Unstable carotid plaques: Preoperative identification and association with intraoperative embolisation detected by transcranial doppler

Abstract

To investigate whether unstable carotid plaque characteristics, as determined by preoperative colour Duplex ultrasonography (CDU) and postoperative histological examination, were associated with particulate embolisation, detected by transcranial Doppler (TCD), during the initial dissection of the carotid bifurcation during carotid endarterectomy(CEA). A prospective, consecutive study was undertaken of 50 patients undergoing carotid endarterectomy(CEA). Leicester Royal Infirmary, Leicester, U.K. Carotid plaques were assessed preoperatively using CDU. Intraoperative TCD monitoring of the ipsilateral middle cerebral artery was performed using a Scimed 2MHz TCD. Carotid plaques removed at operation were processed histologically and multiple sections assessed microscopically. Plaque composition was classified ultrasonically and histologically according to the Gray-Weale classification and plaque surface characteristics were graded according to a five point classification. TCD detected emboli were identified and counted during the initial dissection of the artery. Particulate embolisation occurred in nine patients. Histologically, embolisation was associated with ulcerated plaque in three cases and ulcerated plaque with associated thrombus in six cases (p = 0.0005). However, the ability of CDU to positively predict embolisation based on the correct identification of an unstable plaque surface was only 25%. Embolisation during dissection is strongly associated with ulcerated plaque with associated thrombus. CDU is unable to reliably identify these characteristics preoperatively. Intraoperative TCD monitoring can detect potentially harmful embolisation during this stage enabling surgical technique to be modified appropriately.