2027 ICD-10-CM Diagnosis Code I45.3Trifascicular block

ICD-10-CM Codes›I00–I99›I30-I5A›I45

ICD-10-CM I45.3
CMSSource: CMS FY 2027 ICD-10-CM dataset · Effective Oct 1, 2026 – Sep 30, 2027

I45.3 is a billable ICD-10-CM diagnosis code for trifascicular block. 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, 791, 793. As a secondary diagnosis, it counts as a complication or comorbidity (CC) and moves an inpatient stay to a higher severity level within its MS-DRG family. It does not count, however, when the principal diagnosis is one of 54 closely related codes. Coders also document this condition as right bundle branch block with left bundle branch block. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Conduction disorders.

Code Identity

ICD-10-CM Code
I45.3
Billable Status
Yes — Valid for Submission
Code Describes
Trifascicular block
Short Description
Trifascicular block
Same as the full description in the CMS dataset.
Parent Code
I45
Other conduction disorders

Code Classification

ChapterI00–I99Diseases of the circulatory system
SectionI30-I5AOther forms of heart disease
CategoryI45Other conduction disorders
This CodeI45.3Trifascicular block

Approximate SynonymsGuidance

Alternate terms and clinical phrases that map to this code.

  • Right bundle branch block with left bundle branch block
  • Trifascicular block
  • Trifascicular block on electrocardiogram

Instructional NotesGuidance

Instructions from the official ICD-10-CM Tabular List that apply to I45.3: 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.

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

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 I45.3 to ICD-9-CMHistory

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

ICD-9-CM
426.54 Trifascicular block
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 I45.3Overview

What is the ICD-10 code for trifascicular block?

The ICD-10-CM code for trifascicular block is I45.3 (sometimes written as I453). It is billable on HIPAA-covered claims from October 1, 2026 through September 30, 2027.

Is I45.3 (Other conduction disorders) a billable code?

Yes. This is a billable ICD-10-CM code, specific enough to report trifascicular block on HIPAA-covered claims from October 1, 2026 through September 30, 2027.

What MS-DRG does I45.3 group to?

When trifascicular block is the principal diagnosis on an inpatient stay, it groups to MS-DRG 793, 791, 309, 310, 308, with relative weights from 0.5686 to 4.2192 depending on complications. Higher weights mean higher Medicare reimbursement.

Is I45.3 a CC or MCC?

CMS lists I45.3 as a CC (complication or comorbidity) for FY 2027. Reported as a secondary diagnosis, it moves the inpatient stay to a higher-weighted DRG within its severity family. It does not count when the principal diagnosis is one of the 54 closely related codes in its exclusion list.

What is the ICD-9 equivalent of I45.3?

Under the General Equivalence Mappings, trifascicular block converts to ICD-9-CM 426.54 (trifascicular block). The mapping is a direct match.