Prevalence and frequency of microembolic signals in 105 patients with extracranial carotid artery occlusive disease

Besides the established factors "presence of symptoms" and "degree of steno sis", plaque echolucency is considered to be associated with increased risk of stroke in patients with carotid artery disease. An evaluation was carri ed out as to whether the prevalence and number of microembolic signals (MES ) detected by transcranial Doppler ultrasound were higher in patients with echolucent carotid plaques. One hundred and five patients with carotid artery stenosis from 20%-99% or occlusion underwent clinical investigations, duplex ultrasound of the carot id arteries, and a 1 hour recording from the middle cerebral artery downstr eam to the carotid artery pathology using the four gate technique. The pres ence of MES was more frequent and the number greater in symptomatic patient s (21 out of 64 patients (33%); mean number of MES in all 64 patients 3.1) than in asymptomatic patients (four out of 41 patients (10%); mean number o f MES in all 41 patients 0.3) (p=0.007, and p=0.006, respectively). Echogen icity of the lesions did not affect either number or presence of MES. Posit ivity for MES and the number of MES increased with increasing degree of ste nosis (both p=0.002). Four out of 12 patients with carotid artery occlusion showed MES. No MES could be detected in carotid artery stenosis below 80%. There was a decline in positivity of MES and of the number of MES with the time after the ischaemic event. After 80 days or more after the index even t, only one patient showed MES. In conclusion, increasing degree of stenosis and presence of symptoms simil arly affect macroembolic and microembolic risk. Thus MES may be a surrogate parameter for risk of stroke. The presence of MES in a few asymptomatic pa tients suggests that clinically silent circulating microemboli may give add itional information on the pending embolic potential of carotid artery sten oses. Echolucency of the plaque was not related to an increased number of M ES.