Before accepting the diagnosis of dilated cardiomyopathy two important reversible conditions need to be ruled out:
1) Coarctation of aorta.
2) Anomalous origin of left coronary artery from pulmonary artery.
A good ECHO is necessary to specifically address this issue. We are routinely giving IgG in patients diagnosed post myocarditis cardiomyopathy because there is data to suggest that it may reverse the process. I think you should consult a pediatric cardiologist.