The quality of evidence is downgraded by study limitations (unclear allocation concealment and blinding), by indirectness (differences between the population of interest and those studied: there is doubt, whether all enrolled participants truly had acute myocarditis), and by imprecise results (few patients and outcome events).
A Cochrane review [Abstract] 1 included 3 studies with a total of 189 subjects with a clinical diagnosis of acute myocarditis.
Adults: The first study included 62 subjects with recent-onset dilated cardiomyopathy randomly assigned to receive IVIG or an equivalent volume of 0.1% albumin. There was no statistically significant difference in event-free survival (risk of death, cardiac transplant, or left ventricular assist device) between groups (RR 1.76, 95% CI 0.48 to 6.40). The second study included 41 subjects with acute myocarditis randomised to either high-dose IVIG (1 to 2 g/kg over 2 days) or no treatment. The IVIG group reported greater survival time after 60 days (P < 0.01). In the pooled analysis, no difference in overall survical was observed (RR 0.91, 95% CI 0.23 to 3.62, 2 studies, n=103).The effect of IVIG on LVEF (pooled MD −0.01, 95% CI −0.06 to 0.05; 2 studies, n=103), on functional capacity, assessed by peak oxygen consumption at 12 months (MD −0.80, 95% CI −4.57 to 2.97; 1 study, n=48), and on failure to attain complete recovery (RR 0.46, 95% CI 0.19 to 1.14; 1 study, n=41) were uncertain.
Children: 86 children presenting with acute myocarditis were randomly assigned to 1 g/kg IVIG daily for 2 consecutive days or placebo followed by echocardiography 1 and 6 months post randomisation. No difference in mortality was observed after 6 months (RR 0.48, 95% CI 0.20 to 1.15) between IVIG and control. The effect was also uncertain for improvement in LVEDD and LVSF after 6 months (LVEDD MD −4.00, 95% CI −9.52 to 1.52; LVSF no raw data).
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