BIGATED TRANSCRANIAL DOPPLER FOR THE DETECTION OF CLINICALLY SILENT CIRCULATING EMBOLI IN NORMAL PERSONS AND PATIENTS WITH PROSTHETIC CARDIAC VALVES

Background and Purpose Detection of clinically silent circulating micr oemboli by transcranial Doppler sonography is now being widely investi gated in the hope of identifying patients at increased risk for stroke . Automatic detection by bigated Doppler, which uses sampling from two different depths in the artery under study and considers the motion o f the embolus, may help to define ''periods of interest'' that can be evaluated off-line. Methods In 12 normal volunteers and 10 patients wi th prosthetic aortic valves, we performed 1-hour recordings from one m iddle cerebral artery. In the normal subjects, we produced additional artifacts to use them as false-positives. Detection of microemboli was done off-line from digital audiotapes by an experienced blinded inves tigator (used as the gold standard) and was compared with on-line dete ction using specially designed software. Results With the setting used , 91.5% of all recorded artifacts could correctly be identified as suc h with the software. Embolic signals were detected by the software wit h a specificity of 59.9% and a sensitivity of 74.3%. Conclusions Bigat ed Doppler adds a new dimension to the definition and detection of mic roembolic signals. It constitutes an important step forward toward aut omatic screening of stroke-prone patients. Assessing on-line periods o f interest during the recording and going over the recorded data again off-line helps to save time for the discrimination of embolic signals from both the normal Doppler spectrum background and artifacts.