Figure 1.

(a) Representative histological staining of atrial myocardium. A: structurally normal atrial myocardium in sham-operated group; B: in control group, severe myolysis was found; C: in spironolactone group, these myolysis changes were mostly inhibited (HE, A, C ×100; B ×400). (b) The percentage of myolysis in atrial myocardium. After 6-week rapid atrial pacing, considerable numbers of atrial myocytes were typically affected by myolysis. With the treatment of spironolactone, the number of both mildly and severely affected myocytes decreased dramatically, although still higher than that in sham-operated group. ^##P < 0.01, compared with the sham-operated group; **P < 0.01, compared with the control group. HE, haematoxylin-eosin.