Orthostatic sympathetic derangement in subjects with fibromyalgia (FM)

OBJECTIVE: To assess the sympathetic-parasympathetic balance

in individuals with fibromyalgia (FM), and its response to

orthostatic stress, by power spectral analysis of heart rate


METHODS: We studied 19 women with FM and 19 age

matched controls. A high resolution electrocardiogram was

obtained in supine and standing postures after achieving a

stable heart rate. Spectral analysis of R-R intervals was done

by the fast Fourier transform algorithm.

RESULTS: Analyses of

the different frequency components revealed significant

difference between the 2 groups in the low frequency

(0.050-0.150 Hz) band, which reflects modulation of the

sympathetic nervous system. Controls displayed an increased

power spectral density upon standing (+0.081 +/- 0.217 Hz);

individuals with FM had a discordant response (-0.057 +/-

0.097 Hz) (p = 0.018).

CONCLUSION: In FM, there is a deranged

sympathetic response to orthostatic stress. This abnormality

may have implications regarding the pathogenesis of FM.

MCM: Used power-spectral analysis of heart-rate variability

(see for example article UI=97138595). Found that FM pts had

a “deranged sympathetic response to orthostatic stress”

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