Atrial fibrillation is the most common sustained cardiac arrhythmia. One in 40 of the over 45s, 1 in 20 of the over 65s, 1 in 10 of the over 75s and 1 in 5 of the over 85s will have paroxysmal, persistent or permanent atrial fibrillation. Although many individuals will have idiopathic atrial fibrillation with otherwise healthy hearts and no comorbidities, its development is associated with a number of common risk factors. Every patient with a diagnosis of atrial fibrillation should have a physical examination to assess blood pressure and look for signs of valve disease and heart failure. It is routine to check thyroid function and NICE guidelines recommend echocardiographic assessment.