defect, unspecified
- Q21.11 Secundum atrial septal defect
- Q21.12 Patent foramen ovale
- Q21.13 Coronary sinus atrial septal defect
- Q21.14 Superior sinus venosus atrial septal defect
- Q21.15 Inferior sinus venosus atrial septal defect
- Q21.16 Sinus venosus atrial septal defect, unspecified
- Q21.19 Other specified atrial septal defect
- Q21.2 Atrioventricular septal defectNon-billable
- Q21.20 Atrioventricular septal defect, unspecified as to partial or complete
- Q21.21 Partial atrioventricular septal defect
- Q21.22 Transitional atrioventricular septal defect
- Q21.23 Complete atrioventricular septal defect
- Q21.3 Tetralogy of Fallot
- Q21.4 Aortopulmonary septal defect
- Q21.8 Other congenital malformations of cardiac septa
- Q21.9 Congenital malformation of cardiac septum, unspecified
Clinical Terms in This Code Range
Definitions from the National Library of Medicine for conditions coded in the Q21 range.
Aortopulmonary Septal Defect
A developmental abnormality in which the spiral (aortopulmonary) septum failed to completely divide the TRUNCUS ARTERIOSUS into ASCENDING AORTA and PULMONARY ARTERY. This abnormal communication between the two major vessels usually lies above their respective valves (AORTIC VALVE; PULMONARY VALVE).
Atrioventricular Septal Defect
A congenital heart malformation characterized by abnormalities in the anatomic structures that relate to the endocardial cushions. These abnormalities can include defects in the lower part of the atrial septum and the ventricular septum and lack of separation of the mitral and tricuspid valves.
Foramen Ovale, Patent
A condition in which the FORAMEN OVALE in the ATRIAL SEPTUM fails to close shortly after birth. This results in abnormal communications between the two upper chambers of the heart. An isolated patent ovale foramen without other structural heart defects is usually of no hemodynamic significance.
Heart Septal Defects, Atrial
Developmental abnormalities in any portion of the ATRIAL SEPTUM resulting in abnormal communications between the two upper chambers of the heart. Classification of atrial septal defects is based on location of the communication and types of incomplete fusion of atrial septa with the ENDOCARDIAL CUSHIONS in the fetal heart. They include ostium primum, ostium secundum, sinus venosus, and coronary sinus defects.
Heart Septal Defects, Ventricular
Developmental abnormalities in any portion of the VENTRICULAR SEPTUM resulting in abnormal communications between the two lower chambers of the heart. Classification of ventricular septal defects is based on location of the communication, such as perimembranous, inlet, outlet (infundibular), central muscular, marginal muscular, or apical muscular defect.
Tetralogy of Fallot
A combination of congenital heart defects consisting of four key features including VENTRICULAR SEPTAL DEFECTS; PULMONARY STENOSIS; RIGHT VENTRICULAR HYPERTROPHY; and a dextro-positioned AORTA. In this condition, blood from both ventricles (oxygen-rich and oxygen-poor) is pumped into the body often causing CYANOSIS.
About the Q21 Code Range
These heart malformations are present at birth. Most involve septa, the walls that separate parts of the heart.
The categories distinguish ventricular septal defects (Q21.0), atrial septal defects (Q21.1), and atrioventricular septal defects (Q21.2). Atrial defects divide by named type, including patent foramen ovale and sinus venosus defects. Atrioventricular defects divide into partial, transitional, complete, or unspecified forms.
Separate codes identify tetralogy of Fallot (Q21.3) and aortopulmonary septal defect (Q21.4). The category also has codes for other congenital malformations of cardiac septa (Q21.8) and an unspecified congenital malformation of the cardiac septum (Q21.9).
Questions About This Page
How many billable codes are in the Q21 range?
Of the 20 codes in this range, 17 are billable and valid for claim submission from October 1, 2026 through September 30, 2027. Category header codes group them but cannot be reported on claims.
What does the Q21 range classify?
The range classifies congenital malformations of cardiac septa. Each code links to its own reference page with billing status, MS-DRG grouping, coding notes, and clinical information.
Related References
Source: CMS FY 2027 ICD-10-CM Tabular List and order file, effective October 1, 2026 through September 30, 2027.
