I48.91 Unspecified atrial fibrillation

Billable ICD-10-CM code, FY2026.

Risk adjustment (HCC)

• CMS-HCC V28: HCC 238 — Specified Heart Arrhythmias
• CMS-HCC V22: HCC 96 — Specified Heart Arrhythmias
• RxHCC V08: HCC 193 — Atrial Arrhythmias
• ESRD V24: HCC 96

MS-DRG index

Defines the logic of DRG(s) 308-310 in MDC 05.

Approximate ICD-9-CM (GEMs)

• 427.31 Atrial fibrillation (approximate)

Code annotations containing back-references to I48.91

Back-references to I48

• Code Also: M35.81 Multisystem inflammatory syndrome ("cardiac arrhythmia (I47-I49.-)")
• Type 2 Excludes: R00 Abnormalities of heart beat ("specified arrhythmias (I47-I49)")

Diagnosis Index entries for I48.91

• Fibrillation › atrial or auricular (established)

Nearby codes

• I48.20 Chronic atrial fibrillation, unspecified
• I48.21 Permanent atrial fibrillation
• I48.3 Typical atrial flutter
• I48.4 Atypical atrial flutter
• I48.9 Unspecified atrial fibrillation and atrial flutter
• I48.91 Unspecified atrial fibrillation (this code)
• I48.92 Unspecified atrial flutter