HypovolemiaTachycardiaTachycardia, VentricularTachycardia, SupraventricularTachycardia, Atrioventricular Nodal ReentryTachycardia, ParoxysmalTachycardia, Ectopic AtrialTachycardia, SinusBlood VolumeLower Body Negative PressureCatheter AblationElectrocardiographyTachycardia, Ectopic JunctionalShockPostural Orthostatic Tachycardia SyndromeTachycardia, ReciprocatingTachycardia, Sinoatrial Nodal ReentryHeart RateHeart Conduction SystemPlasma VolumeElectrophysiologic Techniques, CardiacCardiac Pacing, ArtificialHypotension, OrthostaticAnti-Arrhythmia AgentsAtrioventricular NodeHemodynamicsDehydrationBlood Volume DeterminationFluid TherapyBundle of HisFluid ShiftsDiureticsVascular CapacitanceBody Surface Potential MappingIsotonic SolutionsPlasma SubstitutesBlood PressureFurosemideArrhythmias, CardiacShock, HemorrhagicThirstWolff-Parkinson-White SyndromeVentricular FibrillationHypernatremiaBed RestHead-Down TiltHemodilutionInappropriate ADH SyndromeHemorrhageIntracranial HypotensionStroke VolumeHypotensionDefibrillators, ImplantableCardiac OutputSupine PositionAmiodaroneElectrocardiography, AmbulatoryDogsFlecainideVentricular Premature ComplexesCryosurgeryCardiovascular SystemPostureBaroreflexHeart AtriaProcainamideEndocardiumAtrial FlutterHeart BlockBundle-Branch BlockPre-Excitation SyndromesSympathetic Nervous SystemResuscitationHyponatremiaAccessory Atrioventricular BundleDrinkingHeart VentriclesCardiac Complexes, PrematureWater-Electrolyte BalanceHydroxyethyl Starch DerivativesElectrophysiologyHematocritTime FactorsSpectroscopy, Near-InfraredDeath, Sudden, CardiacElectric CountershockSyncopeVasopressinsEpicardial Mapping