The quality of evidence is downgraded by study limitations (unclear allocation concealment and lack of blinding), by inconsistency (variability in results), and by imprecise results (few patients).
A Cochrane review included 7 studies with a total of 420 subjects. The primary outcomes could not be pooled in meta-analyses due to heterogeneity. Four small studies with 20 to 30 children each, and 2 larger studies of 80 children each, showed an improvement of congestive heart failure with beta-blocker therapy. A larger study (n=161) showed no evidence of benefit over placebo in a composite measure of heart failure outcomes. The included studies showed no significant difference in mortality or heart transplantation rates between the beta-blocker and control groups. A meta-analysis of left ventricular ejection fraction (LVEF) (MD 5.99, 95% CI 1.88 to 10.11; statistical heterogeneity I2=69%; 3 studies, n=207) and left ventricular fractional shortening (LVFS) (MD 3.79, 95% CI 0.92 to 6.66; 3 studies, n=207) data showed a very small improvement with beta-blockers. No significant adverse events were reported with beta-blockers, apart from one episode of complete heart block.