Timing of Clinically Significant Microembolism after Carotid Endarterectomy

Abstract

Purpose: Post-operatively detected transcranial Doppler (TCD) embolic signals (ES) are associated with an increased risk of carotid endarterectomy (CEA) stroke/TIA. The aims here were to quantify this risk and determine the most efficient monitoring protocol. Methods: Sequential patients undergoing CEA (enrolled in a randomised, blinded, placebo-controlled trial of peri-operative dextran therapy) had 30-min TCD monitoring in the first post-operative hour. 30-min monitoring was also performed 2–3, 4–6 and 24–36 h post-operatively. First post-operative hour ES counts were correlated with peri-operative ipsilateral carotid stroke/TIA to determine the size of a clinically significant ES load and the magnitude of the associated risk. The exact Cochran-Armitage test for trend in proportions was used to determine when a clinically significant ES load was first detected. Results: 141 patients (mean age 69.3 years, 72% male) were monitored during the first post-operative hour. An ES count >10 per recording was identified as the best overall predictor of ipsilateral stroke/TIA (sensitivity 72%, specificity 89%). 3/119 (2.5%) patients with 0–10 ES had ipsilateral carotid events compared to 8/22 (36.4%) patients with 11–115 ES (OR = 22.1, 95% CI 4.5, 138.4, p < 0.0001). 13/18 (72%) of subjects with >10 ES were identified in the first post-operative hour with no significant increase in the number of new cases over the subsequent 24–36 post-operative h (p = 0.354). Conclusion: Patients with clinically significant post-operative microembolism had an approximately 15 times higher risk of ipsilateral stroke/TIA and most were identified during a 30-min study in the first post-operative hour.

Transcranial Doppler Ultrasound Detection of Microemboli as a Predictor of Cerebral Events in Patients with Symptomatic and Asymptomatic Carotid Disease: A Systematic Review and Meta-Analysis

“…Eight studies, with a total of 1414 individual patients, reported stroke or TIA as an outcome along with data for TCD recording of microembolic signals with high MES counts defined as positive (13,(17)(18)(19)21,32,33,35). The sensitivity and specificity were 52.…”

Intraoperative Microemboli and Low Middle Cerebral Artery Blood Flow Velocity Are Additive in Predicting Development of Cerebral Ischemic Events After Carotid Endarterectomy

“…1 These deficits may also occur secondary to postoperative generation of emboli from the surgical site. 2 Intraoperative assessment of the middle cerebral artery (MCA) with transcranial Doppler (TCD) allows online surveillance of hemodynamic changes and can detect passage of cerebral microemboli. 1 Microembolic signals (MES) on intraoperative TCD monitoring are detected in more than 90% of patients undergoing CEA.…”

“…3,5 Although the highest number of MES occurs during declamping of the ICA, detection of MES during dissection of the carotid arteries or during the first postoperative hour correlates with the development of new ischemic lesions on postoperative diffusion-weighted MRI (DWI) or new neurological deficits immediately after CEA. 2,3,5 The target vessel is not opened during dissection, and, thus, all detectable MES are solid. 3 Furthermore, during this stage of the procedure, the fragile plaque, a source of emboli, has not yet been removed and is still exposed to blood flow.…”

“…Detectable MES during the early postoperative period may also be solid (eg, thromboemboli). 2 In addition, an MES count Ͼ10 during these phases is a predictor of the development of new neurological deficits. 2 By contrast, a high number of harmless gaseous MES may develop during carotid declamping.…”

“…2 In addition, an MES count Ͼ10 during these phases is a predictor of the development of new neurological deficits. 2 By contrast, a high number of harmless gaseous MES may develop during carotid declamping. 3,5 Caplan and Hennerici previously reported that hemodynamic and embolic mechanisms are strictly linked and may interact to determine the ultimate degree of cerebral ischemia.…”