2026 ICD-10-CM Diagnosis Code I49.9Cardiac arrhythmia, unspecified

ICD-10-CM Codes›I00–I99›I30-I5A›I49

ICD-10-CM I49.9
CMSSource: CMS FY 2026 ICD-10-CM dataset · Effective Oct 1, 2025 – Sep 30, 2026

I49.9 is a billable ICD-10-CM diagnosis code for cardiac arrhythmia, unspecified. It is valid on HIPAA claims for fiscal year 2026 (October 1, 2025 through September 30, 2026) and groups to MS-DRG 308 through 310. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Cardiac dysrhythmias.

This medical diagnosis code is frequently used in Cardiology medical specialties to designate conditions such cardiac arrhythmias (other).

Code Identity

ICD-10-CM Code
I49.9
Billable Status
Yes — Valid for Submission
Code Describes
Cardiac arrhythmia, unspecified
Short Description
Cardiac arrhythmia, unspecified
Same as the full description in the CMS dataset.
Parent Code
I49
Other cardiac arrhythmias

Code Classification

ChapterI00–I99Diseases of the circulatory system
SectionI30-I5AOther forms of heart disease
CategoryI49Other cardiac arrhythmias
This CodeI49.9Cardiac arrhythmia, unspecified

Approximate SynonymsGuidance

Alternate terms and clinical phrases that map to this code.

  • Abnormal heart beat
  • Arrhythmia due to and following acute myocardial infarction
  • Arrhythmia due to vegetation of infective endocarditis
  • Atypical Timothy syndrome
  • Cardiac arrhythmia
  • Cardiac arrhythmia associated with genetic disorder
  • Cardiac arrhythmia due to coronary artery spasm
  • Cardiac arrhythmia during pregnancy
  • Cardiac arrhythmia in mother complicating childbirth
  • Cardiac channelopathy
  • EKG: ventricular arrhythmia
  • Fibrillation
  • Finding of regularity of heart rhythm
  • GNB5-related intellectual disability, cardiac arrhythmia syndrome
  • Heart disease in mother complicating childbirth
  • Heart disease in mother complicating pregnancy, childbirth AND/OR puerperium
  • Heart irregularly irregular
  • Heart regularly irregular
  • Irregular heart beat
  • Postoperative cardiac arrhythmia
  • Recurrent metabolic encephalomyopathic crises, rhabdomyolysis, cardiac arrhythmia, intellectual disability syndrome
  • Sudden arrhythmic death syndrome
  • Sudden cardiac death
  • Supraventricular arrhythmia
  • Timothy syndrome
  • Ventricular arrhythmia
  • Withdrawal arrhythmia

Tabular List NotesGuidance

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

Inclusion Terms

  • Arrhythmia (cardiac) NOS

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.

    • Action, heart
      • disorder
    • Action, heart
      • irregular
    • Arrhythmia(auricle)(cardiac)(juvenile)(nodal)(reflex)(supraventricular)(transitory)(ventricle)
    • Disorder(of)
      • heart action
    • Disturbance(s)
      • rhythm, heart
    • Dysrhythmia
      • cardiac
    • Irregular, irregularity
      • action, heart
    • Rhythm
      • disorder
    • Rhythm
      • escape
    • Rhythm
      • heart, abnormal

Clinical ClassificationClinical

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

CCSR CIR017
Cardiac dysrhythmias
Default principal diagnosis: inpatient Yes · outpatient Yes

Patient EducationClinical

Arrhythmia

An arrhythmia is a problem with the rate or rhythm of your heartbeat. Your heart beats too quickly, too slowly, or with an irregular pattern. Changes in the electrical signals that control your heartbeat cause arrhythmias.

The full article covers:

  • What is an arrhythmia?
  • What causes an arrhythmia?
  • What are the symptoms of an arrhythmia?
  • How is an arrhythmia diagnosed?
  • What are the treatments for an arrhythmia?
  • Can arrhythmias be prevented?

Read the full article at MedlinePlus

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

Convert I49.9 to ICD-9-CMHistory

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

ICD-9-CM
427.9 Cardiac dysrhythmia NOS
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 I49.9Overview

Is I49.9 (Other cardiac arrhythmias) a billable code?

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

What MS-DRG does I49.9 group to?

When cardiac arrhythmia, unspecified is the principal diagnosis on an inpatient stay, it groups to MS-DRG 308, 309, 310, with relative weights from 0.5661 to 1.2040 depending on complications. Higher weights mean higher Medicare reimbursement.

What is the ICD-9 equivalent of I49.9?

Under the General Equivalence Mappings, cardiac arrhythmia, unspecified converts to ICD-9-CM 427.9 (cardiac dysrhythmia NOS). The mapping is a direct match.

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.