title: Endothelial function and peripheral vasomotion in the brachial artery in neurally mediated syncope.
abstract: BACKGROUND
  Paradoxical peripheral vasodilation is one of the suspected mechanisms of neurally mediated syncope. Parasympathetic stimulation following sympathetic activation during orthostatic stress mainly contributes to this vasodilation.
  
  
  OBJECTIVE
  Since endothelial function modulates peripheral vascular tone, this study aimed to determine whether endothelial function and inappropriate peripheral vasomotion has a significant role in the pathogenesis of neurally mediated syncope.
  
  
  METHODS
  To investigate whether endothelial function is augmented or whether abnormal peripheral vasomotion exits, flow-mediated dilation (FMD, endothelium-dependent vasodilation) and sublingual glyceryl trinitrate-induced dilation (0.3 mg, GTN-D, endothelium-independent vasodilation) were measured in the brachial artery in 16 patients with neurally mediated syncope, aged 33 +/- 10 years, by using high-resolution ultrasound. All patients underwent positive head-up tilt testing. These measures were compared with those in 16 control subjects matched with the patients by age, gender, and coronary risk factors. For FMD, percent diameter changes were obtained from baseline to hyperemic conditions (1 min after 5 min occlusion of the forearm artery). There were five smokers in both the patient and the control groups, but there was no structural heart disease in either group.
  
  
  RESULTS
  Baseline brachial artery diameters were comparable (3.8 +/- 0.6 vs. 3.8 +/- 0.7 mm, NS). Flow-mediated dilation in patients with neurally mediated syncope had a normal value of 9.8 +/- 5.0% despite the inclusion of five smokers. Flow-mediated dilation and GTN-D in patients with neurally mediated syncope were significantly greater than those in controls (9.0 +/- 5.0 vs. 3.0 +/- 3.5%, p<0.05; 18.4 +/- 5.5 vs. 14.1 +/- 4.4%, p<0.05).
  
  
  CONCLUSIONS
  Augmented endothelial function and/or abnormal peripheral vasomotion in peripheral arteries are important in patients with neurally mediated syncope in selected populations.
authors.affiliation: National Defense Medical College, Internal Medicine-1, Tokorozawa, Saitama, Japan.
authors.forename: B
authors.initials: B
authors.lastname: Takase
authors.forename: T
authors.initials: T
authors.lastname: Akima
authors.forename: A
authors.initials: A
authors.lastname: Uehata
authors.forename: S
authors.initials: S
authors.lastname: Katushika
authors.forename: K
authors.initials: K
authors.lastname: Isojima
authors.forename: K
authors.initials: K
authors.lastname: Satomura
authors.forename: F
authors.initials: F
authors.lastname: Ohsuzu
authors.forename: A
authors.initials: A
authors.lastname: Kurita
mesh_terms: D000328:Adult; D001916:Brachial Artery / Q000502:physiology*; D003627:Data Interpretation, Statistical; D004730:Endothelium, Vascular / Q000502:physiology*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D005996:Nitroglycerin; D012907:Smoking / Q000009:adverse effects; D019462:Syncope, Vasovagal / Q000175:diagnosis / Q000209:etiology / Q000503:physiopathology*; D018667:Tilt-Table Test; D014664:Vasodilation / Q000502:physiology; D014665:Vasodilator Agents; D014666:Vasomotor System / Q000502:physiology*
chemical_list: D014665:Vasodilator Agents; D005996:Nitroglycerin