Microembolic signals and intraoperative stroke in carotid endarterectomy

Objectives - Microembolic signals (high-intensity transient signals, HITS) detected by means of transcranial Doppler sonography (TCD) may be relevant for intraoperative strokes in carotid endarterectomy (CEA). Material and methods - An intraoperative HITS detection study was performed on 77 patients (63 men, 14 women, mean age±SD, 64±8 years) with a total of 81 CEAs. Using the Scandinavian Stroke Scale the patients were clinically examined by a neurologist preoperatively and postoperatively within 6 h. A deterioration of the Scandinavian Stroke Scale was considered an intraoperative stroke if persisting longer than 24 h. Cranial computed tomography (CT scan) was performed preoperatively and 3 to 5 days postoperatively. By means of TCD total HITS count and mean blood velocity changes, for shunting, were recorded sufficiently in the middle cerebral artery in 79 CEAs. Results - HITS were significantly more frequent in symptomatic [n=53; HITS: median, 15 (range 1-159)] than in asymptomatic stenoses [n=26; HITS: 6.5 (0-41); P<0.001]. An intraoperative stroke in the hemisphere ipsilateral to the operation occurred in eight of the 81 CEAs. On postoperative CT scans, five of the eight strokes showed new corresponding territorial infarctions. In the three strokes without new CT lesions, the mean blood velocity changes after clamping indicated normal cerebral perfusion. Total HITS count was significantly higher in procedures with intraoperative strokes [n=8; HITS: 33 (11-159)] than in the uncomplicated [n=71; HITS: 10 (0-62); P=0.002]. No stroke occurred in 37 CEAs with 10 or less HITS, but eight in 42 CEAs with 11 or more HITS [P=0.006; relative risk 1.23 (95% confidence interval: 1.06 to 1.43)]. Conclusion - Microembolism seems clinically relevant in carotid endarterectomy. Asymptomatic patients may run a lower risk of intraoperative embolization.