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I45.81 ICD-10-CM Code: Long QT syndrome

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Billing Status: YES. This is a valid, specific, and billable ICD-10-CM reference.

Billable · FY2027A valid, specific ICD-10-CM code, reportable for dates of service in FY2027.

What you need to know

Source: CMS/NCHS Official ICD-10-CM tabular notes, quoted. From the CMS/NCHS tabular list for the release in force. A note the category or block publishes applies to this code too; the Instructions section marks which is which.

The tabular list publishes no instructional note for this code itself.

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Inpatient Payment Groups (MS-DRG)

Potential MS-DRG participation — not a DRG assignment.

MS-DRGs this diagnosis helps define, as principal or secondary, per the CMS ICD-10-CM/PCS MS-DRG Definitions Manual v44, Appendix B.

  • MS-DRG 308 — CARDIAC ARRHYTHMIA AND CONDUCTION DISORDERS WITH MCC (MDC 05)
  • MS-DRG 309 — CARDIAC ARRHYTHMIA AND CONDUCTION DISORDERS WITH CC (MDC 05)
  • MS-DRG 310 — CARDIAC ARRHYTHMIA AND CONDUCTION DISORDERS WITHOUT CC/MCC (MDC 05)

A diagnosis appearing in a group's logic does not by itself determine the DRG assigned to a stay; the grouper uses the full claim.

Coding context

Guidelines, coding notes, decision aids, relationships (with MS-DRG and CCSR classification), hierarchy, HCC, coverage and the context map: what a coder reaches for after the core. Each section names whether it is official source data, a MedCoder-derived relationship or MedCoder editorial.

Code Overview

Long QT syndrome is a billable ICD-10-CM diagnosis code (I45.81).

MedCoder summary Summary composed by MedCoder from this code's official ICD-10-CM record. The tabular instructional notes themselves appear verbatim below.

Verify Before Coding

  • No Medicare Code Editor or MS-DRG Definitions Manual restrictions apply to this code.

From the code registry, the Medicare Code Editor, and the MS-DRG Definitions Manual. Check it against a full claim in Claim Check.

Relationships & Classification

MedCoder-derived relationships — computed from published CMS and AHRQ datasets

Other codes that name I45.81 or its code family, from the CMS ICD-10-CM tabular instructional notes. Tabular-note edges are stored at the code family level that carries each note.

Referenced by 1 Excludes1 note: R94.31 — Abnormal electrocardiogram [ECG] [EKG].

These codes’ tabular lists mark this diagnosis as mutually exclusive — not reported together unless the conditions are documented as unrelated.

Referenced by 1 Code Also instruction: I47.21 — Torsades de pointes.

These codes suggest coding this condition alongside when both are present.

MS-DRG Grouper Relationships (FY2027)

Potential MS-DRG participation — not a DRG assignment.

FY2027 MS-DRG: not on the CMS CC/MCC list — as a secondary diagnosis this code does not change MS-DRG severity for that release.

Named in the grouper logic of 3 MS-DRGs: DRG 308 (MDC 05), DRG 309 (MDC 05), DRG 310 (MDC 05).

From the CMS MS-DRG Definitions Manual (Appendices B and C). Actual DRG assignment depends on the complete claim.

Clinical classification (AHRQ CCSR):CIR016 — Conduction disorders (default).

Clinical Classifications Software Refined (CCSR) for ICD-10-CM Diagnoses. Healthcare Cost and Utilization Project (HCUP), Agency for Healthcare Research and Quality.

Related Codes

Same clinical category (CCSR)

AHRQ's Clinical Classifications Software groups these diagnoses under the same clinical category (Conduction disorders).

I44.30 — Unspecified atrioventricular block, I44.39 — Other atrioventricular block, I44.4 — Left anterior fascicular block, I44.5 — Left posterior fascicular block, I44.60 — Unspecified fascicular block, I44.69 — Other fascicular block, I44.7 — Left bundle-branch block, unspecified, I45.0 — Right fascicular block, I45.10 — Unspecified right bundle-branch block, I45.19 — Other right bundle-branch block, I45.2 — Bifascicular block, I45.3 — Trifascicular block, I45.4 — Nonspecific intraventricular block, I45.5 — Other specified heart block, I45.6 — Pre-excitation syndrome, I45.89 — Other specified conduction disorders, I45.9 — Conduction disorder, unspecified, Z45.010 — Encounter for checking and testing of cardiac pacemaker pulse generator [battery], Z45.018 — Encounter for adjustment and management of other part of cardiac pacemaker, Z95.0 — Presence of cardiac pacemaker, +3 more

Same Index main term, other category

The ICD-10-CM Index to Diseases and Injuries files this code under the main term “Long”; these codes share that main term but sit in a different category of the Tabular List.

O63.0 — Prolonged first stage (of labor) (labor, first stage), O63.1 — Prolonged second stage (of labor) (labor, second stage), O63.9 — Long labor, unspecified (labor), U09.9 — Post COVID-19 condition, unspecified (COVID)

Contextual Map

Every relationship of I45.81 in one view: hierarchy, official tabular instructions in both directions, clinical classification, risk adjustment, MS-DRG participation, index terms and change history — each edge carrying the CMS source it derives from.

