Colour-coded duplex sonography of preocclusive carotid stenoses.

OBJECTIVE: The accuracy of colour-coded duplex sonography (CCDS) for differentiating preocclusive stenoses from occlusions of the internal carotid artery (ICA) is a crucial point in non-invasive quantification of atherosclerotic lesions prior to carotid endarterectomy. METHODS: A total of 401 consecutive patients with CCDS followed by ICA arteriographies as gold standard was available for comparison. The entire number was divided into groups of <90%, 90-94%, preocclusive (95-99%) stenoses and occlusions. Sensitivity, specificity, and predictive value for distinguishing these groups were calculated using a contingency table. RESULTS: With CCDS we found a sensitivity of 88% and a specificity of 99% in 43 preocclusive ?95% stenoses. Similar findings were seen in 31 occlusions of the ICA (SE 87%, SP 99%). CCDS accurately differentiates the subgroups of severe carotid obstructions (90-94%, ?95% and occluded) shown by a predictive accuracy of 97, 96 and 93%. Carotid endarterectomies were performed in two of three angiographically occluded but sonographically preocclusive arteries. Intraoperatively preocclusive ICAs were seen in both cases. CONCLUSION: CCDS showed a high accuracy for differentiating preocclusive stenoses and occlusion of the ICA. Intraoperative findings indicated that angiography is not the absolute gold standard for preocclusive carotid disease in every case. Irregularities of the stenosis channel make it impossible to estimate the true area reduction in stenoses ?90%. The hemodynamic estimation of degree of stenosis by Doppler ultrasound may be closer to reality than angiographic measurement.

[Color-coded duplex ultrasound in pre-occlusive stenoses of the internal carotid artery]. / Farbkodierte Duplexsonographie bei präokklusiven Stenosen der Arteria carotis interna.

In a prospective study the results of 238 consecutive ultrasound examinations of the carotid artery were correlated with angiography to test the reliability of colour coded duplex sonography in preocclusive carotid artery disease. This series was compared with a series of 611 vessels with angiographically controlled conventional duplex sonography. In 61 resp. 84 cases stenoses > or = 90% or occlusions of the internal carotid artery were found. The reliability of colour coded duplex sonography for the diagnosis of > or = 90% stenoses was extremely high (sensitivity and specificity 98%), as well as in preocclusive, > 95% stenoses (100% and 98%), and for the diagnosis of occlusion, after exclusion of angiographic false positive diagnosis of occlusion (95% and 99%). Statistically colour coded flow imaging failed to increase significantly the high diagnostic sensitivity or specificity of conventional duplex sonography, especially in preocclusive carotid artery disease. However, the remarkable increase in frequency of the diagnosis preocclusive stenosis with the introduction of colour coded Duplex Sonography probably reflects a higher sensitivity of this method. In addition the direct comparison of both ultrasound techniques showed a better image of the vessel wall abnormalities and the residual lumen with colour coded duplex sonography.