Power spectrum analysis contribution to the detection of cardiovascular dysautonomia in multiple sclerosis.

In multiple sclerosis (MS) autonomic cardiovascular dysfunction is an uncommon, but potentially dangerous event, to which studies of spectral analysis of heart rate variability have not been applied, yet. MATERIAL AND METHODS--We studied 16 patients with definite MS (11 women and 5 men, mean age 30.3 +/- 7.4 yrs., mean EDSS 2.06 +/- 1.42) and 16 sex- and age-matched healthy controls. Besides cardiovascular reflex tests (valsalva manoeuvre, deep breathing, lying to standing, Blood Pressure response to standing and sustained handgrip), each underwent spectral analysis of the R-R interval short-term variability at rest and after tilting, to detect three components: very low frequency (VLF), low frequency (LF) and high frequency (HF). A recent brain MRI was obtained from patients, to compare plaque characteristics with spectral parameters. RESULTS--At cardiovascular reflexes, only four patients (25%) showed an impairment, mostly of a mild degree. VLF and LF at rest were lower in MS subjects than in controls (p < 0.01). No significant correlation was found between spectral parameters and lesion area or localization as detected on MRI. CONCLUSIONS--Spectral analysis could usefully flank reflex tests to detect autonomic subclinical cardiovascular abnormalities.