Q21.13 Coronary sinus atrial septal defect

Billable ICD-10-CM code, FY2026. Acts as a Complication or Comorbidity (CC) as a secondary diagnosis. Exempt from present-on-admission (POA) reporting.

Applicable to

• Coronary sinus defect
• Unroofed coronary sinus

Applies from Q21 Congenital malformations of cardiac septa

Excludes1 (never code together)

• acquired cardiac septal defect (I51.0)

Applies from Q21.1 Atrial septal defect

Excludes2 (not included here)

• ostium primum atrial septal defect (type I) (Q21.20)

MS-DRG index

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

Code annotations containing back-references to Q21.13

Back-references to Q21.1

• Code Also: I27.83 Eisenmenger's syndrome ("atrial septal defect (Q21.1-)")

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 Q21.13

• Defect, defective › atrial septal › coronary sinus
• Defect, defective › coronary sinus
• Unroofed coronary sinus

Nearby codes

• Q21.0 Ventricular septal defect
• Q21.1 Atrial septal defect
• Q21.10 Atrial septal defect, unspecified
• Q21.11 Secundum atrial septal defect
• Q21.12 Patent foramen ovale
• Q21.13 Coronary sinus atrial septal defect (this code)
• 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 defect