ADRB1 and heart failure: The present study demonstrates that black South Africans are ubiquitously homozygous for the risk α2C-AR Del322-325 variant, and that with this high-risk genetic background for the α2C-AR Del322-325 variant,18 the Gly389Arg polymorphism of the β1-AR gene neither predicts an increased risk for the expression of the clinical phenotype of heart failure in IDC, nor determines disease severity or progression of IDC after six months of standard medical therapy in the absence of β-AR blockers in this population group.