title: Impaired peripheral vasoconstrictor response to orthostatic stress in patients with multiple system atrophy.
abstract: OBJECTIVE
  Most patients with multiple system atrophy (MSA) develop autonomic dysfunction; however, orthostatic hypotension is not always present. Failure of the vasoconstrictor response is thought to be responsible for orthostatic hypotension, but the degree of impairment of this response in patients with MSA is unclear. We assessed autonomic function in patients with MSA by evaluating the vasoconstrictive response during a head-up tilt test and determining its relationship to orthostatic hypotension. As an additional examination, the efficacy of norepinephrine in treating orthostatic hypotension was also assessed.
  
  
  METHODS
  The study included 82 patients with MSA and 28 controls. Measures of total peripheral resistance were obtained during a head-up tilt test. Norepinephrine was administered to the patients lacking a vasoconstrictive response to evaluate its ability to treat orthostatic hypotension.
  
  
  RESULTS
  At a 60° tilt, orthostatic hypotension occurred in 47.6% of the patients and 0% of controls. Reduction in total peripheral resistance from baseline at a 60° tilt was observed in 69.5% of the patients and 0% of controls. In patients with MSA, changes in systolic blood pressure from the baseline at a 60° tilt correlated positively with changes in the total peripheral resistance (r = 0.69, p < 0.0001). Norepinephrine prevented the reduction of total peripheral resistance and development of orthostatic hypotension.
  
  
  CONCLUSIONS
  A large number of patients with MSA with and without orthostatic hypotension have an impaired peripheral vasoconstrictive response, suggesting a high frequency of cardiovascular dysautonomia with an associated risk of developing orthostatic hypotension. A norepinephrine infusion was effective for treating orthostatic hypotension.
authors.affiliation: Department of Neurology, Nagoya University Graduate School of Medicine, 65 Tsurumai-cho Showa-ku Nagoya, 466-8550, Japan.
authors.forename: Junichiro
authors.initials: J
authors.lastname: Suzuki
authors.affiliation: Department of Neurology, Nagoya University Graduate School of Medicine, 65 Tsurumai-cho Showa-ku Nagoya, 466-8550, Japan.
authors.forename: Tomohiko
authors.initials: T
authors.lastname: Nakamura
authors.affiliation: Department of Neurology, Nagoya University Graduate School of Medicine, 65 Tsurumai-cho Showa-ku Nagoya, 466-8550, Japan; Department of Pathophysiological Laboratory Science, Nagoya University Graduate School of Medicine, Nagoya, Japan.
authors.forename: Masaaki
authors.initials: M
authors.lastname: Hirayama
authors.affiliation: Department of Neurology, Nagoya University Graduate School of Medicine, 65 Tsurumai-cho Showa-ku Nagoya, 466-8550, Japan.
authors.forename: Yasuaki
authors.initials: Y
authors.lastname: Mizutani
authors.affiliation: Department of Neurology, Nagoya University Graduate School of Medicine, 65 Tsurumai-cho Showa-ku Nagoya, 466-8550, Japan.
authors.forename: Akinori
authors.initials: A
authors.lastname: Okada
authors.affiliation: Department of Neurology, Nagoya University Graduate School of Medicine, 65 Tsurumai-cho Showa-ku Nagoya, 466-8550, Japan.
authors.forename: Mizuki
authors.initials: M
authors.lastname: Ito
authors.affiliation: Department of Neurology, Nagoya University Graduate School of Medicine, 65 Tsurumai-cho Showa-ku Nagoya, 466-8550, Japan.
authors.forename: Hirohisa
authors.initials: H
authors.lastname: Watanabe
authors.affiliation: Department of Neurology, Nagoya University Graduate School of Medicine, 65 Tsurumai-cho Showa-ku Nagoya, 466-8550, Japan. Electronic address: sobueg@med.nagoya-u.ac.jp.
authors.forename: Gen
authors.initials: G
authors.lastname: Sobue
mesh_terms: D000368:Aged; D001342:Autonomic Nervous System Diseases / Q000188:drug therapy / Q000209:etiology / Q000503:physiopathology; D005260:Female; D006801:Humans; D007024:Hypotension, Orthostatic / Q000188:drug therapy / Q000209:etiology / Q000503:physiopathology; D008297:Male; D008875:Middle Aged; D019578:Multiple System Atrophy / Q000150:complications*; D009638:Norepinephrine / Q000008:administration & dosage / Q000494:pharmacology*; D016896:Treatment Outcome; D014662:Vasoconstrictor Agents / Q000008:administration & dosage / Q000494:pharmacology*
chemical_list: D014662:Vasoconstrictor Agents; D009638:Norepinephrine
keywords: Head-up tilt test; Impaired vasoconstrictor response; Multiple system atrophy; Orthostatic hypotension; Peripheral resistance