Heart AtriaMyocytes, CardiacCardiac OutputHeartArrhythmias, CardiacCardiac Surgical ProceduresDeath, Sudden, CardiacCardiomegalyCardiac TamponadeCardiac Pacing, ArtificialHeart DiseasesMyocardiumCardiac CatheterizationMyocardial ContractionHeart ArrestHeart VentriclesMyoblasts, CardiacHeart FailureCardiomyopathiesCardiac MyosinsCardiac Imaging TechniquesElectrocardiographyCardiac GlycosidesHeart RateEchocardiographyCardiac Output, LowOut-of-Hospital Cardiac ArrestTime Factors