Response of plasma renin activity to postural change in vasovagal syncope in children, with observations on syncope

37 children aged 7-14 years with a history of repetitive fainting (vasovagal syncope) were studied. Plasma renin activity (PRA), blood pressure and heart rate were measured before and after standing for 15 min. Standing PRA was significantly higher in cases of fainting (n = 14) than in cases of nonfainting (n = 23). A significant positive correlation was observed between PRA and fall in systolic blood pressure on standing in cases of fainting, but not in cases of nonfainting. These findings suggest that the renin-angiotensin system may respond to the fall in blood pressure in children subject to fainting, unlike their adult counterparts previously reported.