GRK5 and systolic heart failure: G-protein receptor kinase 5 (GRK5) Gln41 > Leu and β1-adrenergic receptor (ADRB1) Arg389 > Gly polymorphisms presented the different distribution of genotype frequencies between Caucasian American and African American, and produced the difference in β-blocker treatment effect among them with systolic heart failure (SHF).