W. Mess
University Hospital – Maastricht, Netherlands
It has been shown for different patient categories that the detection of microembolic signals (MES) in the middle cerebral artery helps to estimate the risk of future cerebrovascular events. The strength of the evidence for this relationship differs for the different clinical situations. So, the question whether automated MES detection should be applied in the daily clinical context depends not only on the adequacy of the detection system. However, a properly functional system is a prerequisite for its succesful clinical application. This comprises not only the correct identification of MES in the transcranial Doppler signal but also the ease of use. Only if both criteria are fulfilled automated MES detection is likely to be used in clinical practice. Several automated MES detection systems are currently commercially available.
The latest addition is a portable system allowing for recordings of several hours. With the exeption of one system that is installed on an external computer attached to any Doppler machine, all other solutions are build into a given Doppler machine. Few data are available on the reliability of the detection algorithms. All systems are suited for MES within a given dynamic range. In daily practice, very high intensity gaseous bubbles are likely not to be captured, especially not when appearing in clusters. Most systems will produce a list of possible MES - ie. short segments of Doppler signals containing an intensity increase, which have to be checked manually. Especially in patients with an expected low number of MES this approach is reasonable and will result in an enormous saving of time. So, when taking the clinical circumstances and the properties of a given system into account, automated MES detection can be a reasonable adjunct to daily patient care.
Key words: embolus detection, evidence based medicine, transcranial Doppler.