SCN3B and atrial fibrillation: This study aimed to: (1) evaluate the expression of peripheral blood serum IL-2 in patients with AF, (2) verify the correlation between IL-2 and miR-190-5p expression in myocardial tissues of patients with AF, (3) clarify the role of miR-190a-5p in regulating the abnormal electrical activity of sodium current density in SCN3B, and (4) reveal the possibility of miR-190a-5p being a protective factor against the progress of CAs through negative regulation of IL-2.