AmiodaroneAnti-Arrhythmia AgentsBenzofuransWithholding TreatmentAtrial FibrillationTreatment OutcomeTachycardiaSotalolTachycardia, VentricularTime FactorsDrug Therapy, CombinationThyrotoxicosisRecurrenceDouble-Blind MethodDrug Administration ScheduleVentricular FibrillationArrhythmias, CardiacElectric CountershockFollow-Up StudiesElectrocardiographyPropafenoneDose-Response Relationship, DrugSubstance Withdrawal SyndromeAdministration, OralRetrospective StudiesProspective StudiesTachycardia, Paroxysmal