title: The Arg389Gly beta1-adrenergic receptor gene polymorphism and susceptibility to faint during head-up tilt test.
abstract: OBJECTIVE
  To investigate the association of the Gly389 allele with positive head-up tilt test (HUT) in a Mexican Mestizo population.
  
  
  RESULTS
  HUT results were compared between carriers (one or two copies of the Gly389 allele) and non-carriers (Arg389Arg genotype) of the Gly389 allele of the beta(1)AR gene in 50 patients with unexplained syncope. Thirty-three patients (66%) had a positive HUT. Patients with a positive HUT had a higher Gly389 allele frequency compared with those with a negative test (30.3 vs. 3%; OR 13; pC = 0.012). Moreover, when comparing positive HUT in passive drug-free phase, positive HUT in pharmacological (nitrate) phase, and negative (both phases), a decreasing gradient in the frequencies of the Gly389 allele was found among the three groups: 45.4, 22.7, and 3%, respectively.
  
  
  CONCLUSIONS
  An association of positive tilt table testing to a single nucleotide polymorphism with a Gly to Arg switch at position 389 of the beta(1)AR was found. This polymorphism may contribute to susceptibility to faint during orthostatic challenge.
authors.affiliation: Department of Electrocardiology, Instituto Nacional de Cardiología Ignacio Chávez, Mexico City, Mexico.
authors.forename: M F
authors.initials: MF
authors.lastname: Márquez
authors.forename: Guadalupe
authors.initials: G
authors.lastname: Hernández-Pacheco
authors.forename: Antonio G
authors.initials: AG
authors.lastname: Hermosillo
authors.forename: Jorge R
authors.initials: JR
authors.lastname: Gómez
authors.forename: Manuel
authors.initials: M
authors.lastname: Cárdenas
authors.forename: Gilberto
authors.initials: G
authors.lastname: Vargas-Alarcón
mesh_terms: D000328:Adult; D005260:Female; D020022:Genetic Predisposition to Disease / Q000453:epidemiology / Q000235:genetics; D006579:Heterozygote; D006801:Humans; D008297:Male; D008800:Mexico / Q000453:epidemiology; D009154:Mutation; D020641:Polymorphism, Single Nucleotide / Q000235:genetics*; D018342:Receptors, Adrenergic, beta-1 / Q000235:genetics*; D013575:Syncope / Q000175:diagnosis / Q000453:epidemiology* / Q000235:genetics*; D018667:Tilt-Table Test / Q000706:statistics & numerical data*
chemical_list: D018342:Receptors, Adrenergic, beta-1