Usefulness of Endothelin-1 as a Predictor of Response to Head-Up Tilt-Table Testing in Children With Syncope

Recurrent syncope in children and adolescents is a frequently encountered problem in the practice of pediatrics. The etiology of syncope in otherwise healthy persons is considered as a neurally mediated vasovagal reaction. It is postulated that neurally mediated syncope occurs during rapid or prolonged upright positioning. This results in decreased preload, increased ventricular contraction, and sudden activation of cardiac mechanoreceptors by way of the afferent unmyelinated C-fibers.l This causes central sympathetic withdrawal and vagal enhancement, thereby promoting vasodilatation, bradycardia and decreased cerebral perfusion, and syncope.