I23.1 Atrial septal defect as current complication following acute myocardial infarction

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

Excludes1 (never code together)

• acquired atrial septal defect not specified as current complication following acute myocardial infarction (I51.0)

Risk adjustment (HCC)

• CMS-HCC V28: HCC 229 — Unstable Angina and Other Acute Ischemic Heart Disease
• CMS-HCC V22: HCC 87 — Unstable Angina and Other Acute Ischemic Heart Disease
• RxHCC V08: HCC 188 — Coronary Artery Disease
• ESRD V24: HCC 87

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 I23.1

Back-references to I23.1

• Type 1 Excludes: I51.0 Cardiac septal defect, acquired ("cardiac septal defect as current complication following acute myocardial infarction (I23.1, I23.2)")

Back-references to I23

• Type 2 Excludes: I74 Arterial embolism and thrombosis ("coronary embolism and thrombosis (I21-I25)")
• Type 2 Excludes: I82 Other venous embolism and thrombosis ("coronary (I21-I25)")

Diagnosis Index entries for I23.1

• Complication (s) (from) (of) › following › acute myocardial infarction NEC › atrial › septal defect
• Complication (s) (from) (of) › following › acute myocardial infarction NEC › defect › septal › atrial (heart)
• Defect, defective › atrial septal › following acute myocardial infarction (current complication)
• Defect, defective › septal (heart) NOS › atrial › following acute myocardial infarction (current complication)

Nearby codes

• I23 Certain current complications following ST elevation (STEMI) and non-ST elevation (NSTEMI) myocardial infarction (within the 28 day period)
• I23.0 Hemopericardium as current complication following acute myocardial infarction
• I23.1 Atrial septal defect as current complication following acute myocardial infarction (this code)
• I23.2 Ventricular septal defect as current complication following acute myocardial infarction
• I23.3 Rupture of cardiac wall without hemopericardium as current complication following acute myocardial infarction
• I23.4 Rupture of chordae tendineae as current complication following acute myocardial infarction
• I23.5 Rupture of papillary muscle as current complication following acute myocardial infarction
• I23.6 Thrombosis of atrium, auricular appendage, and ventricle as current complications following acute myocardial infarction