Atrial fibrillation (AF) is the most common persistent cardiac arrhythmia, and it is predicted that one of four middle-aged adults in developed countries will develop AF. By 2030, 14-17 million patients with AF are expected in the European Union, with 120.000-215.000 newly diagnosed patients per year. AF is independently associated with an increased risk of death and high morbidity, such as heart failure and stroke, but also with frequent hospitalizations and reduced quality of life. AF usually progresses from short, rare paroxysmal episodes to longer and more frequent attacks, culminating as persistent AF. Although the pattern of AF may be the same, the mechanisms that induce AF vary significantly between patients.