Carotid endarterectomy for asymptomatic carotid stenosis.

We announce the completion of acquisition of patients for a prospective randomized clinical trial designed to determine the role of carotid endarterectomy in the treatment of patients with asymptomatic carotid stenosis. We also respond to a previous editorial concerning this trial. This on-going multicenter trial (Cooperative Studies Protocol #167, Asymptomatic Carotid Stenosis: Etiological Importance in Development of Stroke) has been conducted in 10 Veterans Administration Medical Centers during the last 5 years. Randomization of 451 adult male patients with a mean age of 64 years to treatment with carotid endarterectomy plus aspirin versus treatment with aspirin alone was completed in November 1987. Mean clinical followup is currently 36 months, and a 60-month followup is planned before the outcome results are reported. Compared with other studies on carotid bruit,this trial included only patients with hemodynamically significant stenoses defined as luminal reductions on lateral arteriography of ^50%, a luminal area reduction of ^75% in the presence of positive noninvasive testing. Contrary to Dyken's editorial opinion, these lesions are associated with an increased rate of transient ischemic attack (TIA) and stroke. Chambers and Norris reported an 18% annual rate of TIA and stroke in an asymptomatic population with area reductions of s75% compared with a rate of <3% in patients with lesser stenoses. Furthermore, significantly higher annual neurologic event rates were observed in patients with progressing carotid artery stenoses and heart disease and in male patients. Consequently, the concept of identifying asymptomatic patients with high-grade stenoses or noninvasive evidence of increasingly severe stenoses as a stroke-prone group is valid and forms the basis for this trial. The magnitude of operative stroke and death is of paramount importance in the decision for carotid