Electric CountershockTechnetium Tc 99m PyrophosphateVentricular FibrillationElectric OrganMyocytes, CardiacCardiac OutputElectromagnetic FieldsGymnotiformesHeartElectric StimulationElectric InjuriesArrhythmias, CardiacCardiac Surgical ProceduresDeath, Sudden, CardiacElectric WiringElectric ConductivityCardiac Pacing, ArtificialCardiomegalyCardiac TamponadeMyocardiumHeart DiseasesCardiac CatheterizationElectric Power SuppliesElectroporationMyocardial ContractionTorpedoHeart VentriclesTime FactorsHeart ArrestElectric ImpedanceElectrocardiography