Category 10, Item 11
Several recent prospective randomized studies have helped to define the role of carotid endarterectomy for treatment of symptomatic and asymptomatic carotid artery stenosis. Knowledge of the method used to define a carotid artery stenosis is required for proper interpretation of the results. The North American interpretation of an angiographic stenosis defines the percent stenosis as: 100 × (1 – [MRL/DL]), where MRL is the smallest lumen diameter at the site of stenosis and DL is the diameter at the first point distal to the MRL at which the arterial walls become parallel. The Europen method replaces DL with an estimate of the normal carotid diameter at the point of maximal stenosis. This difference in measurement can result in significant differences in diameter stenosis, especially in less severe narrowing. Using the North American method the percent stenosis in this example is: 100 × (1 – [1.1/3.7]) = 70%.
For patients with an asymptomatic carotid artery stenosis greater than 60%, the Asymptomatic Carotid Atherosclerosis Study (ACAS) determined that carotid endarterectomy decreased the risk of ipsilateral stroke from 11% to 5.1% (aggregate risk reduction of 53% [95% confidence interval, 22%–72%]) over five years. This approach was recommended for patients in good general health by surgeons with a less than 3% perioperative morbidity and mortality in conjunction with aggressive management of modifiable risk factors.
If the patient is symptomatic and has a ≥ 70% carotid artery stenosis, the North American Symptomatic Carotid Endarterectomy Trial (NASCET) reported life table estimates of the accumulative risk of any ipsilateral stroke at two years as 26% in the medically treated group and 9% with the addition of carotid endarterectomy. Carotid endarterectomy was highly beneficial for patients with recent hemispheric and/or retinal transient ischemic attacks or nondisabling strokes who had a high-grade stenosis (70% to 99%) of the internal carotid artery. The perioperative risk of stroke or death was 5.8%. Restricting the analysis to major stroke (a functional deficit persisting ≥ 90 days) and death or fatality alone, the risk was 2.1% and 0.6%, respectively.