title: Sympathetic and cardiac baroreflex function in panic disorder.
abstract: BACKGROUND
  Recent reports have demonstrated increased cardiac risk, and an association with essential hypertension in patients with panic disorder. The cause is not known, but possibly involves sympathetic nervous activation. In this study, we evaluated the arterial baroreflex control of vascular sympathetic nervous outflow and cardiac baroreflex function in panic disorder patients.
  
  
  RESULTS
  We studied nine patients suffering from panic disorder and ten healthy subjects. Microneurographic recording of muscle sympathetic nerve activity (MSNA) was made with simultaneous recording of blood pressure (BP) and electrocardiogram (ECG). The relationship between MSNA and spontaneous diastolic BP (DBP) changes was assessed at rest and was defined as the arterial baroreflex control of MSNA. Cardiac baroreflex function was assessed using the sequence method. Anxiety was assessed using Spielberger's anxiety state and trait inventory. The slopes of the relationship between MSNA and DBP were more negative (steeper) in the panic disorder group compared with the control subjects (-5.97 +/- 0.45 versus -3.06 +/- 0.43 bursts/100 heart beats per mmHg, P < 0.001). Panic disorder patients had significantly higher state and trait anxiety scores. The slope of the relationship between MSNA and diastolic BP was significantly related to the trait anxiety of the subjects. There was no difference between the cardiac baroreflex sensitivity between the two groups.
  
  
  CONCLUSIONS
  Patients with panic disorder exhibit enhanced reflex gain of the arterial baroreflex control of MSNA but no change in the cardiac baroreflex. While any clinical significance this observation might have in relation to increased cardiac risk in panic disorder, or to concordance with essential hypertension, remains to be elucidated, increased reactivity of vasoconstricting sympathetic nerves may be a trait characteristic in this cohort.
authors.affiliation: Human Neurotransmitter Laboratory, Baker Heart Research Institute, PO Box 6492, St Kilda Road Central, Melbourne, Victoria 8008, Australia. elisabeth.lambert@baker.edu.au
authors.forename: Elisabeth A
authors.initials: EA
authors.lastname: Lambert
authors.forename: Jane
authors.initials: J
authors.lastname: Thompson
authors.forename: Markus
authors.initials: M
authors.lastname: Schlaich
authors.forename: Dominique
authors.initials: D
authors.lastname: Laude
authors.forename: Jean-Luc
authors.initials: JL
authors.lastname: Elghozi
authors.forename: Murray D
authors.initials: MD
authors.lastname: Esler
authors.forename: Gavin W
authors.initials: GW
authors.lastname: Lambert
mesh_terms: D000328:Adult; D001007:Anxiety; D001158:Arteries / Q000503:physiopathology; D017704:Baroreflex; D001794:Blood Pressure; D016022:Case-Control Studies; D003971:Diastole; D005260:Female; D006321:Heart / Q000503:physiopathology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D009132:Muscles / Q000294:innervation; D016584:Panic Disorder / Q000503:physiopathology* / Q000523:psychology; D013564:Sympathetic Nervous System / Q000503:physiopathology*