title: Identification of Doppler microembolic signals with a bigate probe in patients with prosthetic heart valves.
abstract: OBJECTIVE
  The applicability of a bigate probe, simultaneously harvesting two spatially separated vessel segments, in the identification of Doppler microembolic signals (MES) was evaluated.
  
  
  METHODS
  One hundred and ninety-seven patients with artificial heart valves were bilaterally monitored over two segments of each middle cerebral artery, with a minimal distance of 5 mm between them, using 2 MHz probes. Time delay in the appearance of high intensity transients between the two segments was calculated off-line, using dedicated software, integrated in the Doppler device.
  
  
  RESULTS
  Bigate monitoring was feasible in 96% of patients. MES prevalence and counts were 37% and 26 (18-44) respectively. All but 8.8% of the 2932 MES signals recorded appeared in both Doppler channels, with a time delay of 4.4 (4.2-4.7) msec (range between 0 and 34 msec). Time delay in 97% of artifact signals was under 1 msec. Application of 1 msec as low and 20 msec as high cut-off point between MES and artifacts resulted in the correct identification of 97% of artifacts and 89.6% of MES.
  
  
  CONCLUSIONS
  The multigate approach is a reliable method for identification of Doppler microembolic signals in patients with prosthetic heart valves. The value of this technique in other patient groups remains to be evaluated.
authors.affiliation: Department of Neurology, Martin-Luther University of Halle-Wittenberg, Ernst-Grube Str 40, Halle/Saale D-06097, Germany.
authors.forename: A
authors.initials: A
authors.lastname: Lindner
authors.forename: D
authors.initials: D
authors.lastname: Georgiadis
authors.forename: G
authors.initials: G
authors.lastname: Fischer
authors.forename: H R
authors.initials: HR
authors.lastname: Zerkowski
authors.forename: S
authors.initials: S
authors.lastname: Zierz
mesh_terms: D001021:Aortic Valve; D002536:Cerebral Arteries / Q000000981:diagnostic imaging* / Q000473:pathology; D005260:Female; D006350:Heart Valve Prosthesis; D006801:Humans; D002542:Intracranial Embolism and Thrombosis / Q000000981:diagnostic imaging* / Q000453:epidemiology*; D008297:Male; D008875:Middle Aged; D008943:Mitral Valve; D015995:Prevalence; D017585:Ultrasonography, Doppler, Transcranial