The American Heart Association, American College of Cardiology, and the European Society of Cardiology have proposed the following classification system based on simplicity and clinical relevance.

• First detected atrial fibrillation: Any patient newly diagnosed with AFib fits in this category, as the exact onset and chronicity of the disease is often uncertain.
• Recurrent atrial fibrillation: Any patient with 2 or more identified episodes of AF is said to have recurrent AFib. This is further classified into paroxysmal, persistent and permanent based on when the episode terminates without therapy. AF is said to be paroxysmal when it terminates spontaneously within 7 days, most commonly within 24 hours. Persistent AFib usually requires external help in the form a cardioversion or antiarrhythmic drugs to get back into normal rhythm. Whereas, permanent AFib patients fail to stay in rhythm despite cardioversion and/or antiarrhythmic drugs.
• Lone atrial fibrillation (LAF) is defined as atrial fibrillation in the absence of clinical or echocardiographic findings of cardiopulmonary disease or any other causative factors that could result in AFib.