title: Relationship between sympathetic activity and pain intensity in fibromyalgia.
abstract: OBJECTIVE
  Fibromyalgia (FM) is a syndrome characterised by chronic musculoskeletal pain, hyperalgesia on specific areas of tenderness (tender points) and by an autonomic nervous system dysfunction consistent with sympathetic overactivity. It is not known whether there is any relationship between the amount of cardiovascular sympathetic activity and the magnitude of pain. Our objective was to assess this potential relationship in patients with FM.
  
  
  METHODS
  Electrocardiogram, finger blood pressure, respiration and post-ganglionic sympathetic discharge activity (muscle sympathetic nerve activity, MSNA) were continuously recorded at rest in 25 patients with primary FMS. The autonomic profile was assessed by MSNA and spectral indices of cardiac sympathetic (LFRR) and vagal (HFRR) modulation and of sympathetic vasomotor control (LF-SAP) computed by spectrum analysis of RR and systolic arterial pressure (SAP) variability. Cardiac baroreflex function was evaluated by the index α (αLF). Baroreceptor modulation of the sympathetic vasomotor control (sBRS) was assessed by the MSNA/diastolic pressure relationship.
  
  
  RESULTS
  Pain intensity was linearly correlated with LFRR/HFRR (r² = 0.21; p=0.03), LFSAP (r² = 0.26; p=0.02) and MSNA (burst rate) (r² = 0.45; p=0.003). Pain intensity was inversely correlated with the αLF index (r² = 0.24; p=0.02) and the sBRS (r² = 0.28; p=0.03). Thus, the higher the sympathetic drive to the heart and vessels, the higher the magnitude of chronic pain. Also, the gains of both the cardiac and MSNA baroreceptor control were inversely related to the pain intensity.
  
  
  CONCLUSIONS
  These findings raise the theoretical possibility that in FM patients the use of anti-adrenergic agents might lessen chronic pain intensity by reducing the underlying excessive sympathetic activity.
authors.affiliation: Department of Physical Therapy, Federal University of Sao Carlos, Sao Carlos, Brazil.
authors.forename: Antonio Roberto
authors.initials: AR
authors.lastname: Zamunér
authors.affiliation: Internal Medicine, BIOMETRA Department, Humanitas Clinical and Research Centre, Rozzano, Italy.
authors.forename: Franca
authors.initials: F
authors.lastname: Barbic
authors.affiliation: Internal Medicine, BIOMETRA Department, Humanitas Clinical and Research Centre, Rozzano, Italy.
authors.forename: Franca
authors.initials: F
authors.lastname: Dipaola
authors.affiliation: Internal Medicine, BIOMETRA Department, Humanitas Clinical and Research Centre, Rozzano, Italy.
authors.forename: Mara
authors.initials: M
authors.lastname: Bulgheroni
authors.affiliation: Emergency Medicine, Legnano Hospital, Legnano, Italy.
authors.forename: Alessandro
authors.initials: A
authors.lastname: Diana
authors.affiliation: IRCCS Galeazzi Orthopaedic Institute, Milan, Italy.
authors.forename: Fabiola
authors.initials: F
authors.lastname: Atzeni
authors.affiliation: Department of Anesthesia and Intensive Care Unit, Humanitas Clinical and Research Centre, Rozzano; and Department of Electronics Information and Bioengineering, Politecnico di Milano, Milan, Italy.
authors.forename: Andrea
authors.initials: A
authors.lastname: Marchi
authors.affiliation: Department of Rheumatology, L. Sacco Hospital, Milan, Italy.
authors.forename: Piercarlo
authors.initials: P
authors.lastname: Sarzi-Puttini
authors.affiliation: Department of Biomedical Sciences for Health, IRCCS Galeazzi Orthopaedic Institute, Milan; and University of Milan, Milan, Italy.
authors.forename: Alberto
authors.initials: A
authors.lastname: Porta
authors.affiliation: Internal Medicine, BIOMETRA Department, Humanitas Clinical and Research Centre, Rozzano; and University of Milan, Milan, Italy.
authors.forename: Raffaello
authors.initials: R
authors.lastname: Furlan
mesh_terms: D000328:Adult; D017704:Baroreflex; D001794:Blood Pressure; D001795:Blood Pressure Determination; D002319:Cardiovascular System / Q000294:innervation*; D059350:Chronic Pain / Q000175:diagnosis* / Q000209:etiology / Q000503:physiopathology / Q000523:psychology; D004562:Electrocardiography; D004576:Electromyography; D005260:Female; D005356:Fibromyalgia / Q000150:complications / Q000175:diagnosis* / Q000503:physiopathology / Q000523:psychology; D006339:Heart Rate; D006801:Humans; D016014:Linear Models; D008168:Lung / Q000294:innervation*; D008297:Male; D008875:Middle Aged; D018482:Muscle, Skeletal / Q000294:innervation*; D010147:Pain Measurement; D058748:Pain Perception; D017288:Pain Threshold; D011237:Predictive Value of Tests; D056152:Respiratory Rate; D012720:Severity of Illness Index; D017779:Sympathetic Fibers, Postganglionic / Q000503:physiopathology; D013564:Sympathetic Nervous System / Q000503:physiopathology*