Expanding knowledge of the pathogenesis of myocardial fibrosis induced by galectin-3 and an increase in the concentration of type I and III procollagens is important, since a high level of galectin-3, in our opinion, is a predictor of arrhythmia progression and can be considered as an additional indication for catheter radiofrequency ablation in patients with AF. The gene discussed is LGALS3; the disease is atrial fibrillation.