ICD-10 Code I48.4 – Atypical atrial flutter (2026): Diagnosis, Symptoms & Billing Guide
2026 ICD-10-CM Diagnosis Code I48.4 – Atypical atrial flutter
What it is
Atypical atrial flutter is a type of supraventricular arrhythmia with a flutter pattern that does not follow the typical cavotricuspid isthmus circuit. Use this code when documentation specifically identifies atypical atrial flutter.
Clinical signs
Clinical features vary; refer to documentation. Patients may have palpitations, rapid irregular or regular atrial activity, or ECG findings consistent with flutter that is not typical atrial flutter.
When to use this code
Use I48.4 when the provider documents atypical atrial flutter as the diagnosis. It may appear in outpatient notes, discharge summaries, or rhythm interpretations when the arrhythmia is clearly identified. If the record only says “atrial flutter” without type, check documentation.
Do not use for
Do not use this code for typical atrial flutter, atrial fibrillation, or unspecified supraventricular tachycardia. If the rhythm diagnosis is unclear or mixed, check documentation before coding.
Coding tip
Code the exact arrhythmia type documented by the provider and avoid assuming “flutter” means atypical.