Autonomic Nervous Function in Vasovagal Syncope of Children and Adolescents

Syncope is defined as a transient loss of consciousness due to global cerebral hypoperfusion, accompanied by loss of muscle tone and failure to maintain an active position. Vasovagal syncope (VVS) is the most common presentation of syncope, and its diagnostic criteria include:(1) absence of any other evident etiology for syncope or presyncope,(2) positive response to head-up tilt test with evident vasovagal reaction (hypotension and/or bradycardia), and (3) no concomitant chronic or acute disease [1, 2]. The onset of VVS peaks initially in childhood and adolescence, and accounts for 60%–70% of all syncopal cases. Clinicians pay great attention to syncope among children and adolescents, due to its high prevalence and its impact on patients’ quality of life. Affected individuals often experience mental stress, economic burdens, and accidental bodily injuries related to syncope [2]. While the pathogenesis of VVS is not fully understood, autonomic nervous dysfunction has been identified as a contributing mechanism. The examination of autonomic nervous function can provide important information about patients with syncope.