title: Role of nitric oxide in young patients with vasovagal syncope.
abstract: OBJECTIVE
  Nitric oxide (NO) formed in the vascular endothelium produces, among other effects, a strong vasodilation. In order to evaluate the possible role of NO in hypotension induced by head-up tilt test (HUT), we measured plasma levels of its metabolites, nitrites and nitrates (NOx), during the test.
  
  
  RESULTS
  Twelve patients with vasovagal syncope and positive HUT [HUT(+)] (mean age: 23+/-5 years) and 13 healthy volunteers with negative HUT (controls) (mean age: 24+/-5 years) were included. Venous blood samples were obtained during the baseline stage for biochemical measurements. Plasma values of NOx were obtained under baseline conditions (T0), at the end of the HUT (T1), and 15 min after the end of the HUT (T2). The baseline biochemical values as well as haemodynamic parameters were similar in HUT(+) patients and controls. NOx plasma values (in micromol/L) were as follows [HUT(+) vs. controls]: T0: 5.7+/-1.6 vs. 8.8+/-4.7 (P=0.05), T1: 6.1+/-3.2 vs. 8.5+/-3.6 (P=NS), and T2: 6.1+/-3 vs. 10.2+/-8.9 (P=NS). The NOx levels were directly correlated with the insulin levels (Spearman's R=0.53, P=0.008).
  
  
  CONCLUSIONS
  Baseline plasma levels of NOx were significantly lower in HUT(+) patients than in controls. However, since the expected increase in NOx values during HUT-induced syncope was not observed, the possible role of NO in vasovagal hypotension is uncertain.
authors.affiliation: Cardiology Department, Hospital de Agudos Juan A. Fernandez, Santa Rosa 2575, Florida (1602), and Facultad de Ingenieria, Universidad de Buenos Aires, Buenos Aires, Argentina. auroruiz@fibertel.com.ar
authors.forename: Graciela Aurora
authors.initials: GA
authors.lastname: Ruiz
authors.forename: Silvina
authors.initials: S
authors.lastname: Sinigaglia
authors.forename: Ricardo
authors.initials: R
authors.lastname: Hermes
authors.forename: Raul
authors.initials: R
authors.lastname: Chirife
authors.forename: Marina
authors.initials: M
authors.lastname: Cápula
authors.forename: Juan Carlos
authors.initials: JC
authors.lastname: Perfetto
authors.forename: María Cristina
authors.initials: MC
authors.lastname: Tentori
authors.forename: Hugo
authors.initials: H
authors.lastname: Grancelli
authors.forename: Martin
authors.initials: M
authors.lastname: Nogues
mesh_terms: D000328:Adult; D005260:Female; D006801:Humans; D008297:Male; D009569:Nitric Oxide / Q000097:blood*; D019462:Syncope, Vasovagal / Q000097:blood* / Q000175:diagnosis*; D018667:Tilt-Table Test
chemical_list: D009569:Nitric Oxide