Heart RateHeartHeart Rate, FetalHeart FailureAutonomic Nervous SystemBlood PressureHeart DiseasesHeart TransplantationHeart Defects, CongenitalHemodynamicsFetal HeartSympathetic Nervous SystemElectrocardiography, AmbulatoryBaroreflexHeart AtriaElectrocardiographyAdrenergic beta-AntagonistsHeart Valves