title: Electrocardiographic QT interval and cardiovascular reactivity in fibromyalgia differ from chronic fatigue syndrome.
abstract: BACKGROUND
  Fibromyalgia (FM) and chronic fatigue syndrome (CFS) frequently overlap clinically and have been considered variants of one common disorder. We have recently shown that CFS is associated with a short corrected electrocardiographic QT interval (QTc). In the present study, we evaluated whether FM and CFS can be distinguished by QTc.
  
  
  METHODS
  The study groups were comprised of women with FM (n=30) and with CFS (n=28). The patients were evaluated with a 10 min supine-30 min head-up tilt test. The electrocardiographic QT interval was corrected for heart rate (HR) according to Fridericia's equation (QTc). In addition, cardiovascular reactivity was assessed based on blood pressure and HR changes and was expressed as the 'hemodynamic instability score' (HIS).
  
  
  RESULTS
  The average supine QTc in FM was 417 ms (SD 25) versus 372 ms (SD 22) in CFS (p<0.0001); the supine QTc cut-off <385.7 ms was 79% sensitive and 87% specific for CFS vs. FM. The average QTc at the 10th minute of tilt was 409 ms (SD 18) in FM versus 367 ms (SD 21) in CFS (p<0.0001); the tilt QTc cut-off <383.3 ms was 71% sensitive and 91% specific for CFS vs. FM. The average HIS in FM patients was -3.52 (SD 1.96) versus +3.21 (SD 2.43) in CFS (p<0.0001).
  
  
  CONCLUSIONS
  A relatively short QTc and positive HIS characterize CFS patients and distinguish them from FM patients. These data may support the contention that FM and CFS are separate disorders.
authors.affiliation: Department of Internal Medicine A, Bnai Zion Medical Center and Rappaport Family Faculty of Medicine, Technion-Israel Institute of Technology, Haifa, Israel. Naschitz@tx.technion.ac.il
authors.forename: Jochanan E
authors.initials: JE
authors.lastname: Naschitz
authors.forename: Gleb
authors.initials: G
authors.lastname: Slobodin
authors.forename: Dauod
authors.initials: D
authors.lastname: Sharif
authors.forename: Madeline
authors.initials: M
authors.lastname: Fields
authors.forename: Hillel
authors.initials: H
authors.lastname: Isseroff
authors.forename: Edmond
authors.initials: E
authors.lastname: Sabo
authors.forename: Itzhak
authors.initials: I
authors.lastname: Rosner
mesh_terms: D000222:Adaptation, Physiological; D000328:Adult; D001794:Blood Pressure; D002319:Cardiovascular System / Q000503:physiopathology*; D003937:Diagnosis, Differential; D004562:Electrocardiography; D015673:Fatigue Syndrome, Chronic / Q000175:diagnosis* / Q000503:physiopathology*; D005260:Female; D005356:Fibromyalgia / Q000175:diagnosis* / Q000503:physiopathology*; D006339:Heart Rate; D006801:Humans; D008875:Middle Aged; D018667:Tilt-Table Test