title: Bedside autonomic function testing in patients with vasovagal syncope.
abstract: The factors that determine the individual susceptibility to vasovagal syncope (VVS) are largely unknown, including the role of the autonomic nervous system. We therefore studied common vagal and sympathetic reflexes in 12 patients with VVS (mean age 37 (18-75) years, 6 men). The Valsalva maneuver and deep breathing were performed to assess vagal responsiveness and mental arithmetic stress; the cold-pressor test and isometric handgrip were performed to assess sympathetic responsiveness. Standing up was performed to assess the combined responsiveness. With the exception of a subnormal response to deep breathing in one patient, all vagal tests were normal. In contrast, the response to mental stress, the cold-pressor test, and isometric handgrip was subnormal in 4 patients, 6 patients, and 4 patients, respectively. The response to standing up was normal in all patients. It is concluded that many patients with VVS are characterized by normal vagal responsiveness, but sympathetic hyporesponsiveness. Sympathetic hyporesponsiveness might explain the inadequate vasoconstruction, which plays an important, early role in VVS.
authors.affiliation: Department of Cardiology, University Hospital Groningen, The Netherlands.
authors.lastname: van den Berg
authors.forename: A J
authors.initials: AJ
authors.lastname: Smit
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D001341:Autonomic Nervous System / Q000503:physiopathology*; D001794:Blood Pressure / Q000502:physiology; D003080:Cold Temperature; D004198:Disease Susceptibility; D005260:Female; D018737:Hand Strength / Q000502:physiology; D006339:Heart Rate / Q000502:physiology; D006801:Humans; D007537:Isometric Contraction / Q000502:physiology; D008297:Male; D008875:Middle Aged; D019095:Point-of-Care Systems; D011187:Posture / Q000502:physiology; D012018:Reflex / Q000502:physiology; D012119:Respiration / Q000502:physiology; D016683:Supine Position / Q000502:physiology; D013564:Sympathetic Nervous System / Q000503:physiopathology; D019462:Syncope, Vasovagal / Q000503:physiopathology*; D013850:Thinking / Q000502:physiology; D014630:Vagus Nerve / Q000503:physiopathology; D014636:Valsalva Maneuver / Q000502:physiology; D014661:Vasoconstriction / Q000502:physiology