ICD-10 Code I45.81 – Long QT Syndrome (2026): Diagnosis, Symptoms & Billing Guide
2026 ICD-10-CM Diagnosis Code I45.81 – Long QT syndrome
What it is
Long QT syndrome is a cardiac conduction disorder that prolongs ventricular repolarization on electrocardiogram. It increases the risk of dangerous arrhythmias, especially when the diagnosis is documented by a clinician.
Clinical signs
Patients may have a prolonged QT interval on ECG, syncope, palpitations, or a history of torsades de pointes. Clinical features vary; refer to documentation.
When to use this code
Use I45.81 when the provider documents congenital or acquired long QT syndrome as the diagnosis. It also fits cases where the chart clearly states long QT syndrome with or without symptoms. Check documentation if the record only mentions QT prolongation without a formal syndrome diagnosis.
Do not use for
Do not use this code for isolated ECG QT prolongation when long QT syndrome is not diagnosed. Do not use it for other arrhythmias or nonspecific palpitations without supporting documentation.
Coding tip
Code only when the clinician identifies long QT syndrome, not merely an abnormal ECG finding.