Objectives To evaluate the efficiency and security of ibutilide, which is combinedly used to patients through intravenous injection, who have amiodarone per os without converting AFL/AF (＜ 365 days).Methods Selected 88 patients who were eligible for the group conditions.The control group (A) using ibutilide alone, The experimental group (B), take Ibutilide and amiodarone P.O.in combination.