Atrial Function, LeftAtrial FunctionHeart AtriaAtrial Function, RightEchocardiography, DopplerMyocardial ContractionMuscle ContractionEchocardiography, Doppler, PulsedAtrial FibrillationAtrial Premature ComplexesVentricular Function, LeftBlood Flow VelocityEchocardiographyPericardiectomyElectric CountershockMitral ValveFetal HeartDiastoleIsometric ContractionStroke VolumePerinephritisHeart Function TestsObserver VariationHemodynamicsPulmonary VeinsVentricular FunctionEchocardiography, TransesophagealUterine ContractionVentricular Dysfunction, LeftElectrocardiographyTricuspid ValveUltrasonography, PrenatalSystoleHeart VentriclesUltrasonography, DopplerMitral Valve StenosisHeart RateDogsCardiac Pacing, ArtificialHeart Conduction SystemBradycardiaVena Cava, InferiorMitral Valve InsufficiencyMuscle, SmoothHeartHeart Defects, CongenitalPulmonary Wedge PressureHeart Valve DiseasesGestational AgeTime FactorsObservationCardiomegalyPregnancyElectric StimulationMuscle, SkeletalCardiac CatheterizationVasoconstrictionHypertrophy, Left VentricularIsotonic ContractionCalciumProspective StudiesBlood PressureGuinea PigsChronic Disease