Echocardiography revealed that the B1KO mice display significantly decreased ejection fraction compared to control wild type (WT) mice, both under normal conditions (sham groups) and at 4 weeks post-MI, as expected since the β1AR is the major βAR subtype in the heart stimulating contractility (Table 1) [8]. This evidence concerns the gene ADRB2 and myocardial infarction.