Atrial fibrillation (AF) can be treated or prevented by administering to a subject who suffers from or is at risk of suffering from AF a composition comprised of an amount of an active agent, which is 4-methoxy-N-(3,5-bis(1-pyrrolidayl)-4-hydroxy benzyl) benzene sulfonamide (sulcardine) or a pharmaceutically acceptable salt thereof, such that the Cmax value the active agent in the subject is in the range from about 1 μM to about 20 μM.
