Arrhythmias, CardiacArrhythmia, SinusElectrocardiographyTachycardia, VentricularAnti-Arrhythmia AgentsVentricular FibrillationVentricular Premature ComplexesHeart Conduction SystemTachycardiaElectrocardiography, AmbulatoryCardiac Complexes, PrematureDeath, Sudden, CardiacLong QT SyndromeAtrial FibrillationTachycardia, SupraventricularHeart RateElectrophysiologic Techniques, CardiacAtrial FlutterDefibrillators, ImplantableCatheter AblationHeart VentriclesHeartCardiac Pacing, ArtificialFlecainideVentricular DysfunctionTorsades de PointesNAV1.5 Voltage-Gated Sodium ChannelDogs