Action PotentialsArrhythmias, CardiacMyocytes, CardiacHeartArrhythmia, SinusElectrocardiographyAnti-Arrhythmia AgentsHeart Conduction SystemElectrophysiologyHeart VentriclesDeath, Sudden, CardiacPatch-Clamp TechniquesTachycardia, VentricularMembrane PotentialsVentricular FibrillationElectric StimulationMyocardiumCardiac OutputSodium ChannelsVentricular FunctionCardiac Pacing, ArtificialCalciumTetrodotoxinTime FactorsGuinea PigsMyocardial ContractionPotassium ChannelsDogsModels, CardiovascularLong QT SyndromeHeart RateCardiac Surgical ProceduresHeart AtriaPotassiumVentricular Premature ComplexesPapillary MusclesPurkinje FibersNeuronsCardiac Complexes, PrematureNeural ConductionTachycardiaElectrophysiologic Techniques, CardiacPotassium Channels, Voltage-GatedAtrial FibrillationElectric ConductivityPericardiumRefractory Period, ElectrophysiologicalElectrocardiography, AmbulatorySodiumPotassium Channel BlockersRats, Sprague-DawleyHeart DiseasesNAV1.5 Voltage-Gated Sodium ChannelCardiomegalyVoltage-Sensitive Dye ImagingEndocardiumMicroelectrodes4-AminopyridineEther-A-Go-Go Potassium ChannelsAxonsCalcium Channels, L-TypeSodium Channel BlockersRats, WistarSinoatrial NodeHeart FailureSynaptic TransmissionIon ChannelsCardiomyopathiesMyocardial InfarctionCardiac ElectrophysiologyTorsades de PointesHeart ArrestPyramidal CellsAtrial FunctionMyocardial IschemiaDendritesCalcium SignalingRabbitsDefibrillators, ImplantableQuinidineCardiac CatheterizationDelayed Rectifier Potassium ChannelsTachycardia, SupraventricularIon Channel GatingSynapsesTetraethylammonium CompoundsCalcium ChannelsFlecainideVentricular DysfunctionAtrial FlutterCardiac TamponadeElectrophysiological PhenomenaCells, CulturedElectric CountershockEchocardiographyIsoproterenolLidocaineCatheter AblationAnimals, NewbornCalcium Channel Blockers