title: Heart rate variability and the outcome of head-up tilt in syncopal children.
abstract: OBJECTIVE
  This study evaluated autonomic nervous system function in 5 young (6-10 years old) and 5 older (10-15 years) children with recurrent episodes of neurally mediated syncope and a positive tilt-test result, 10 with syncope but a negative test result and 30 age-matched healthy volunteers.
  
  
  METHODS
  Time- (SDNN, SDNNi, SDANNi, rMSSD, pNN50) and frequency-domain indices (LF, HF, LF/HF) of heart rate variability (HRV) were measured during a 24-hour Holter recording and for 5 min. segments before and during 90 degrees head-up tilt (tests lasted 30 min. or until syncope occurred).
  
  
  RESULTS
  24-hour HRV-indices were within the normal range for all syncopal patients. Mean RR interval and HRV-indices, except LF/HF, were higher in the older children with a positive test result before they were tilted and during the first 5 min. of head-up tilt. HRV-indices tended to be lower after tilt in the younger children with a positive test result. SDNN and LF in older children with a positive test result and LF/HF in the younger ones increased during the 5 min preceding the syncope. No difference was observed between syncopal children with a negative test result and controls.
  
  
  CONCLUSIONS
  This study confirms that patients with vasovagal syncope have no chronic differences from normal subjects in autonomic nervous system activity. The modulation of the autonomic tone during head-up tilt is abnormal in children who faint during the test, but younger and older patients respond differently to the orthostatic stimulus.
authors.affiliation: Division of Paediatric Cardiology at CHR Citadelle, University of Liège, Belgium. Martial.Massin@chrcitadelle.be
authors.forename: M M
authors.initials: MM
authors.lastname: Massin
authors.forename: V
authors.initials: V
authors.lastname: Henrard
authors.forename: P
authors.initials: P
authors.lastname: Gerard
mesh_terms: D000293:Adolescent; D002648:Child; D002940:Circadian Rhythm / Q000502:physiology*; D015716:Electrocardiography, Ambulatory; D005260:Female; D006339:Heart Rate / Q000502:physiology*; D006801:Humans; D008297:Male; D012008:Recurrence; D012189:Retrospective Studies; D019462:Syncope, Vasovagal / Q000175:diagnosis / Q000503:physiopathology*; D018667:Tilt-Table Test; D014630:Vagus Nerve / Q000503:physiopathology*