Finally, we determined the amount of MPO-positive leukocytes in right atrial appendage tissue of patients with persistent AF (n = 5) or without AF (n = 4), which revealed a significantly increased number of leukocytes with enhanced MPO-deposition in sections of patients with AF as compared to control subjects (p<0.05) (Fig. 4A, B). This evidence concerns the gene MPO and atrial fibrillation.