ADRB2 and hydrops fetalis: In systolic HF, patients may actually have decreased ANS neuronal density & function, resulting in decreased NE concentration within the cardiomyocytes, in addition to decreased postsynaptic βAR density, due to depletion of cardiac ANS neuronal NE stores and decreased NE presynaptic reuptake secondary to NE transporter downregulation (Regitz et al., 1991; Backs et al., 2001).