I51.0 Cardiac septal defect, acquired

Billable ICD-10-CM code, FY2026. Acts as a Complication or Comorbidity (CC) as a secondary diagnosis.

Applicable to

• Acquired septal atrial defect (old)
• Acquired septal auricular defect (old)
• Acquired septal ventricular defect (old)

Excludes1 (never code together)

• cardiac septal defect as current complication following acute myocardial infarction (I23.1, I23.2)

Applies from I51 Complications and ill-defined descriptions of heart disease

Excludes2 (not included here)

• heart disease specified as rheumatic (I00-I09)

MS-DRG index

Defines the logic of DRG(s) 314-316 in MDC 05.

Approximate ICD-9-CM (GEMs)

• 429.71 Acquired cardiac septal defect (approximate)

Medicare Code Edits (MCE v43.1 (April 2026))

• Adult diagnoses (age 15 through 124): Age conflict edit. These diagnoses are clinically expected only in patients age 15 through 124.

Code annotations containing back-references to I51.0

Back-references to I51.0

• Type 1 Excludes: I23.1 Atrial septal defect as current complication following acute myocardial infarction ("acquired atrial septal defect not specified as current complication following acute myocardial infarction (I51.0)")
• Type 1 Excludes: I23.2 Ventricular septal defect as current complication following acute myocardial infarction ("acquired ventricular septal defect not specified as current complication following acute myocardial infarction (I51.0)")
• Type 1 Excludes: Q21 Congenital malformations of cardiac septa ("acquired cardiac septal defect (I51.0)")

Diagnosis Index entries for I51.0

• Defect, defective › septal (heart) NOS › acquired (atrial) (auricular) (ventricular) (old)

Nearby codes

• I51 Complications and ill-defined descriptions of heart disease
• I51.0 Cardiac septal defect, acquired (this code)
• I51.1 Rupture of chordae tendineae, not elsewhere classified
• I51.2 Rupture of papillary muscle, not elsewhere classified
• I51.3 Intracardiac thrombosis, not elsewhere classified
• I51.4 Myocarditis, unspecified
• I51.5 Myocardial degeneration