title: Head-up tilt induced syncope and adenosine A2A receptor gene polymorphism.
abstract: OBJECTIVE
  High adenosine plasma levels and high expression of adenosine A(2A) receptors are observed in patients with unexplained syncope and a positive head-up tilt test (HUT). This study aimed to evaluate the single nucleotide polymorphism (SNP) (c.1364 T>C) which is the most commonly found polymorphism in the A(2A) receptor gene, in patients with unexplained syncope undergoing HUT.
  
  
  RESULTS
  One hundred and five patients with unexplained syncope who underwent HUT were included. Fifty-two had a positive test. Receptor genotype determinations were performed in patients and in 121 healthy subjects. Genotype (TT, CC, TC) was determined from DNA leucocytes. The distribution of the polymorphism showed significant (P < 0.0001) difference when the results of HUT were analysed. Fifty-two per cent of patients with a positive HUT had a CC genotype and 34.6% a TC genotype, whereas 13.2% of the patients with a negative HUT had a CC genotype and 71.7% a TC genotype. Patients with a CC genotype had a higher incidence of spontaneous syncopal episodes.
  
  
  CONCLUSIONS
  In patients with unexplained syncope, a significant association between high incidence of syncopal episodes, positive HUT, and the presence of the CC variant in the adenosine A(2A) receptor gene was elicited.
authors.affiliation: Division of Cardiology, Hôpital Nord and School of Medicine, University of Méditerranée, 13326 Marseille Cedex 15, France.
authors.forename: Alain Y
authors.initials: AY
authors.lastname: Saadjian
authors.forename: Victoria
authors.initials: V
authors.lastname: Gerolami
authors.forename: Roch
authors.initials: R
authors.lastname: Giorgi
authors.forename: Laurence
authors.initials: L
authors.lastname: Mercier
authors.forename: Jean-Louis
authors.initials: JL
authors.lastname: Berge-Lefranc
authors.forename: Franck
authors.initials: F
authors.lastname: Paganelli
authors.forename: Zouher
authors.initials: Z
authors.lastname: Ibrahim
authors.forename: Youlet
authors.initials: Y
authors.lastname: By
authors.forename: Jean Louis
authors.initials: JL
authors.lastname: Guéant
authors.forename: Samuel
authors.initials: S
authors.lastname: Lévy
authors.forename: Régis P
authors.initials: RP
authors.lastname: Guieu
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D005260:Female; D020022:Genetic Predisposition to Disease / Q000235:genetics; D005838:Genotype; D006801:Humans; D008297:Male; D008875:Middle Aged; D020641:Polymorphism, Single Nucleotide / Q000235:genetics*; D043705:Receptor, Adenosine A2A / Q000235:genetics*; D013575:Syncope / Q000235:genetics*; D018667:Tilt-Table Test; D055815:Young Adult
chemical_list: D043705:Receptor, Adenosine A2A