MMP13 and atrial fibrillation: The IHC results showed that compared with the Ctrl group (MMP‐13: 9.17% ± 3.76%; ADAMTS‐4: 22.83% ± 7.76%), the positive cell ratios in the AF of the mice in the 12‐week group (MMP‐13: 30.33% ± 6.35%, P = 0.003; ADAMTS‐4: 57.5% ± 7.91%, P = 0.005) and the 16‐week group (MMP‐13: 67.17% ± 6.85%, P<0.001; ADAMTS‐4: 75.8% ± 10.35%, P < 0.001) was significantly increased (Fig. 2B, C).