2026 ICD-10-CM Diagnosis Code I49.01Ventricular fibrillation

ICD-10-CM Codes›I00–I99›I30-I5A›I49

ICD-10-CM I49.01
CMSSource: CMS FY 2026 ICD-10-CM dataset · Effective Oct 1, 2025 – Sep 30, 2026

I49.01 is a billable ICD-10-CM diagnosis code for ventricular fibrillation. 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. Coders also document this condition as idiopathic ventricular fibrillation not Brugada type. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Cardiac arrest and ventricular fibrillation.

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

Code Identity

ICD-10-CM Code
I49.01
Billable Status
Yes — Valid for Submission
Code Describes
Ventricular fibrillation
Short Description
Ventricular fibrillation
Same as the full description in the CMS dataset.
Parent Code
I49.0
Ventricular fibrillation and flutter

Code Classification

ChapterI00–I99Diseases of the circulatory system
SectionI30-I5AOther forms of heart disease
CategoryI49Other cardiac arrhythmias
This CodeI49.01Ventricular fibrillation

Approximate SynonymsGuidance

Alternate terms and clinical phrases that map to this code.

  • Idiopathic ventricular fibrillation not Brugada type
  • Paroxysmal familial ventricular fibrillation
  • Sustained ventricular fibrillation
  • Ventricular fibrillation
  • Ventricular fibrillation and flutter
  • Ventricular flutter
  • Ventricular tachyarrhythmia

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.

    • Fibrillation
      • ventricular

Clinical ClassificationClinical

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

CCSR CIR018
Cardiac arrest and ventricular fibrillation
Default principal diagnosis: inpatient Yes · outpatient Yes

Clinical InformationClinical

  • Romano-Ward Syndrome

    a form of long qt syndrome that is without congenital deafness. it is caused by mutation of the kcnq1 gene which encodes a protein in the voltage-gated potassium channel.

  • Ventricular Fibrillation

    a potentially lethal cardiac arrhythmia that is characterized by uncoordinated extremely rapid firing of electrical impulses (400-600/min) in heart ventricles. such asynchronous ventricular quivering or fibrillation prevents any effective cardiac output and results in unconsciousness (syncope). it is one of the major electrocardiographic patterns seen with cardiac arrest.

  • Ventricular Flutter

    a potentially lethal cardiac arrhythmia characterized by an extremely rapid, hemodynamically unstable ventricular tachycardia (150-300 beats/min) with a large oscillating sine-wave appearance. if untreated, ventricular flutter typically progresses to ventricular fibrillation.

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 I49.01 to ICD-9-CMHistory

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

ICD-9-CM
427.41 Ventricular fibrillation
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 I49.01Overview

Is I49.01 (Ventricular fibrillation and flutter) a billable code?

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

What MS-DRG does I49.01 group to?

When ventricular fibrillation 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 I49.01?

Under the General Equivalence Mappings, ventricular fibrillation converts to ICD-9-CM 427.41 (ventricular fibrillation). The mapping is a direct match.

Footnotes

[1] Not chronic - A diagnosis code that does not fit the criteria for chronic condition (duration, ongoing medical treatment, and limitations) is considered not chronic. Some codes designated as not chronic are acute conditions. Other diagnosis codes that indicate a possible chronic condition, but for which the duration of the illness is not specified in the code description (i.e., we do not know the condition has lasted 12 months or longer) also are considered not chronic.