title: M-wave analysis and passive tilt in patients with different degrees of carotid artery disease.
abstract: OBJECTIVE
  Carotid artery disease (CAD) is able to critically impair cerebral autoregulation which increases the risk for stroke. As therapeutic strategy largely depends on the degree of CAD, we investigated whether this gradation is also related to significant changes in autoregulatory capacity. We applied cross-spectral analysis (CSA) of spontaneous Mayer-wave (M-wave) oscillations and passive tilting (PT) to test cerebral autoregulation.
  
  
  METHODS
  Cerebral autoregulation was tested in 102 patients with carotid stenosis (> or =70%) or occlusion and 14 controls by comparison of continuous transcranial Doppler sonography of the middle cerebral artery and beat-to-beat arterial blood pressure (ABP) during PT to 80 degrees head-up position as well as by CSA of M-waves (3-9 cpm).
  
  
  RESULTS
  The orthostatic decrease of cerebral blood flow velocity (CBFV) was not correlated with the degree of CAD and showed a lower sensitivity and specificity than phase angle shifts between M-waves in ABP and CBFV (sensitivity: 75-80%, specificity: 86%). Phase angles were gradually lowered in carotid stenoses > 70%, but apparently, they were only moderately correlated with the degree of CAD (r = -0.35, P < 0.01). An additional influencing factor seemed to be the sufficiency of collateralization.
  
  
  CONCLUSIONS
  The results show that CSA of M-waves is more appropriate for testing autoregulation than PT. CSA suggests that the capacity to autoregulate depends to a certain extent on the degree of CAD but is also influenced by the sufficiency of collateral pathways and pre-existing strokes.
authors.affiliation: Departments of Neurology Neuroradiology, University Hospital Aachen, Aachen, Germany. christina.haubrich@t-online.de
authors.forename: C
authors.initials: C
authors.lastname: Haubrich
authors.forename: A
authors.initials: A
authors.lastname: Klemm
authors.forename: R R
authors.initials: RR
authors.lastname: Diehl
authors.forename: W
authors.initials: W
authors.lastname: Möller-Hartmann
authors.forename: C
authors.initials: C
authors.lastname: Klötzsch
mesh_terms: D000328:Adult; D000368:Aged; D001783:Blood Flow Velocity / Q000502:physiology; D001794:Blood Pressure / Q000502:physiology; D001921:Brain / Q000098:blood supply*; D002343:Carotid Artery, Internal / Q000000981:diagnostic imaging; D016893:Carotid Stenosis / Q000000981:diagnostic imaging* / Q000503:physiopathology; D002544:Cerebral Infarction / Q000000981:diagnostic imaging* / Q000503:physiopathology; D004292:Dominance, Cerebral / Q000502:physiology; D005260:Female; D005583:Fourier Analysis; D006706:Homeostasis / Q000502:physiology*; D006801:Humans; D007091:Image Processing, Computer-Assisted; D020244:Infarction, Middle Cerebral Artery / Q000000981:diagnostic imaging / Q000503:physiopathology; D008297:Male; D008875:Middle Aged; D012016:Reference Values; D012307:Risk Factors; D018667:Tilt-Table Test; D018615:Ultrasonography, Doppler, Color; D017585:Ultrasonography, Doppler, Transcranial