ADRB1 and idiopathic dilated cardiomyopathy: The aims of the present study were therefore to assess the relationship between the β1-AR Gly389Arg and α2C-AR Del322-325 variants and (1) the presence, (2) the severity and (3) the progression of idiopathic dilated cardiomyopathy (IDC) in a relatively large sample of black South Africans studied at a time when β-AR-blocker therapy was not indicated as standard care in South Africa.