Convert to ICD-10-CM: 
427.31 converts approximately to:
- 2015/16 ICD-10-CM I48.91 Unspecified atrial fibrillation
 ICD-9-CM Volume 2 Index entries containing back-references to 
427.31:
- Fibrillation atrial (established) (paroxysmal) 427.31 atrial (established) (paroxysmal) 427.31
  auricular (atrial) (established) 427.31 auricular (atrial) (established) 427.31