BackgroundMyocardial damage in myocarditis is mediated, in part, by immunological mechanisms. High-dose intravenous γ-globulin (IVIG) is an immunomodulatory agent that is beneficial in myocarditis secondary to Kawasaki disease, as well as in murine myocarditis. Since 1990, the routine management of presumed acute myocarditis at Children's Hospital, Boston, and Children's Hospital, Los Angeles, has included administration of high-dose IVIG.Methods and ResultsWe treated 21 consecutive children presenting with presumed acute myocarditis with IVIG, 2 g/kg, over 24 hours, in addition to anticongestive therapies. A comparison group comprised 25 recent historical control patients meeting identical eligibility criteria but not receiving IVIG therapy. Left ventricular function was assessed during five time intervals: 0 to 7 days, 1 to 3 weeks, 3 weeks to 3 months, 3 to 6 months, and 6 to 12 months. At presentation, the IVIG and non-IVIG groups had comparable left ventricular enlargement and poor fractional shortening. Compared with the non-IVIG group, those treated with IVIG had a smaller mean adjusted left ventricular end-diastolic dimension and higher fractional shortening in the periods from 3 to 6 months (P= .008 andP= .033, respectively) and 6 to 12 months (P= .072 andP= .029, respectively). When adjusting for age, biopsy status, intravenous inotropic agents, and angiotensinconverting enzyme inhibitors, patients treated with IVIG were more likely to achieve normal left ventricular function during the first year after presentation (P= .03). By 1 year after presentation, the probability of survival tended to be higher among IVIG-treated patients (.84 versus .60,P= .069). We observed no adverse effects of IVIG administration.ConclusionsThese data suggest that use of high-dose IVIG for treatment of acute myocarditis is associated with improved recovery of left ventricular function and with a tendency to better survival during the first year after presentation.