ADRB1 and cardiac arrhythmia: In this study, we, for the first time, displayed the involvement of let-7, a conserved and abundant miRNA in the heart [30], in the up-regulation of β1-AR in AMI in rats, which provides new insight into the mechanisms for regulation of β1-AR expression and overexpression of miRNA let-7e potentially inhibited AMI-induced arrhythmia in rat.