Composition of particles associated with embolic signals on transcranial doppler untrasonography.

The composition of particulate emboli associated with detectable signals on transcranial Doppler (TCD) ultrasonography has previously been studied in vitro. The purpose of this investigation was to study the composition of particles associated with similar signals in patients undergoing carotid endarterectomy. We studied carotid endarterectomy specimens from four consecutive patients with internal carotid artery origin, symptomatic, severe, stenosis, and preoperative TCD showing signals that were unidirectional from the baseline, occurred throughout the cardiac cycle, lasted 25-100 ms, had intensities exceeding that of surrounding blood by at least 12 dB, and were associated with a characteristic chirping sound. In all patients, signals with the preceding characteristics were detected in the sup-raclinoid internal carotid artery distal to the symptomatic, cervical stenosis. In Cases 1, 3, and 4, no signals were detected in the contralateral, asymptomatic supraclinoid internal carotid artery, and signals resolved after surgery. Examination of the endarterectomy specimens showed intraluminal thrombi composed of fibrin and platelets in all cases. Our findings suggest that TCD signals with the preceding characteristics may correspond to platelet and fibrin particles originating at stenotic lesions of the cervical internal carotid artery.