MPO and atrial fibrillation: Total EAT and subepicardial MPO-stained areas were the largest in left atrial tissue in patients with persistent AF (FC 13.3, and FC 12.87, p < 0.0001) and were increased in patients with future onset AF (FC 2.4, p = 0.02, and FC 1.53, p = 0.03), compared to non-AF patients (Fig. 4, Fig. 5a, b).