ICD-10 Code I45.3 – Trifascicular block (2026): Diagnosis, Symptoms & Billing Guide
2026 ICD-10-CM Diagnosis Code I45.3 – Trifascicular block
What it is
Trifascicular block is a conduction disorder involving delay or block in all three main fascicles of the heart’s conduction system. It usually reflects advanced His-Purkinje disease and can impair reliable impulse transmission.
Clinical signs
Findings may include PR prolongation with bundle branch block patterns or alternating fascicular abnormalities on ECG. Clinical features vary; refer to documentation.
When to use this code
Use I45.3 when the record specifically documents trifascicular block or clearly describes conduction disease affecting all three fascicles. It may also apply when the provider confirms this diagnosis after ECG interpretation or cardiology review.
Choose this code only when the documentation supports the specific conduction abnormality, not just a nonspecific arrhythmia or isolated bundle branch block. Check documentation if the note is ambiguous.
Do not use for
Do not use this code for isolated first-degree AV block, single bundle branch block, or fascicular block without evidence of trifascicular involvement. Check documentation.
Coding tip
Code I45.3 only when the provider documents the trifascicular diagnosis explicitly or through a clear interpretation of the ECG.