抄録
We investigated the characteristics (velocity and frequency) of microembolic signals (MES) detected by transcranial Doppler (TCD) . The subjects were 22 patients (69 ± 9 years old) with cardioembolic stroke (CE), 28 (65 ± 11 years old) with atherothrombotic stroke (stenosis of the internal carotid or middle cerebral arteries) (AS), 36 (63 ± 10 years old) with lacunar stroke (LS), and 9 (57 ± 16 years old) with mechanical valve replacement (MVR) . Using a Multi-Dop X4 (DWL Co., Germany), a 20-min TCD recording was made over the middle cerebral artery. Signals with an intensity of 6 dB or more above the background Doppler spectrum and associated with harmonic sound were defined as MESS. MESs were detected in 23% of patients with CE (17 signals), 71% (144) of patients with AS, 0% (0) of patients with LS, and 100% (88) of patients with MVR. There was a significant positive correlation (p<0.01) between MES velocity and frequency in all types of disease: AS (r=0.84), CE (r=0.80) and MVR (r=0.91) . The ratio of the velocity of MES (M) to that of background blood flow (B) (MB ratio) in AS (0.65 ± 0.21) was significantly smaller (p<0.05) than that in CE (0.77 ± 0.10) or MVR (0.72 ± 0.14) .
These findings suggest that the frequency of the harmonic sound is related to the velocity of microemboli that traverse the ultrasound beam, and that the velocity of microemboli and duration of MESs are inversely correlated. Most microemboli detected in patients with AS flow close to the vascular walls.
