Atrial fibrillation (AF) is the most common clinical arrhythmia. AF is associated with increased risk for stroke due to blood clots formed in the fibrillating atria. Some patient characteristics increase the likelyhood of AF and at the same time the risk of stroke when AF has developed. To reduce the risk of stroke, anticoagulation therapy is recommended in patients with AF and risk factors (such as high blood pressure, diabetes, vessel disease). However, occasional (paroxysmal) AF may occur without symptoms and remain undetected, leaving patients at risk.