Variability of velocity and duration of microembolic signals detected by bigated transcranial Doppler sonography in carotid endarterectomy.
OBJECTIVE
To differentiate between gaseous and particular microemboli in carotid surgery one clinical approach is the interpretation of the effective sample volume length (SVL). We investigated whether such a clinical interpretation is based on reproducible measurements.


METHODS
Microembolic signals (MES) recorded during carotid endarterectomy by a bigated transcranial Doppler device were analyzed off-line. In the two sample volumes, the duration and the velocity of the MES were measured by two observers independently from each other twice within 2 weeks. The SVL of the MES were calculated by multiplying duration with velocity.


RESULTS
In the anatomical proximal sample volume 215 MES were recorded of which 203 (94.5%) were also present in the distal. The SVL medians of the MES were 2.2-4.1 mm lower in the distal than in the proximal sample volume as a result of lower velocity and shorter duration of the MES in the distal sample volume. The median of the paired differences of the SVL was 0.2 mm (interquartile range: 0.0-1.2) in the proximal sample volume and 0.8 mm (0.2-1.8) in the distal sample volume for observer 1, and 0.6 mm (0.4-2.2) and 0.9 mm (0.5-1.6) for observer 2. The median of the paired differences of the SVL between the observers was 1.4 mm (1.2-2.9) in the proximal sample volume and 1.6 mm (1.3-3.0) in the distal.


CONCLUSIONS
The intra- and interobserver agreement on calculating SVL is good. However, the depth of insonation influences some features of embolic signals.
Müller
M
M
Department of Neurology, University Hospital of the Saarland, Oscar-Orth-Strasse 3, D-66421 Homburg/Saar, Germany.
Pan
X
X
Walter
P
P
Schimrigk
K
K
D000368:Aged; D002341:Carotid Artery Thrombosis / Q000000981:diagnostic imaging* / Q000601:surgery; D002343:Carotid Artery, Internal / Q000000981:diagnostic imaging; D016894:Endarterectomy, Carotid; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008297:Male; D008875:Middle Aged; D016343:Monitoring, Intraoperative / Q000379:methods*; D015588:Observer Variation; D015203:Reproducibility of Results; D017585:Ultrasonography, Doppler, Transcranial; D014741:Video Recording