Tachycardia, SupraventricularArrhythmias, CardiacAtrial Premature ComplexesTachycardia, SinusTachycardia, Ectopic JunctionalAtrial FlutterAnti-Arrhythmia AgentsElectrocardiographyAtrial FibrillationAmiodaroneAtrioventricular NodeTachycardia, ParoxysmalWolff-Parkinson-White SyndromeCatheter AblationTachycardia, Atrioventricular Nodal ReentryTachycardiaElectrocardiography, AmbulatoryHeart Conduction SystemCardiac Pacing, ArtificialArrhythmia, SinusHeart RateFlecainideTreatment OutcomeHydrops FetalisTachycardia, VentricularFollow-Up StudiesCardiac Complexes, PrematureTime FactorsDigoxinElectrophysiologic Techniques, CardiacBundle of HisVentricular Premature ComplexesTachycardia, Ectopic AtrialVentricular FibrillationFetal DiseasesPre-Excitation SyndromesAccessory Atrioventricular BundleDefibrillators, ImplantableElectric CountershockHeart AtriaSotalolElectrocoagulationAtrioventricular BlockPropafenoneHeart BlockDeath, Sudden, CardiacHeart VentriclesAntazolineHeart Rate, FetalBradycardiaHeartDisopyramideSyncopeVerapamilSinoatrial NodeProcainamideBody Surface Potential MappingEchocardiographyPacemaker, ArtificialElectrophysiologyHeart Defects, CongenitalDogsTricuspid AtresiaRetrospective StudiesHeterotaxy SyndromeHydroxyzineRecurrenceFinancial AuditCardiac Surgical ProceduresLong QT SyndromeCardiomyopathy, DilatedAtrial FunctionIsolated Noncompaction of the Ventricular MyocardiumTachycardia, Sinoatrial Nodal ReentryPostoperative ComplicationsInfant, NewbornProspective Studies