房颤时，电脉冲在心房内和心房周围的许多其他部位（异位），通常接近肺静脉根部，随机产生。 A: In atrial fibrillation, electrical stimuli are relayed randomly from many other sites called ectopic sites in and around the auricle, commonly near the roofs of pulmonary veins. B: In atrial fibrillation, electrical impulses are initiated randomly from many other sites called ectopic sites in and around the atria, commonly near the roots of pulmonary veins.