2026 ICD-10-CM Diagnosis Code I45.81Long QT syndrome

ICD-10-CM Codes›I00–I99›I30-I5A›I45

ICD-10-CM I45.81
CMSSource: CMS FY 2026 ICD-10-CM dataset · Effective Oct 1, 2025 – Sep 30, 2026

I45.81 is a billable ICD-10-CM diagnosis code for long QT syndrome. 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 Conduction disorders.

Code Identity

ICD-10-CM Code
I45.81
Billable Status
Yes — Valid for Submission
Code Describes
Long QT syndrome
Short Description
Long QT syndrome
Same as the full description in the CMS dataset.
Parent Code
I45.8
Other specified conduction disorders

Code Classification

ChapterI00–I99Diseases of the circulatory system
SectionI30-I5AOther forms of heart disease
CategoryI45Other conduction disorders
This CodeI45.81Long QT syndrome

Approximate SynonymsGuidance

Alternate terms and clinical phrases that map to this code.

  • Acquired long QT syndrome
  • Andersen Tawil syndrome
  • Congenital conduction defect
  • Familial long QT syndrome
  • Jervell and Lange-Nielsen syndrome
  • Long QT syndrome
  • Long QT syndrome caused by drug
  • Long QT syndrome type 10
  • Long QT syndrome type 11
  • Long QT syndrome type 12
  • Long QT syndrome type 13
  • Long QT syndrome type 2
  • Long QT syndrome type 3
  • Long QT syndrome type 4
  • Long QT syndrome type 5
  • Long QT syndrome type 6
  • Long QT syndrome type 9
  • Periodic paralysis
  • Prolonged QT interval
  • QT interval - finding
  • Romano-Ward syndrome

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.

    • Jervell-Lange-Nielsen syndrome
    • Long
      • QT syndrome
    • Romano-Ward(prolonged QT interval) syndrome
    • Syndrome
      • Jervell-Lange-Nielsen
    • Syndrome
      • long QT
    • Syndrome
      • QT interval prolongation
    • Syndrome
      • Romano-Ward (prolonged QT interval)

Clinical ClassificationClinical

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

CCSR CIR016
Conduction disorders
Default principal diagnosis: inpatient Yes · outpatient Yes

Clinical InformationClinical

  • Andersen Syndrome

    a form of inherited long qt syndrome (or lqt7) that is characterized by a triad of potassium-sensitive periodic paralysis, ventricular ectopic beats, and abnormal features such as short stature, low-set ears, and scoliosis. it results from mutations of kcnj2 gene which encodes a channel protein (inward rectifier potassium channels) that regulates resting membrane potential.

  • Long QT Syndrome

    a condition that is characterized by episodes of fainting (syncope) and varying degree of ventricular arrhythmia as indicated by the prolonged qt interval. the inherited forms are caused by mutation of genes encoding cardiac ion channel proteins. the two major forms are romano-ward syndrome and jervell-lange nielsen syndrome.

  • 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.

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 I45.81 to ICD-9-CMHistory

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

ICD-9-CM
426.82 Long QT syndrome
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 I45.81Overview

Is I45.81 (Other specified conduction disorders) a billable code?

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

What MS-DRG does I45.81 group to?

When long QT syndrome 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 I45.81?

Under the General Equivalence Mappings, long QT syndrome converts to ICD-9-CM 426.82 (long QT syndrome). 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.