Song J, et al. - Researchers ascertained whether left ventricular ejection fraction (LVEF) and left ventricular fractional shortening (LVFS) could predict the effectiveness of metoprolol therapy on vasovagal syncope (VVS) in children. For this investigation, 49 children, including 30 with VVS and 19 gender- and age-matched healthy controls were recruited. They prescribed metoprolol to the VVS subjects. Results of this study suggested that baseline LVEF and LVFS could be useful predictors of the efficacy of β-blocker therapy on VVS in children.