Autonomic Function in Adolescents with Orthostatic Dysregulation Measured by Heart Rate Variability

We evaluated the responses of autonomic nervous system to transient positional changes and daily changes in orthostatic dysregulation (OD) patients in order to clarify the mechanisms underlying the appearance of symptoms. The control group consisted of 16 healthy adolescents (8 males and 8 females), and the OD group consisted of 25 adolescents (13 males and 12 females). Each subject underwent continuous electrocardiographic monitoring during the head-up tilt test, followed by electrocardiographic monitoring for 24 h. Low frequency power (LF) and high frequency power (HF) were calculated as indices of autonomic function. During 0–5 min in the standing position in the tilt test, HF was higher in the OD group than in the control group (180±110 ms 2 vs . 42.6±54.1 ms 2 ; p