Arrhythmias, CardiacArrhythmia, SinusMyocytes, CardiacElectrocardiographyHeartDeath, Sudden, CardiacCardiac OutputTachycardia, VentricularAnti-Arrhythmia AgentsVentricular FibrillationCardiac Surgical ProceduresCardiac Pacing, ArtificialHeart Conduction SystemHeart VentriclesHeart RateMyocardiumVentricular Premature ComplexesElectrocardiography, AmbulatoryTachycardiaHeart DiseasesLong QT SyndromeCardiac Complexes, PrematureMyocardial ContractionAtrial FibrillationCardiomegalyHeart ArrestElectrophysiologic Techniques, CardiacTime FactorsDogsCardiomyopathiesDefibrillators, ImplantableMyocardial InfarctionHeart FailureCardiac CatheterizationCardiac TamponadeHeart AtriaMyocardial IschemiaTachycardia, SupraventricularEchocardiographyModels, CardiovascularVentricular DysfunctionCatheter AblationAtrial FlutterNAV1.5 Voltage-Gated Sodium ChannelAction PotentialsHemodynamicsElectric CountershockCardiac ElectrophysiologyVentricular Function, LeftTreatment OutcomeBradycardiaCardiac Imaging TechniquesFlecainideMyocardial Reperfusion InjuryCardiomyopathy, DilatedFollow-Up StudiesHeart Defects, CongenitalTorsades de PointesAmiodaroneMyoblasts, CardiacBlood PressureStroke VolumeCardiac GlycosidesCardiac Output, LowPericardiumVentricular RemodelingHeart BlockVentricular FunctionCardiac MyosinsProspective StudiesDisease Models, AnimalPacemaker, ArtificialDeath, SuddenDigitalis GlycosidesCardiotonic AgentsHeart TransplantationElectrophysiologyVentricular Dysfunction, LeftRisk FactorsOut-of-Hospital Cardiac ArrestEther-A-Go-Go Potassium ChannelsCardiac VolumeHeart Function TestsSodium ChannelsCalciumAdrenergic beta-AntagonistsTroponin IAutonomic Nervous SystemRetrospective StudiesBody Surface Potential MappingSyncopePostoperative ComplicationsPredictive Value of TestsRats, Sprague-DawleyAconitineFibrosisConnexin 43TelemetryEndocardiumIsoproterenol