2026 ICD-10-CM Diagnosis Code I51.0Cardiac septal defect, acquired
ICD-10-CM Codes›I00–I99›I30-I5A›I51
- Billable — Valid for Submission
- CC — Complication or Comorbidity
- Chronic Condition
I51.0 is a billable ICD-10-CM diagnosis code for cardiac septal defect, acquired. 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. As a secondary diagnosis, it counts as a complication or comorbidity (CC) and moves an inpatient stay to a higher severity level within its MS-DRG family. It does not count, however, when the principal diagnosis is one of 115 closely related codes. The code is restricted by the Medicare Code Editor to adult patients (age 15 through 124). In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Other and ill-defined heart disease.
Code Identity
Code Classification
Code EditsBilling
Medicare Code Editor checks that affect claim validity for I51.0.
Approximate SynonymsGuidance
Alternate terms and clinical phrases that map to this code.
- Acquired abnormality of atrium
- Acquired atrial septal defect
- Acquired atrioventricular fistula of heart
- Acquired atrioventricular septal defect
- Acquired cardiac septal defect
- Acquired interatrial communication
- Acquired ventricular septal defect
- Bidirectional cardiac shunt
- Bidirectional cardiovascular shunt
- Cardiac shunt
- Cardiovascular shunt finding
- Enlarged septal foramen of heart
- Left to right cardiac shunt
- Left to right cardiovascular shunt
- Recurrent atrial component of atrioventricular septal defect after prior cardiovascular surgical procedure
- Recurrent interatrial communication after prior cardiovascular surgical procedure
- Recurrent interatrial communication following procedure
- Recurrent ventricular component of atrioventricular septal defect after prior cardiovascular surgical procedure
- Recurrent ventricular septal defect following procedure
- Residual interatrial communication following procedure
- Residual ventricular septal defect following procedure
- Restrictive ventricular septal defect
- Right to left cardiac shunt
- Right to left cardiovascular shunt
- Surgically constructed interatrial communication
- Traumatic interventricular septal defect
- Ventricular septal defect due to and following infective endocarditis
- Ventricular septal defect following procedure
Tabular List NotesGuidance
Coding notes and annotation back-references applicable to this code.
Inclusion Terms
- Acquired septal atrial defect (old)
- Acquired septal auricular defect (old)
- Acquired septal ventricular defect (old)
Type 1 Excludes
These terms are the conditions for which that code is to be used. The terms may be synonyms of the code title, or, in the case of "other specified" codes, the terms are a list of the various conditions assigned to that code. The inclusion terms are not necessarily exhaustive. Additional terms found only in the Alphabetic Index may also be assigned to a code.
A type 1 excludes note is a pure excludes note. It means "NOT CODED HERE!" An Excludes1 note indicates that the code excluded should never be used at the same time as the code above the Excludes1 note. An Excludes1 is used when two conditions cannot occur together, such as a congenital form versus an acquired form of the same condition.
Index to Diseases and InjuriesGuidance
Alphabetical index entries that point to this code.
Clinical ClassificationClinical
AHRQ’s CCSR groups this code into broader clinical categories.
Patient EducationClinical
Heart Diseases
Heart disease is a general term that includes many types of heart problems. It's a type of cardiovascular disease, which means heart and blood vessel disease.
The full article covers:
- What is heart disease?
- What are the types of heart disease?
- What causes heart diseases?
- Who is more likely to develop heart diseases?
- What are the symptoms of heart disease?
- How are heart diseases diagnosed?
- What are the treatments for heart disease?
- Can heart diseases be prevented?
Read the full article at MedlinePlus
Courtesy of MedlinePlus, a service of the U.S. National Library of Medicine.
Convert I51.0 to ICD-9-CMHistory
The closest ICD-9-CM equivalents under the General Equivalence Mappings.
Code HistoryHistory
Questions About I51.0Overview
What is the ICD-10 code for cardiac septal defect, acquired?
The ICD-10-CM code for cardiac septal defect, acquired is I51.0 (sometimes written as I510). It is billable on HIPAA-covered claims from October 1, 2025 through September 30, 2026.
Is I51.0 (Complications and ill-defined descriptions of heart disease) a billable code?
Yes. This is a billable ICD-10-CM code, specific enough to report cardiac septal defect, acquired on HIPAA-covered claims from October 1, 2025 through September 30, 2026.
What MS-DRG does I51.0 group to?
When cardiac septal defect, acquired 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.
Is I51.0 a CC or MCC?
CMS lists I51.0 as a CC (complication or comorbidity) for FY 2026. Reported as a secondary diagnosis, it moves the inpatient stay to a higher-weighted DRG within its severity family. It does not count when the principal diagnosis is one of the 115 closely related codes in its exclusion list.
Who can I51.0 be reported for?
The Medicare Code Editor checks cardiac septal defect, acquired against patient demographics: this code is intended for adult patients (age 15 through 124). Claims outside these limits are flagged as inconsistent.
