Doppler Microembolic Signals for Diagnosis of Ulcerated Carotid Artery Plaques

BACKGROUND: Finding the pathological meaning of Doppler microembolic signals is important to developing the clinical applications of this new technology. METHODS: Two hundred eighty-four plaques, removed at carotid endarterectomy, were examined by the surgeon and pathologist for evidence of ulceration. The ipsilateral middle cerebral artery was monitored, with 2-MHz pulsed Doppler, preoperatively and during surgical mobilization of the carotid arteries. Associated Doppler embolic signals representing formed element emboli (FEE) were sought for 15-273 (mean 60) minutes. The embolization rate was calculated in FEE/hour. RESULTS: Preoperatively, 21% of patients demonstrated FEEs. During surgical mobilization of the carotid arteries, 51% demonstrated FEEs. A 79% prevalence of plaque ulceration was found. Analysis demonstrated 61% sensitivity and specificity, and an 86% positive predictive value. The positive predictive value increased progressively with higher FEE rates, up to 100% for patients with >60 FEE/hour. CONCLUSIONS: FEEs detected in the middle cerebral artery ipsilateral to carotid artery stenosis are diagnostic of plaque ulceration or luminal thrombus formation. Other embolic sources may be ruled out by monitoring the contralateral carotid artery system and the ipsilateral carotid arteries. There is no significant relationship between the number and prevalence of FEEs and the severity of stenosis or preoperative symptoms. Postoperative cerebral complications of stroke were associated with more FEEs than were postoperative transient ischemic attacks. (ECHOCARDIOGRAPHY, Volume 13, September 1996)