Permanent atrial fibrillation SNOMEDCT_US:440028005 SNOMEDCT_US:426749004 HP:0004754 The natural history of atrial fibrillation (AF) is characterized by a gradual worsening with time. AF itself produces changes in atrial function and structure. Note there is no precise definition of the duration of AF required to be regarded as chronic. UMLS:C2586056 Atrial fibrillation (AF) that cannot be successfully terminated by cardioversion, and longstanding (more than 1 year) AF, where cardioversion is not indicated or has not been attempted, is termed permanent. Chronic atrial fibrillation UMLS:C0694539 Atrial fibrillation