Background and purpose: The European Carotid Surgery Trial (ECST) and North American Symptomatic Carotid Endarterectomy Trial (NASCET) have shown that endarterectomy reduces the risk of stroke in certain patients with recently symptomatic carotid stenosis. However, they differed in the degree of stenosis above which surgery was reported to be effective. This disparity has led to inconsistent clinical recommendations but may have been due to differences between the trials in the methods of measurement of carotid stenosis and definitions of outcome events.
Methods: To allow direct comparison of analyses from ECST and NASCET, we remeasured the prerandomization ECST carotid angiograms and redefined the outcome events the same way as in NASCET.
Results: We randomized 3018 patients and followed them up for a mean of 73 months. Surgery reduced the 5-year risk of any stroke or surgical death by 5.7% (95% CI, 0 to 11.6) in patients with 50% to 69% stenosis (n=646, P=0.05) and by 21.2% (95% CI, 12.9 to 29.4) in patients with 70% to 99% stenosis without "near occlusion" (n=429, P<0.0001). These benefits were maintained at the 10-year follow-up. However, surgery was of no benefit in patients (n=125) with near occlusion. The effect of surgery in this group was highly significantly different from that in patients with 70% to 99% stenosis without near occlusion (P=0.002). Surgery was harmful in patients with <30% stenosis (n=1321, P=0.007) and of no benefit in patients with 30% to 49% stenosis (n=478, P=0.6).
Conclusions: Results of the ECST and NASCET were consistent when analyzed in the same way. In ECST, surgery was highly beneficial for 70% to 99% stenosis and moderately beneficial for 50% to 69% stenosis. However, contrary to clinical recommendations and current practice, surgery was of little benefit in patients with carotid near occlusion.