title: Vasovagal syncope.
abstract: BACKGROUND
  Vasovagal syncope is the most common type of syncope and is one of the most difficult types to manage.
  
  
  OBJECTIVE
  This article reviews the status of mechanisms, diagnosis, and management of vasovagal syncope.
  
  
  METHODS
  MEDLINE search for English-language and German-language articles on vasovagal syncope published up to June 1999.
  
  
  METHODS
  Case reports and series, clinical trials, research investigations, and review articles from peer-reviewed journals.
  
  
  METHODS
  Findings were summarized and discussed individually. Summaries were made in table format. Statistical analysis of combined data was inappropriate because of differences among studies in patient selection, testing, and follow-up.
  
  
  RESULTS
  The population of patients with vasovagal syncope is highly heterogeneous. Triggers of vasovagal syncope are likely to be protean, and many potential central and peripheral triggers have been identified. The specific mechanisms underlying the interactions among decreased preload, sympathetic and parasympathetic modulation, vasodilation, and cardioinhibition remain unknown. Tilt-table testing is a widely used diagnostic tool. The test results should be interpreted in the context of patients' clinical presentations and with an understanding of the sensitivity and specificity of the test. Assessment of therapeutic outcomes has been difficult, primarily because of patient heterogeneity, the large number of pharmacologic agents available for therapy, and the sporadic nature of the syndrome complex.
  
  
  CONCLUSIONS
  Vasovagal syncope is a common clinical syndrome that has complex and variable mechanisms and is difficult to manage. Advancements are being made in laboratory investigations of its triggering mechanisms. Randomized, controlled trials of pharmacologic and nonpharmacologic interventions are needed. Mechanism-targeted therapeutic trials may improve clinical outcomes.
authors.affiliation: Mayo Clinic, 200 First Street SW, Rochester, MN 55905, USA.
authors.forename: A M
authors.initials: AM
authors.lastname: Fenton
authors.forename: S C
authors.initials: SC
authors.lastname: Hammill
authors.forename: R F
authors.initials: RF
authors.lastname: Rea
authors.forename: P A
authors.initials: PA
authors.lastname: Low
authors.forename: W K
authors.initials: WK
authors.lastname: Shen
mesh_terms: D000818:Animals; D001341:Autonomic Nervous System / Q000503:physiopathology; D001794:Blood Pressure / Q000502:physiology; D006801:Humans; D010808:Physical Examination; D017410:Practice Guidelines as Topic; D015203:Reproducibility of Results; D019462:Syncope, Vasovagal / Q000175:diagnosis / Q000209:etiology / Q000503:physiopathology / Q000628:therapy; D018667:Tilt-Table Test; D014630:Vagus Nerve / Q000503:physiopathology