Automated identification of Doppler microembolic signals: comparison of two techniques.

An alternative technique for identification of Doppler microemboli signals (MES), based on intensity measurements in the vessel and in an arbitrary sample volume was recently reported. We evaluated the applicability of this approach as stand alone system, and compared it to the standard bigate method (TCD 8, version 8T). Bilateral TCD monitoring was performed in 11 patients with prosthetic heart valves and 15 patients during elective cardiac surgery, using three sample volumes (29 mm, 50 mm and 55 mm). All data was saved on digital audio tapes and evaluated by two experienced observers. Only signals unanimously identified as MES or artifacts by both observers were evaluated. A total of 6189 MES and 11,241 artifacts were further analysed. Sensitivity and specificity of the bigate approach and the technique utilising the arbitrary sample volume were 90.7%, 91.3% and 88%, 91.9% respectively. Simultaneous monitoring over three sample volumes and combination of the two detection algorithms could potentially provide an adequate stand-alone system for MES detection.