Effect of contralateral occlusion on long-term efficacy of endarterectomy in the Asymptomatic Carotid Atherosclerosis Study (ACAS)

Background and Purpose-The Asymptomatic Carotid Atherosclerosis Study (ACAS ) established the effectiveness of prophylactic carotid endarterectomy, for patients in good health who had stenosis greater than or equal to 60%, if conducted by surgeons with a surgical morbidity and mortality of <3%. This secondary analysis was pet-formed to determine whether the presence of cont ralateral cervical carotid occlusion alters the efficacy of asymptomatic ip silateral carotid endarterectomy. Methods-One hundred sixty-three participants who had a baseline contralater al occlusion documented by Doppler ultrasound (77 medical, 86 surgical) wer e compared with 1485 participants with a patent contrarateral carotid arter y (748 medical, 737 surgical) for the risk of a combined end point of perio perative (30-day) death or stroke or long-term (5-year) ipsilateral stroke. Results-For those without contralateral occlusion, surgery was associated w ith a 6.7% absolute reduction in the 5-year risk (95% CI, 2.1% to 11.4%), w hile for those with a contralateral occlusion, surgery was associated with a 2.0% absolute increase in risk (95% CI, -9.3% to 5.2%), which was a stati stically significant difference in the effect of surgery (P=0.047). This di fference is primarily attributable to low long-term risk for medically mana ged patients with contralateral occlusion. Conclusions-While this past hoc analysis should be interpreted with caution , the findings suggest that endarterectomy in asymptomatic subjects with co ntralateral occlusion provides no long-term benefit (and may be harmful) in preventing stroke and death. These findings were a result of the beni,on c ourse of medically treated subjects.