title: Muscle ischaemia in patients with orthostatic hypotension assessed by velocity recovery cycles.
abstract: OBJECTIVE
  Patients with orthostatic hypotension may experience neck pain radiating to the occipital region of the skull and the shoulders while standing (so-called coat-hanger ache). This study assessed muscle membrane potential in the trapezius muscle of patients with orthostatic hypotension and healthy subjects during head-up tilt (HUT), by measuring velocity recovery cycles (VRCs) of muscle action potentials as an indicator of muscle membrane potential.
  
  
  METHODS
  Eight patients with multiple system atrophy (MSA), orthostatic hypotension and a positive history for coat-hanger pain and eight normal controls (NCs) were included in this study. Repeated VRCs were recorded from the trapezius muscle by direct muscle stimulation in the supine position and during HUT for 10 min.
  
  
  RESULTS
  Muscle VRC recordings did not differ between MSA patients and NCs in the supine position. During HUT, early supernormality decreased progressively and relative refractory period increased in MSA patients whereas VRC measures remained unchanged in NCs. Ten minutes after the start of HUT, early supernormality was reduced by 44% and relative refractory period was increased by 17%.
  
  
  CONCLUSIONS
  Muscle membranes in patients with orthostatic hypotension become progressively depolarised during standing. Membrane depolarisation is most likely the result of muscle ischaemia, related to the drop in perfusion pressure caused by orthostatic hypotension. Coat-hanger ache is most likely a consequence of this muscle ischaemia.
authors.affiliation: Department of Neurology, Inselspital, Bern University Hospital and University of Bern, Bern, Switzerland.
authors.forename: Andrea Monika
authors.initials: AM
authors.lastname: Humm
authors.forename: Hugh
authors.initials: H
authors.lastname: Bostock
authors.forename: Rebekka
authors.initials: R
authors.lastname: Troller
authors.forename: Werner Josef
authors.initials: WJ
authors.lastname: Z'Graggen
mesh_terms: D000200:Action Potentials / Q000502:physiology; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D016022:Case-Control Studies; D005260:Female; D006801:Humans; D007024:Hypotension, Orthostatic / Q000150:complications / Q000503:physiopathology*; D007511:Ischemia / Q000150:complications / Q000503:physiopathology*; D008297:Male; D008875:Middle Aged; D019578:Multiple System Atrophy / Q000150:complications / Q000503:physiopathology; D018482:Muscle, Skeletal / Q000503:physiopathology*; D019547:Neck Pain / Q000150:complications / Q000503:physiopathology*; D018667:Tilt-Table Test / Q000379:methods / Q000706:statistics & numerical data