Myocardial sleeves of the pulmonary veins (PVs) act as triggering foci for the great majority of patients with paroxysmal atrial fibrillation (AF). Although the exact mechanisms are not completely understood, studies have focused on electrophysiological properties of PVs and the adjacent left atrial myocardium. As a potential explanation, PV myocytes are more prone to autonomicnervous system (ANS) stimulation and associated shortening of action potential duration, early after depolarization formation and triggered firing compared to myocytes of the adjacent left atrium (LA).