SMAD2 and atrial fibrillation: Han et al. [18] reported that up-regulating miR-29b could block the TGF-β1/Smad-2/3 signaling pathway to mitigate atrial fibrosis in AF rats Therefore, to better explore the mechanism of miR-499-5p on inhibiting atrial fibrosis in our work, the TGF-βl/Smad2 pathway was measured in the present study.