On the origin of microembolic signals

Clinically silent circulating microembolic signals (MES) can be identified by transcranial Doppler ultrasound (TCD). It is not yet clear whether their occurrence is always linked to the presence of embolic sources. 24 terminally ill patients (7 women, 17 men; mean age 68 years) were investigated by TCD of the middle cerebral arteries. These findings were correlated with a complete post-mortem examination of potential embolic pathways. Four patients out of the 24 under investigation showed MES, 2 of them bilaterally. All these 4 MES-positive patients had a definite embolic source, i. e. bilateral carotid artery occlusive disease, endocarditis with thrombotic valvular adhesions and severe plaques in the aortic arch, dilated left atrium and a patent foramen ovale, or severe plaques in the aortic arch and a dilated left atrium, respectively. In the investigated patient group, we could demonstrate that MES can only be found when an embolic source is present. The finding of MES justifies an extensive clinical and laboratory search for potential embolic sources including extracranial and intracranial colour-coded duplex ultrasound, ECG, Holter-ECG, and TEE.