title: Vasovagal syncope: state or trait?
abstract: OBJECTIVE
  The absence of a satisfactory comprehensive theory for vasovagal syncope has prompted attention towards a possible genetic origin. There are several features of this trait that suggest a genetic origin. The purposes of this review are to present a rationale for considering a genetic origin and critically summarize recent findings.
  
  
  RESULTS
  Key characteristics that suggest a genetic origin are incomplete effect in the population, a persistent clinical phenotype, and the absence of obvious infectious or autoimmune causes. There are familial pedigrees of vasovagal syncope, and statistical analyses of the impact of family history on the likelihood of an individual fainting that suggest an autosomal dominant transmission with incomplete penetrance. There is also evidence of sex-specific penetrance. Early candidate gene studies point towards involvement of sympathetic signal transduction in the physiologic cascade.
  
  
  CONCLUSIONS
  Several epidemiologic characteristics of vasovagal syncope suggest that it may have a genetic origin.
authors.affiliation: Libin Cardiovascular Institute of Alberta, University of Calgary, Calgary, Alberta, Canada.
authors.forename: Anna Serletis
authors.initials: AS
authors.lastname: Bizios
authors.forename: Robert S
authors.initials: RS
authors.lastname: Sheldon
mesh_terms: D020022:Genetic Predisposition to Disease; D006801:Humans; D040582:Inheritance Patterns; D010375:Pedigree; D011110:Polymorphism, Genetic; D019462:Syncope, Vasovagal / Q000453:epidemiology / Q000235:genetics*