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Identification of Doppler microembolic signals with a bigate probe in patients with prosthetic heart valves
A Lindner1, D Georgiadis, G Fischer
1Department of Neurology, Martin-Luther University of Halle-Wittenberg, Ernst-Grube Str 40, Halle/Saale D-06097, Germany.
Background And Purpose:
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.