title: Exaggerated beat-to-beat R amplitude variability in patients with panic disorder after intravenous isoproterenol.
abstract: BACKGROUND
  Anxiety symptoms are associated with a marked increase in sudden cardiac death, suggesting an abnormality in cardiac autonomic function. Our previous studies show a relationship between R amplitude variability and sympathetic function.
  
  
  METHODS
  We examined the effects of beta-adrenergic stimulation on R and T amplitude variability in panic disorder patients by infusing the beta-adrenergic agonist isoproterenol in 6 panic disorder patients and 11 normal subjects. The ECG signal was analyzed before the infusion and 5 min after the infusion was started. The outcome measures were the R and T detrended variance normalized for mean amplitudes (R(vm) and T(vm)) and the R(vi) and T(vi), measures which are normalized for the inter-beat interval variability in addition.
  
  
  RESULTS
  Patients with panic disorder had significantly more variability in R and T amplitude than normal controls and the R amplitude variability was increased further by beta-adrenergic stimulation with isoproterenol, which was more pronounced in the patients.
  
  
  CONCLUSIONS
  The isoproterenol-associated increase in R amplitude variability occurred in controls in the absence of significant anxiety. However, the increase in R amplitude variability was greater in patients with panic disorder, suggesting a greater sensitivity to beta-adrenergic effects of isoproterenol or to isoproterenol-induced anxiety.
authors.affiliation: Department of Psychiatry and Behavioral Neurosciences, Wayne State University School of Medicine, Detroit, Michigan, USA. vikramyershr@yahoo.com
authors.forename: Vikram K
authors.initials: VK
authors.lastname: Yeragani
authors.forename: Robert
authors.initials: R
authors.lastname: Pohl
authors.forename: Karl-Jürgen
authors.initials: KJ
authors.lastname: Bär
authors.forename: Pratap
authors.initials: P
authors.lastname: Chokka
authors.forename: Manuel
authors.initials: M
authors.lastname: Tancer
mesh_terms: D000318:Adrenergic beta-Agonists / Q000627:therapeutic use*; D000328:Adult; D000704:Analysis of Variance; D004562:Electrocardiography; D005260:Female; D006329:Heart Conduction System / Q000187:drug effects* / Q000503:physiopathology; D006339:Heart Rate / Q000187:drug effects* / Q000502:physiology; D006801:Humans; D007275:Injections, Intravenous / Q000379:methods; D007545:Isoproterenol / Q000627:therapeutic use*; D008297:Male; D016584:Panic Disorder / Q000188:drug therapy* / Q000503:physiopathology*
chemical_list: D000318:Adrenergic beta-Agonists; D007545:Isoproterenol