The results of the epicardial mapping of right and left atria in three groups of rabbits are shown in Fig. 3. Mapping images of the right atrium in three groups are shown in panels a–c, whilst graphs showing right atrial mean conduction velocity, absolute inhomogeneity and conduction inhomogeneity index are shown in panels d-f. Compared to the control group, the DM group had a lower right atrial conduction velocity (P < 0.05), higher right atrial absolute inhomogeneity (P < 0.01) and higher conduction inhomogeneity index (P < 0.05), changes that were prevented by apocynin treatment (P < 0.05). Moreover, the DM group showed lower left atrial conduction velocity (P < 0.01) but showed a trend toward recovery but did not reach statistical significance (P = 0.083). Conduction absolute inhomogeneity. Nevertheless, the DM group had a higher left atrial inhomogeneity index (P < 0.05), which was partially reversed by apocynin treatment (P < 0.05).
Fig. 3. Epicardial activation mapping of RA and LA in the 3 groups. a–c show the representative epicardial activation mapping recorded from the RA in the 3 groups. a Ctl group; b DM group; c DM-Apo group; d-f respectively show the mean conduction velocity (d) absolute inhomogeneity (e) and inhomogeneity index (f) of RA between each group. g–i Show the representative epicardial activation mapping recorded of LA in the 3 groups. g Ctl group; h DM group; i DM-Apo group; j–l respectively show the mean conduction velocity (j), absolute inhomogeneity (k) and inhomogeneity index (l) of LA among the three groups. *Compared with the Ctl group, P < 0.05; **compared with the Ctl group, P < 0.01; #compared with the DM group, P < 0.05; ##compared with the DM group, P < 0.01.
The results of the epicardial mapping of right and left atria in three groups of rabbits are shown in Fig. 3. Mapping images of the right atrium in three groups are shown in panels a–c, whilst graphs showing right atrial mean conduction velocity, absolute inhomogeneity and conduction inhomogeneity index are shown in panels d-f. Compared to the control group, the DM group had a lower right atrial conduction velocity (P < 0.05), higher right atrial absolute inhomogeneity (P < 0.01) and higher conduction inhomogeneity index (P < 0.05), changes that were prevented by apocynin treatment (P < 0.05). Moreover, the DM group showed lower left atrial conduction velocity (P < 0.01) but its recovery was only partial after apocynin treatment (P = 0.083). No significant difference in conduction absolute inhomogeneity among the three groups. Nevertheless, the DM group had a higher left atrial inhomogeneity index (P < 0.05), which was partially reversed by apocynin treatment (P < 0.05).
FIGURE 5. MKK4cko-TAC mice are more susceptible to ventricular arrhythmias and slowed conduction velocity. A, subjected to a train of eight stimuli (S1 at 100 ms) with a premature stimulus at 90 ms (S2). No episodes of arrhythmias were induced in the MKK4f/f-TAC heart (upper panel); however, ventricular tachycardia was induced in the MKK4cko-TAC heart (lower panel) (scale bar: 200 ms). B, the ventricular effective refractory period was measured using the same S1-S2 protocol, showing a prolonged ventricular effective refractory period in the MKK4cko-TAC heart (n = 6–13 per group). C, representative epicardial activation maps recorded from the MKK4f/f and MKK4cko hearts of TAC-treated mice. Earliest activation is found in red, the latest activation is shown in blue, and numbers indicate activation time (ms). The slowing of conduction and propagation of excitation was seen in the MKK4cko-TAC heart. D, summary data illustrate that both longitudinal CV and transverse CV were significantly slower in the MKK4cko heart (n= 3 per group). Data are presented as mean ± S.E.
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