title: Effects of spinal cord stimulation on heart rate variability in patients with chronic pain.
abstract: BACKGROUND
  Spinal cord stimulation has become an established clinical option for treatment of refractory chronic pain and angina pectoris, but its precise mechanism of action is unclear. We investigated the effect of spinal cord stimulation (SCS) on heart rate variability (HRV) and evaluating its influence on the sympathetic/parasympathetic balance in chronic pain. MATERIALS AND PURPOSE: Seven patients (three men, four women) with SCS due to chronic pain were included. The SCS was programmed in three different ways: (i) to stimulate at an amplitude known to generate paresthesias (ON-state), (ii) at a subliminal level (SUB state), or (iii) switched off (OFF-state). HRV analysis was based on 5-min segments of the consecutive normal RR intervals and was performed with custom software (Kubios HRV Analysis).
  
  
  RESULTS
  The mean heart rate was higher in ON state compared to SUB state (p = 0.018) and the high-frequency component of the HRV was lower in ON compared to OFF period (p = 0.043). Other HRV parameters values did not significantly differ during the three tested periods.
  
  
  CONCLUSIONS
  Spinal cord stimulation in chronic pain seems to be accompanied by reduced parasympathetic tone, unlike SCS in angina pectoris where previous studies found a reduced cardiac sympathetic tone. Our study might lead to understand the mechanism of action of SCS We investigated a relatively small number of patients, which is the main limitation of our study. Thus, further studies with larger number of patients are required for validation of our results.
authors.affiliation: Department of Neurology, Medical School, University of Pécs, Pécs.
authors.forename: Zsuzsanna
authors.initials: Z
authors.lastname: Kalmár
authors.forename: Norbert
authors.initials: N
authors.lastname: Kovács
authors.forename: István
authors.initials: I
authors.lastname: Balás
authors.forename: Gábor
authors.initials: G
authors.lastname: Perlaki
authors.forename: Eniko
authors.initials: E
authors.lastname: Plózer
authors.forename: Gergely
authors.initials: G
authors.lastname: Orsi
authors.forename: Anna
authors.initials: A
authors.lastname: Altbacker
authors.forename: Attila
authors.initials: A
authors.lastname: Schwarcz
authors.forename: László
authors.initials: L
authors.lastname: Hejjel
authors.forename: Sámuel
authors.initials: S
authors.lastname: Komoly
authors.forename: József
authors.initials: J
authors.lastname: Janszky
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000787:Angina Pectoris / Q000503:physiopathology / Q000628:therapy; D059350:Chronic Pain / Q000503:physiopathology* / Q000628:therapy*; D005260:Female; D006321:Heart / Q000503:physiopathology; D006339:Heart Rate; D006801:Humans; D008297:Male; D008875:Middle Aged; D010275:Parasympathetic Nervous System / Q000503:physiopathology; D018401:Sample Size; D062187:Spinal Cord Stimulation