Source of Microembolic Signals in Patients With High-Grade Carotid Stenosis

Abstract

Background and Purpose-In patients with both symptomatic and asymptomatic carotid artery stenoses, the relationship between carotid plaque characteristics and transcranial Doppler (TCD)-detected microembolic signals (MES) is unclear. The purpose of this study was to examine the relationship between macroscopically described plaque characteristics and MES in patients undergoing carotid endarterectomy. Methods-Sequential patients scheduled for carotid endarterectomy underwent preoperative 30-minute TCD monitoring of the ipsilateral middle cerebral artery to detect MES. TCD signal analysis, by researchers who were blinded to patient information, was performed offline. Clinical variables of patients and macroscopic carotid plaque features seen at surgery were documented prospectively. Results-Of the 109 patients (74 male, 35 female; mean age, 68.8Ϯ8.7 years) enrolled, 71 had ipsilateral carotid territory symptoms. MES were detected in 27 of all patients (25%). Twenty-two of 71 symptomatic patients (31%) compared with 5 of 38 asymptomatic patients (13%) had MES (Pϭ0.046). Also, symptomatic patients had more emboli (total MES counts) than asymptomatic patients (Pϭ0.010). The presence or absence of MES was not associated with plaque characteristics. Conclusions-Our data do not confirm previous reports of an association between MES and macroscopic plaque characteristics. We hypothesize that smaller platelet aggregates and fibrin clots, which are not detected macroscopically, are the most likely sources of TCD-detected MES. Key Words: carotid endarterectomy Ⅲ carotid stenosis Ⅲ middle cerebral artery Ⅲ ultrasonography, Doppler, transcranial C arotid stenosis is an important cause of ischemic stroke, with artery-to-artery embolism being the most common mechanism. In 1991, the European Carotid Surgery Trial (ECST) and North American Symptomatic Carotid Endarterectomy Trial (NASCET) investigators reported a beneficial effect in favor of carotid endarterectomy (CEA) in recently symptomatic patients with high-grade carotid artery stenosis. 1,2 The reduction in stroke risk is attributed to removal of the cerebral embolic source in most cases.Asymptomatic cerebral microembolic signals (MES) can be detected in patients with carotid stenosis through the use of transcranial Doppler (TCD). 3,4 Several observations suggest that MES detected distal to a high-grade carotid stenosis are due to unstable plaque. MES are more common among patients with recent carotid artery stroke and are more commonly detected among patients with more severe carotid artery narrowing. [5][6][7][8] Moreover, CEA tends to result in a rapid decline of MES, 9,10 suggesting that their temporal source has been removed.The frequency with which MES can be detected may depend on a number of factors such as duration of monitoring and the interval between symptom onset and TCD study. Reported incidence varies from Ϸ12% 11 to 100%. 9 MES may also be related to carotid plaque morphology. Valton et al 12 showed that MES were associated with carotid plaque ulceration on...

Assessment: Transcranial Doppler ultrasonography: [RETIRED]

“…50 In patients with high-grade carotid stenosis, sources of asymptomatic microembolic signals may include ulcerated plaques 51 and microscopic platelet aggregates and fibrin clots. 52 Asymptomatic cerebral microembolization was associated with an increased risk of further cerebral ischemia (OR ϭ 8.10, 95% CI ϭ 1.58 to 41.57) in this setting. 51 Comparison between studies is difficult because of differences in diagnostic criteria and detection threshold, different instruments, different instrument settings, nature and severity of disease, variability in occurrence of microembolic signals, time between last symptom and detection of microembolic signals, and type of treatment.…”

Correlation Between Carotid Intraplaque Hemorrhage and Clinical Symptoms

“…65,69 In the 2 largest gross inspection studies, old hemosiderin-laden plaques were also considered examples of IPH. 22,23 For macroscopy, IPH was usually characterized by its immediate recognition or on transecting the plaques at the time of arteriotomy.…”

Microemboli Composed of Cholesterol Crystals Disrupt the Blood-Brain Barrier and Reduce Cognition

“…1,2 This incidence increased to 27% with 8 hours of monitoring and to 46% with 16 hours of monitoring. 3 Although these patients' risk of stroke may be low, 4 reduced cognitive function 5 and silent infarctions 6 are more frequent in patients with asymptomatic carotid stenosis compared with controls.…”