Methods: Forty eight male Lewis rats of 6-8 weeks were randomly divided into normal control group,EAM group,CD40siRNA group and siRNA group,with 12 rats in each group.On day 21,6 rats were sacrificed respectively in each group,on day 56,the remaining rats were sacrificed,we observed histopathologic and ultrastructure changes by light and electron microscope,myocardial histopathologic scores were counted,then cTnT,BNP and IL-22 were tested by ELISA.Result: On days 21 and 56,the total incidence of each group was 100%except the normal control and there was no statistical difference about the survival rate and mortality in each group(P> 0.05); myocardial histopathology scores,the serum level of cTnT and BNP in CD40siRNA group was significantly lower than that in EAM group(P<0.05),the serum level of IL-22 was higher than EAM group(P<0.05),and the serum level of cTnT and BNP had positive correlation with myocardial histopathology scores(r=0.732,r=0.869,P<0.05).Conclusion: Silencing CD40 by siRNA can relieve the inflammation in EAM,reduce the degree of myocardial injury and improve the function of heart.The mechanism may be related with the up-regulation of IL-22 expression and the inhibition of immune response.