The International Cooperative Study of Extracranial/Intracranial Arterial Anastomosis (EC/IC Bypass Study): methodology and entry characteristics. The EC/IC Bypass Study group.

Abstract

This report summarizes the protocol of a randomized trial of superficial temporal artery-middle cerebral artery (STA-MCA) bypass procedure and presents the entry characteristics of its patients. The trial has been designed to determine whether this EC/IC bypass reduces the rate of subsequent stroke among patients with recent hemispheric or retinal strokes and/or transient ischemic attacks who have angiographically proven atherosclerotic narrowing or occlusion of the ipsilateral internal carotid or middle cerebral artery. Of the 1377 eligible patients entered from the 71 participating centers, 714 (52%) have been assigned to medical treatment alone (daily aspirin and aggressive hypertension control) while 663 (48%) have been assigned to receive STA-MCA bypass in addition to medical therapy. The two treatment groups have been well balanced for important prognostic factors. Bypass patency rates of 95% have been documented. At the end of the study in mid-1985, an average follow-up of five years and a minimum follow-up of 33 months will have been achieved. On both clinical and methodologic grounds, this study will have provided a rigorous test of the STA-MCA bypass procedure.