ICD-10 Code I44.5 – Left posterior fascicular block (2026): Diagnosis, Symptoms & Billing Guide
2026 ICD-10-CM Diagnosis Code I44.5 – Left posterior fascicular block
What it is
Left posterior fascicular block is a conduction delay in the posterior fascicle of the left bundle branch. It changes the heart’s electrical pathway and can alter the QRS axis on ECG.
Clinical signs
Clinical features vary; refer to documentation. ECG findings typically show right axis deviation with a normal or slightly widened QRS, in the absence of another cause for the axis shift.
When to use this code
Use I44.5 when the provider documents left posterior fascicular block, left posterior hemiblock, or a confirmed equivalent ECG interpretation. Code it when the finding is current and clinically relevant. Check documentation if the tracing is ambiguous or if another conduction disorder better explains the ECG.
Do not use for
Do not use this code for nonspecific abnormal ECG results without a documented left posterior fascicular block. Do not assign it when the axis deviation is caused by another cardiac or technical factor.
Coding tip
Code from the provider’s final interpretation, not from a machine-read ECG alone.