ADORA2A and hydrops fetalis: Small et al. demonstrated that α2CDel322–325 polymorphism is associated with high HF risk (Small et al., 2002; Davis and Johnson, 2011) probably because this variant was associated to increased α2-AR-related CAs secretion/outflow (as shown in vitro) (Small et al., 2000) and subsequent detrimental cardiotoxicity due to β-AR downregulation/desensitization.