Run I45.81 with these 2 related codes in Claim Check

Hierarchy

Referenced by Excludes1 notes

Referenced by Code Also instructions

  • I47.21 — Torsades de pointes[Code Also]: “, if applicable, long QT syndrome (I45.81)”— CMS ICD-10-CM tabular instructional notes · icd10cm-fy2027

Clinical classification (CCSR)

MS-DRG Grouper

MDC crossing

  • MDC 05 — Diseases and Disorders of the Circulatory System[MDC crossing]: “Diseases and Disorders of the Circulatory System — the grouper's crossing between diagnoses and procedures: a principal diagnosis sets the MDC, and same-MDC procedures move the stay to its surgical DRGs. 15,708 same-MDC procedures group here; browse them on the MDC page.”— CMS MS-DRG Definitions Manual · FY2027

Index entries

  • Jervell-Lange-Nielsen syndrome[Index term]— CMS ICD-10-CM Index to Diseases and Injuries · icd10cm-fy2027
  • Long, QT syndrome[Index term]— CMS ICD-10-CM Index to Diseases and Injuries · icd10cm-fy2027
  • Romano-Wardsyndrome (prolonged QT interval)[Index term]— CMS ICD-10-CM Index to Diseases and Injuries · icd10cm-fy2027
  • Syndrome, Jervell-Lange-Nielsen[Index term]— CMS ICD-10-CM Index to Diseases and Injuries · icd10cm-fy2027
  • Syndrome, long QT[Index term]— CMS ICD-10-CM Index to Diseases and Injuries · icd10cm-fy2027
  • Syndrome, QT interval prolongation[Index term]— CMS ICD-10-CM Index to Diseases and Injuries · icd10cm-fy2027
  • Syndrome, Romano-Ward (prolonged QT interval)[Index term]— CMS ICD-10-CM Index to Diseases and Injuries · icd10cm-fy2027

Nearest codes (13)

Change history

  • FY2016 — In the code set at ICD-10-CM adoption [Change history]— CMS release files (code change ledger) · icd10cm-fy2016

Reference

Index terms and tables, published questions and FAQ, every source behind this page with its release and checksum, the date-of-service check and the complete change history.

Indexed Clinical Terms (7)

Official source data — entries quoted as published, in the Index’s own lookup phrasing

Clinical term phrases from the official ICD-10-CM Index to Diseases and Injuries that map to this code. These are alphabetic-index entries shown as the Index writes them — lookup phrasing, not necessarily the wording of a final diagnosis.

Sources for this page

Codes, titles, notes, index terms and mappings on this page are transcribed from the datasets below. Relationships MedCoder computed and text MedCoder wrote are labelled where they appear.

Code, title, tabular notes and index terms Official source data
CMS/CDC ICD-10-CM FY2027 tabular list, index and tables, effective October 1, 2026 Release, file and checksum · Publisher’s page
Claim edits Official source data
CMS Definitions of Medicare Code Edits — v44.0 (October 2026) Release, file and checksum · Publisher’s page
Inpatient payment groups Official source data
CMS MS-DRG Definitions Manual (incl. Appendix B diagnosis index, Appendix C CC/MCC list, Appendix E procedure index) and IPPS Final Rule tables — v44 Release, file and checksum · Publisher’s page
Change history and date-of-service validity Official source data
CMS ICD-10-CM release addenda, ingested release by release into the change ledger Release, file and checksum · Publisher’s page
Comparisons, relationships and the contextual map MedCoder-derived relationship
Computed by MedCoder from the tabular notes and tables above; every derived relationship is marked as derived where it appears
Summary and FAQ answers MedCoder editorial explanation
Written by MedCoder to explain the sources above: drafted with AI assistance, checked by a person against the release files, and labelled as MedCoder text where it appears. Not official text.

Current data releases:ICD-10-CM FY2027 · ICD-10-PCS FY2027 · HCPCS October 2026 · MS-DRG v44 · Medicare Code Editor v44.0 · NCCI PTP Q4 2026 · MUE Q4 2026 · NCD code lists 2026-01 · LCD export September 20, 2026 · All releases and sources

Labels on this page: Official source data · MedCoder-derived relationship · MedCoder editorial explanation. How to read the labels · All data sources and release dates · CMS coding rules

Cite this page

Reference this page in a research guide, syllabus or article. The release is included because code content changes each year.

MedCoder.ai. "I45.81 — Long QT syndrome." ICD-10-CM FY2027. https://medcoder.ai/icd10/code/i45.81-long-qt-syndrome

Change history

  • FY2016 — October 1, 2015
    In the code set at ICD-10-CM adoption
    Long QT syndrome

No changes since FY2016 — additions, deletions, description changes and billable-status changes are tracked through FY2027, and none are recorded for this code. Note changes are tracked from FY2027 only.

Nearest Codes in This Family

Official ICD-10-CM classifications closest to I45.81 in its code family, with their registry titles.

View all codes in the I45 family