2027 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 2027 ICD-10-CM dataset · Effective Oct 1, 2026 – Sep 30, 2027

I45.81 is a billable ICD-10-CM diagnosis code for long QT syndrome. It is valid on HIPAA claims for fiscal year 2027 (October 1, 2026 through September 30, 2027) 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

Instructional NotesGuidance

Instructions from the official ICD-10-CM Tabular List that apply to I45.81: its own notes plus those printed at Chapter 9. A note printed at a category, block or chapter applies to every code under it.

Excludes2

Not included here: the excluded condition is not part of this code, but a patient may have both, so both codes may be reported.

From Chapter 9 (I00-I99) Diseases of the circulatory system applies to 1,433 codes
  • certain conditions originating in the perinatal period (P04-P96)
  • certain infectious and parasitic diseases (A00-B99)
  • complications of pregnancy, childbirth and the puerperium (O00-O9A)
  • congenital malformations, deformations, and chromosomal abnormalities (Q00-Q99)
  • endocrine, nutritional and metabolic diseases (E00-E88)
  • injury, poisoning and certain other consequences of external causes (S00-T88)
  • neoplasms (C00-D49)
  • symptoms, signs and abnormal clinical and laboratory findings, not elsewhere classified (R00-R94)
  • systemic connective tissue disorders (M30-M36)
  • transient cerebral ischemic attacks and related syndromes (G45.-)

Source: CMS ICD-10-CM Tabular List. How to read instructional notes.

Referenced in Other NotesGuidance

Instructional notes printed at other codes that name I45.81, its category, or a range that includes it.

Excludes1 1

These codes carry an Excludes1 note naming I45.81: they are not reported together with it, unless the two conditions are unrelated.

  • R94.31 Abnormal electrocardiogram [ECG] [EKG]
    long QT syndrome (I45.81)

Code Also 1

These codes say I45.81 may also be needed to fully describe the condition. The note gives no sequencing direction.

  • I47.21 Torsades de pointes
    if applicable, long QT syndrome (I45.81)

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

Clinical InformationClinical

  • 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.

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 2017–2026No changes
FY 2027CurrentCurrent code set, no changesEffective October 1, 2026 through September 30, 2027.

Questions About I45.81Overview

What is the ICD-10 code for long QT syndrome?

The ICD-10-CM code for long QT syndrome is I45.81 (sometimes written as I4581). It is billable on HIPAA-covered claims from October 1, 2026 through September 30, 2027.

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, 2026 through September 30, 2027.

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 309, 310, 308, with relative weights from 0.5686 to 1.1809 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.