This sympatholysis, coupled with its potent inverse agonism at cardiac βARs (especially at the β1AR), and with its significant affinity for all three types of cardiac ARs (β1AR, β2AR, α1AR), culminates in a powerful, almost complete adrenergic blockade by carvedilol in human HF [17,35]. The gene discussed is ADRB2; the disease is hydrops fetalis.