The expression levels of HCN2 and HCN4 mRNA and proteins, as well as miR-1 and miR-133, among adult and aged patients with sinus rhythm or atrial fibrillation were compared in order to determine whether age-associated changes in expression may contribute to the pathogenesis of age-associated atrial fibrillation. This evidence concerns the gene HCN2 and atrial fibrillation.