Timing of clinically significant microembolism after carotid endarterectomy

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.

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.

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).

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.