A notable example is the GENETIC-AF trial (Genotype-Directed Comparative Effectiveness Trial of Bucindolol and Toprol-XL for the Prevention of Symptomatic Atrial Fibrillation/Atrial Flutter in Patients with Heart Failure), which compared the efficacy of bucindolol and metoprolol succinate in maintaining sinus rhythm in HFrEF patients with the ADRB1 Arg389Arg genotype [67]. This evidence concerns the gene ADRB1 and atrial fibrillation.