Objective To observe the protective effect of different doses of left carnitine on cardiomyocyte function in children with viral myocarditis.Methods94 cases of children with viral myocarditis were selected and divided into observation group and control group according to the random number table, 47 cases in each group.Both groups were treated with fructose 1,6-diphosphate(100~250mg/kg, add 150mL of 10% glucose in intravenous infusion, 1times/d) combined with left carnitine.Large dose group of left carnitine 100 mg/kg, low dose group 50mg/kg, all added 150mL of 5% glucose intravenous infusion, 1 times/d.The total effective rate, creatine kinase(CK), creatine kinase isoenzyme (CK-MB),lactate dehydrogenase (LDH), cardiac ejection fraction(EF), ventricular short axis shortening (FS) And the total incidence of adverse reactions were compared between two groups.ResultsThe total effective rates of two group were 93.62% and 87.23%.The level of CK,CK-MB,LDH in two groups were significantly decreased after treatment of two weeks(P<0.05), EF, FS were increased after treatment of two weeks(P<0.05).There was no significant difference in CK, CK-MB, LDH, EF and FS between the high dose group and the low dose group after treatment of two weeks.The overall incidence of adverse reactions in the high dose group was 25.53%, which was lower than that in the low dose group (8.51%,P<0.05).ConclusionThe use of low-dose left carnitine in children with viral myocarditis can effectively remove free radicals, protect cardiomyocyte function and improve myocardial energy metabolism and cardiac function, and safer than high-dose groups.