Neurally mediated hypotension & autonomic dysfunction measured by heart rate variability during head-up tilt testing in children with Chronic Fatigue Syndrome (CFS)
By Stewart J, Weldon A, Arlievsky N, Li K, Munoz J •
August 10, 1998
Recent investigations suggest a role for neurally mediated
hypotension (NMH) in the symptomatology of chronic fatigue
syndrome (CFS) in adults. Our previous observations in
children with NMH and syncope (S) unrelated to CFS indicate
that the modulation of sympathetic and parasympathetic tone
measured by indices of heart rate variability (HRV) is
abnormal in children who faint during head-up tilt (HUT).
order to determine the effects of autonomic tone on HUT in
children with CFS we performed measurements of HRV during HUT
in 16 patients aged 11-19 with CFS. Data were compared to 26
patients evaluated for syncope and with 13 normal control
subjects. After 30 minutes supine, patients were tilted to 80
degrees for 40 minutes or until syncope occurred. Time domain
indices included RR interval, SDNN, RMSSD, and pNN50. An
autoregressive model was used to calculate power spectra. LFP
(.04-.15 Hz), HFP (.15-.40Hz), and TP (.01-.40Hz). Data were
obtained supine (baseline) and after HUT.
patients fainted (CFS+, 5/13 pure vasodepressor syncope) and
three patients did not (CFS-). Sixteen syncope patients
fainted (S+, all mixed vasodepressor- cardioinhibitory) and 10
did not (S-). Four control patients fainted (Control+, all
mixed vasodepressor-cardioinhibitory) and nine did not
(Control-). Baseline indices of HRV were not different between
Control+ and S+, and between Control- and S-, but were
depressed in S+ compared to S-. HRV indices were strikingly
decreased in CFS patients compared to all other groups. With
tilt, SDNN, RMSSD, and pNN50 and spectral indices decreased in
all groups, remaining much depressed in CFS compared to S or
control subjects. With HUT, sympathovagal indices (LFP/HFP,
nLFP, and nHFP) were relatively unchanged in CFS, which
contrasts with the increase in nLFP with HUT in all other
groups. With syncope RMSSD, SDNN, LFP, TP, and HFP increased
in S+ (and Control+), suggesting enhanced vagal heart rate
regulation. These increases were not observed in CFS+
CFS is associated with NMH during HUT in children.
All indices of HRV are markedly depressed in CFS patients,
even when compared with already low HRV in S+ or Control+
patients. Sympathovagal balance does not shift toward enhanced
sympathetic modulation of heart rate with HUT and there is
blunting in the overall HRV response with syncope during HUT.
Taken together these data may indicate autonomic impairment in
patients with CFS.
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