title: Heart rate variability analysis during head-up tilt test predicts nitroglycerine-induced syncope.
abstract: The aim of this study was to determine whether or not heart rate variability (HRV) analysis during the first 20 min of head-up tilt testing could predict whether patients will develop syncope after nitroglycerine administration.
  
  
  
  64 patients with previous loss of consciousness underwent head-up tilt testing with the Italian protocol, which involves the administration of nitroglycerine after 20 min of tilt. HRV parameters were analysed from 5 min intervals selected during pretest supine rest (phase 1), the first 5 min (phase 2) and the last 5 min (phase 3) of passive 20 min of tilting, prior to the administration of nitroglycerine. Differences in power (ms(2)) of the spectral components between the various phases of tilting were calculated for each patient and expressed as Δ.
  
  
  
  20 patients (group 1, 9 women, mean age 43.2±24.5 years) had a syncope during tilt testing after nitroglycerine, while the other 44 (group 2, 24 women, mean age 41±20.5 years) did not. In group 1, the HRV spectral parameters high frequency (HF) and total power (TP) had a significant decrement from phases 2 to 3 (p=0.012 and 0.027, respectively), while in group 2 the average HF and TP values did not change. The Δ of spectral parameters between phases 2 and 3 were able to differentiate between the two groups and to predict syncope after nitroglycerine administration (p<0.05).
  
  
  
  HRV analysis within the first 20 min of passive tilting demonstrated that patients with nitroglycerine-induced syncope are characterised by a progressive decrement of parasympathetic activity, which does not occur in patients with a negative response to nitroglycerine. If confirmed on a wider population, HRV analysis could replace nitroglycerine administration and shorten the duration of the tilt test.
authors.affiliation: Catholic University of the Sacred Heart, Biomagnetism Center, Clinical Physiology , Rome , Italy.
authors.forename: Kristian
authors.initials: K
authors.lastname: Efremov
authors.affiliation: Catholic University of the Sacred Heart, Biomagnetism Center, Clinical Physiology , Rome , Italy.
authors.forename: Donatella
authors.initials: D
authors.lastname: Brisinda
authors.affiliation: Catholic University of the Sacred Heart, Biomagnetism Center, Clinical Physiology , Rome , Italy.
authors.forename: Angela
authors.initials: A
authors.lastname: Venuti
authors.affiliation: Catholic University of the Sacred Heart, Biomagnetism Center, Clinical Physiology , Rome , Italy.
authors.forename: Emilia
authors.initials: E
authors.lastname: Iantorno
authors.affiliation: Catholic University of the Sacred Heart, Biomagnetism Center, Clinical Physiology , Rome , Italy.
authors.forename: Claudia
authors.initials: C
authors.lastname: Cataldi
authors.affiliation: Catholic University of the Sacred Heart, Biomagnetism Center, Clinical Physiology , Rome , Italy.
authors.forename: Francesco
authors.initials: F
authors.lastname: Fioravanti
authors.affiliation: Catholic University of the Sacred Heart, Biomagnetism Center, Clinical Physiology , Rome , Italy.
authors.forename: Riccardo
authors.initials: R
authors.lastname: Fenici
keywords: Syncope