DETECTION OF TOTAL OCCLUSION, STRING SIGN, AND PREOCCLUSIVE STENOSIS OF THE INTERNAL CAROTID-ARTERY BY COLOR-FLOW DUPLEX SCANNING

BACKGROUND: Stroke prevention depends on the accurate differentiation of surgically treatable preocclusive lesions from total occlusions of the internal carotid artery. This prospective study was undertaken to review the accuracy of color-flow duplex scanning for identifying caro tid string signs, focal preocclusive lesions (95% to 99% stenoses), an d total occlusion of the internal carotid artery. MATERIALS AND METHOD S: Over an 18-month period, 4,362 patients underwent color-flow duplex scanning of the carotid arteries. Angiograms of 596 internal carotid arteries were available for comparison with the duplex scan findings, Total occlusion was diagnosed by the absence of flow in internal carot id arteries visualized on B-mode scanning. Preocclusive lesions were i dentified by a trickle of flow in the vessel lumen. RESULTS: Of 65 col or-flow duplex scans that predicted total occlusion, 64 (98%) were con firmed by angiography. The negative predictive value for total occlusi on was 99%, Twenty-six (87%) of 30 string signs and focal 95% to 99% s tenoses were correctly identified. Color-flow scanning prediction of p reocclusive lesions was accurate in 84% of 31 cases, Low velocities in the internal carotid artery were usually associated with a string sig n, and high velocities with a focal preocclusive lesion. CONCLUSIONS: Color-flow duplex scanning accurately differentiates between stenotic and totally occluded internal carotid arteries. Identification of preo cclusive lesions is not as accurate but the results are promising, Art eriographic confirmation of duplex scan findings is necessary only whe n scans are equivocal.