ICD-10 Code I48.21 – Permanent atrial fibrillation (2026): Diagnosis, Symptoms & Billing Guide
2026 ICD-10-CM Diagnosis Code I48.21 – Permanent atrial fibrillation
What it is
Permanent atrial fibrillation is a chronic irregular heart rhythm that is accepted by the patient and clinician, with no further attempt to restore normal sinus rhythm. Use this code when the condition is documented as permanent.
Clinical signs
Common findings include an irregularly irregular pulse, palpitations, fatigue, shortness of breath, or reduced exercise tolerance. Clinical features vary; refer to documentation, and confirm the rhythm diagnosis is atrial fibrillation rather than another arrhythmia.
When to use this code
Use I48.21 when the provider documents permanent atrial fibrillation, including follow-up visits for ongoing management of the established condition. It also applies when the record states the rhythm is chronic and no cardioversion or rhythm-control attempt is planned. Check documentation if the note only says “atrial fibrillation” without specifying permanence.
Do not use for
Do not use this code for paroxysmal, persistent, or unspecified atrial fibrillation. If the documentation does not clearly identify the arrhythmia as permanent, you should not assume this code.
Coding tip
Look for the exact word “permanent” in the assessment or problem list before assigning I48.21.