2026 ICD-10-CM Diagnosis Code I23.1Atrial septal defect as current complication following acute myocardial infarction

ICD-10-CM Codes›I00–I99›I20-I25›STEMI

ICD-10-CM I23.1
CMSSource: CMS FY 2026 ICD-10-CM dataset · Effective Oct 1, 2025 – Sep 30, 2026

I23.1 is a billable ICD-10-CM diagnosis code for atrial septal defect as current complication following acute myocardial infarction. It is valid on HIPAA claims for fiscal year 2026 (October 1, 2025 through September 30, 2026) and groups to MS-DRG 314 through 316. The code is restricted by the Medicare Code Editor to adult patients (age 15 through 124). Coders also document this condition as atrial septal defect due to and following acute myocardial infarction. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Complications of acute myocardial infarction.

This medical diagnosis code is frequently used in Cardiology medical specialties to designate conditions such selected atherosclerosis, ischemia, and infarction.

Code Identity

ICD-10-CM Code
I23.1
Billable Status
Yes — Valid for Submission
Code Describes
Atrial septal defect as current complication following acute myocardial infarction
Short Description
Atrial septal defect as current complication following AMI
Parent Code
I23
Certain current complications following ST elevation (STEMI) and non-ST elevation (NSTEMI) myocardial infarction (within the 28 day period)

Code Classification

ChapterI00–I99Diseases of the circulatory system
SectionI20-I25Ischemic heart diseases
CategorySTEMICertain current complications following ST elevation and non-ST elevation (NSTEMI) myocardial infarction (within the 28 day period) (I23)
This CodeI23.1Atrial septal defect as current complication following acute myocardial infarction

Code EditsBilling

Medicare Code Editor checks that affect claim validity for I23.1.

Adult diagnoses
The Medicare Code Editor detects inconsistencies in adult cases by checking a patient's age and any diagnosis on the patient's record. The adult code edits apply to patients age range is 15–124 years inclusive (e.g., senile delirium, mature cataract).

Approximate SynonymsGuidance

Alternate terms and clinical phrases that map to this code.

  • Atrial septal defect due to and following acute myocardial infarction

Tabular List NotesGuidance

Coding notes and annotation back-references applicable to this code.

Type 1 Excludes

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

Index to Diseases and InjuriesGuidance

Alphabetical index entries that point to this code.

External Cause of Injuries IndexGuidance

References for this code in the External Cause of Injuries Index.

    • 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)

Clinical ClassificationClinical

AHRQ’s CCSR groups this code into broader clinical categories.

CCSR CIR010
Complications of acute myocardial infarction
Default principal diagnosis: inpatient Yes · outpatient Yes

Patient EducationClinical

Heart Attack

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Convert I23.1 to ICD-9-CMHistory

The closest ICD-9-CM equivalents under the General Equivalence Mappings.

ICD-9-CM
429.71 Acq cardiac septl defect
Approximate The match is approximate rather than exact.

Code HistoryHistory

FY 2016AddedAdded to the ICD-10-CM code setEffective October 1, 2015, the first year of ICD-10-CM.
FY 2017–2025No changes
FY 2026CurrentCurrent code set, no changesEffective October 1, 2025 through September 30, 2026.

Questions About I23.1Overview

Is I23.1 a billable code?

Yes. This is a billable ICD-10-CM code, specific enough to report atrial septal defect as current complication following acute myocardial infarction on HIPAA-covered claims from October 1, 2025 through September 30, 2026.

What MS-DRG does I23.1 group to?

When atrial septal defect as current complication following acute myocardial infarction is the principal diagnosis on an inpatient stay, it groups to MS-DRG 314, 315, 316, with relative weights from 0.6821 to 2.0852 depending on complications. Higher weights mean higher Medicare reimbursement.

Who can I23.1 be reported for?

The Medicare Code Editor checks atrial septal defect as current complication following acute myocardial infarction against patient demographics: this code is intended for adult patients (age 15 through 124). Claims outside these limits are flagged as inconsistent.

What is the ICD-9 equivalent of I23.1?

Under the General Equivalence Mappings, atrial septal defect as current complication following acute myocardial infarction converts to ICD-9-CM 429.71 (acq cardiac septl defect). The mapping is approximate, so confirm the match fits the documentation.

Footnotes

[1] Chronic - a chronic condition code indicates a condition lasting 12 months or longer and its effect on the patient based on one or both of the following criteria:

  • The condition results in the need for ongoing intervention with medical products,treatment, services, and special equipment
  • The condition places limitations on self-care, independent living, and social interactions.