Microembolic Signals in Patients with Acute Nonembolic Stroke

Abstract

The nature of microembolic signals (MES) in patients without apparent sources of embolism remains elusive. We hypothesize that MES in acute stroke patients without an embolic source may represent a transient phenomenon related to blood rheology or clot dissolving, in which case the characteristics of such MES would differ from those with definitive sources of emboli. We compared the intensity and duration of 250 MES in 62 acute nonembolic stroke patients (stroke group) and 217 MES in 57 patients with asymptomatic carotid stenosis (≥50%; carotid group). The duration of MES was significantly different between the 2 groups (24.86 ± 0.89 ms in the carotid group v 18.8 ± 0.83 in the stroke group; P < .001). When comparing the groups for MES with an intensity higher than 6 dB, a highly significant difference in the duration of MES was found (27.87 ± 1.26 ms in the carotid group v 18.57 ± 1.29 ms in the stroke group; P < .0001). A strong linear relationship between the duration and intensity of MES was found for the carotid group, but not for the stroke group. There are significant differences between the characteristics of MES in acute stroke patients as compared with MES in patients with carotid plaques. There is a strong correlation between the intensity and duration of MES from a definitive embolic source, which is absent from MES in patients with nonembolic stroke. These findings may point to the different mechanisms of MES origin in the examined groups.