2026 ICD-10-CM Diagnosis Code I31.1Chronic constrictive pericarditis

ICD-10-CM Codes›I00–I99›I30-I5A›I31

ICD-10-CM I31.1
CMSSource: CMS FY 2026 ICD-10-CM dataset · Effective Oct 1, 2025 – Sep 30, 2026

I31.1 is a billable ICD-10-CM diagnosis code for chronic constrictive pericarditis. 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 13 closely related codes. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Pericarditis and pericardial disease.

Code Identity

ICD-10-CM Code
I31.1
Billable Status
Yes — Valid for Submission
Code Describes
Chronic constrictive pericarditis
Short Description
Chronic constrictive pericarditis
Same as the full description in the CMS dataset.
Parent Code
I31
Other diseases of pericardium

Code Classification

ChapterI00–I99Diseases of the circulatory system
SectionI30-I5AOther forms of heart disease
CategoryI31Other diseases of pericardium
This CodeI31.1Chronic constrictive pericarditis

Approximate SynonymsGuidance

Alternate terms and clinical phrases that map to this code.

  • Calcification of pericardium
  • Chronic constrictive pericarditis
  • Chronic pericarditis
  • Constrictive pericarditis
  • Constrictive pericarditis caused by bacteria
  • Constrictive pericarditis caused by virus
  • Effusive constrictive pericarditis
  • Infective constrictive pericarditis
  • Mulibrey nanism syndrome
  • Pericarditis secondary to Mulibrey nanism
  • Subacute constrictive pericarditis
  • Subacute effusive constrictive pericarditis
  • Subacute pericarditis
  • Viral pericarditis

Tabular List NotesGuidance

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

Inclusion Terms

  • Concretio cordis
  • Pericardial calcification

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.

CCSR CIR006
Pericarditis and pericardial disease
Default principal diagnosis: inpatient Yes · outpatient Yes

Clinical InformationClinical

  • Viral Pericarditis

    pericarditis that is caused by an infection with a viral agent.

Patient EducationClinical

Pericardial Disorders

The pericardium is a membrane, or sac, that surrounds your heart. It holds the heart in place and helps it work properly. Problems with the pericardium include:

Read the full article at MedlinePlus

Courtesy of MedlinePlus, a service of the U.S. National Library of Medicine.

Convert I31.1 to ICD-9-CMHistory

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

ICD-9-CM
423.2 Constrictiv pericarditis
Exact Match The mapping is direct, with no qualifiers.

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 I31.1Overview

What is the ICD-10 code for chronic constrictive pericarditis?

The ICD-10-CM code for chronic constrictive pericarditis is I31.1 (sometimes written as I311). It is billable on HIPAA-covered claims from October 1, 2025 through September 30, 2026.

Is I31.1 (Other diseases of pericardium) a billable code?

Yes. This is a billable ICD-10-CM code, specific enough to report chronic constrictive pericarditis on HIPAA-covered claims from October 1, 2025 through September 30, 2026.

What MS-DRG does I31.1 group to?

When chronic constrictive pericarditis 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 I31.1 a CC or MCC?

CMS lists I31.1 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 13 closely related codes in its exclusion list.

What is the ICD-9 equivalent of I31.1?

Under the General Equivalence Mappings, chronic constrictive pericarditis converts to ICD-9-CM 423.2 (constrictiv pericarditis). The mapping is a direct match.