Clinical significance of corticosteroid therapy for eosinophilic myocarditis

The recommended treatment for eosinophilic myocarditis (EM), pathologically defined as myocardial inflammation with eosinophil infiltration, is corticosteroids. Although EM has a wide variety of clinical features including the degree of eosinophilic infiltration, there have been no reports on how patients with EM should be treated with corticosteroids irrespective of their pathological findings.Thirty-seven consecutive patients with acute myocarditis hospitalized in our institute between 1996-2009 were enrolled. Excluding those with secondary EM such as Loeffler's endocarditis, hypereosinophilic syndrome, and Churg-Strauss Syndrome, together with drug-induced allergic myocarditis, the subjects were divided into 2 groups according to the existence of eosinophils in the myocardial interstitium observed in endomyocardial biopsy specimens. There were no differences in the clinical characteristics on admission between the 2 groups: with (group EM, n = 22) and without (group lymphocytic myocarditis (LM), n = 7) eosinophilic infiltrates irrespective of pathological differences. The treatment policy has been consistent in our institution: intensive hemodynamic observation and support without corticosteroid administration, not only in LM but also in idiopathic EM. There was no significant difference in clinical recovery in the acute phase as indicated by the hospitalization period, left ventricular ejection fraction, or long-term prognosis in EM compared to LM.A conventional management strategy for idiopathic EM without corticosteroid administration can improve the prognosis in the acute and chronic phases, similar to that of LM.