Myocytes, CardiacMyocardiumHeartHeart VentriclesMyocardial ContractionCells, CulturedCardiomegalyCalciumMuscle CellsAnimals, NewbornCardiac OutputRats, Sprague-DawleyArrhythmias, CardiacCalcium Channels, L-TypeIsoproterenolVentricular FunctionSodium-Calcium ExchangerSarcolemmaPatch-Clamp TechniquesCardiac Surgical ProceduresCalcium SignalingRats, WistarGuinea PigsSarcomeresDeath, Sudden, CardiacSarcoplasmic ReticulumHeart AtriaAdrenergic beta-AgonistsMembrane PotentialsMitochondria, HeartAction PotentialsCardiomyopathiesCell SizeTime FactorsModels, CardiovascularReceptors, Adrenergic, betaHeart FailurePotassium ChannelsHeart DiseasesSarcoplasmic Reticulum Calcium-Transporting ATPasesCardiac Pacing, ArtificialCardiotonic AgentsMuscle ProteinsSignal TransductionRyanodine Receptor Calcium Release ChannelAtrial Natriuretic FactorRNA, MessengerCalcium ChannelsGATA4 Transcription FactorRabbitsDogsMyocardial IschemiaElectrophysiologyCaveolin 3PhenylephrineReceptors, Adrenergic, beta-1Troponin ICardiac TamponadeCardiac MyosinsMyosin Heavy ChainsMyocardial Reperfusion InjuryMyoblasts, CardiacEndothelin-1CaffeineMice, TransgenicVentricular RemodelingMyocardial InfarctionCardiomyopathy, DilatedCardiac CatheterizationMicroscopy, ConfocalSodium ChannelsPhosphorylationEnzyme InhibitorsExcitation Contraction CouplingReceptors, Adrenergic, alpha-1Mice, KnockoutCyclic AMP-Dependent Protein KinasesMyocarditisMyofibrilsCardiac Output, LowHeart RateDose-Response Relationship, DrugGene Expression RegulationElectrocardiographyProtein Kinase CHeart ArrestHypertrophyElectric ConductivitySodiumEchocardiographyDisease Models, AnimalCell SeparationHeart Conduction SystemAngiotensin IISodium-Potassium-Exchanging ATPaseVentricular Function, LeftPericardiumMuscle Fibers, SkeletalHemodynamicsAnti-Arrhythmia Agents