Q21.9 Congenital malformation of cardiac septum, unspecified

Billable ICD-10-CM code, FY2026. Exempt from present-on-admission (POA) reporting.

Applicable to

• Septal (heart) defect NOS

Applies from Q21 Congenital malformations of cardiac septa

Excludes1 (never code together)

• acquired cardiac septal defect (I51.0)

MS-DRG index

Defines the logic of DRG(s) 306-307 in MDC 05.

Approximate ICD-9-CM (GEMs)

• 745.9 Unspecified defect of septal closure

Code annotations containing back-references to Q21.9

Back-references to Q21

• Code Also: I27.21 Secondary pulmonary arterial hypertension ("congenital heart disease (Q20-Q28)")
• Type 2 Excludes: P29 Cardiovascular disorders originating in the perinatal period ("congenital malformations of the circulatory system (Q20-Q28)")
• Code Also: Q87.85 MED13L syndrome ("congenital malformations of cardiac septa (Q21.-)")
• Code Also: Z71.87 Encounter for pediatric-to-adult transition counseling ("congenital malformations of the circulatory system (Q20-Q28)")

Diagnosis Index entries for Q21.9

• Anomaly, anomalous (congenital) (unspecified type) › bulbus cordis
• Anomaly, anomalous (congenital) (unspecified type) › cardiac › septal closure
• Anomaly, anomalous (congenital) (unspecified type) › heart › septum
• Defect, defective › septal (heart) NOS
• Deformity › heart (congenital) › septum
• Imperfect › closure (congenital) › septum › heart
• Malformation (congenital) › cardiac › septum

Nearby codes

• 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 (this code)