Carotid artery stenosis--where do we go from here?

Abstract

Carotid artery stenosis is an important risk factor for stroke. The European Carotid Surgery Trial (ECST) and the North American Symptomatic Carotid Endarterectomy Trial (NASCET) have demonstrated that the risk of stroke is reduced by surgery in patients with high grade stenosis (70-99%). However, because the two trials used different methods to measure stenosis, the results are not comparable and the level of stenosis which is associated with increased risk of stroke cannot be strictly defined. The benefit of surgery in asymptomatic patients is more controversial. Some studies indicate that surgery reduces the risk of stroke only in patients with ?80% stenosis and others have shown benefits for patients with ?60% stenosis. Overall, the benefits of surgery in asymptomatic patients are more difficult to define. Carotid lesion morphology also plays an important role in determining the risk of stroke; plaques which are ulcerated and echolucent are associated with a higher risk of stroke. Arteriography has been long regarded as the gold standard diagnostic tool for carotid stenosis. It is a costly and invasive technique with potentially serious complications. The results of arteriography have not been standardised which makes comparison of results from different laboratories difficult. Duplex ultrasound is inexpensive, non-invasive and can provide functional and anatomical information about vessel stenosis and plaque morphology. The use of echo-enhancing agents helps to reduce operator variability, improves ultrasound images and can help to distinguish between pseudo and true occlusions, to identify patients who will benefit most from surgery. The echo-enhancing agent Levovist(R) is safe, produces consistent results and can enhance images throughout the blood pool. Clinical studies with Levovist(R) have shown it to be safe and highly effective in improving diagnostic confidence in patients with carotid artery stenosis. The number of non-diagnostic scans is reduced markedly when Levovist(R) is used to enhance ultrasound images.