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CHICAGO -- The Asymptomatic Carotid Stenosis: Stenting Versus Endarterectomy Trial (ACT 1) is a prospective, multicenter trial comparing carotid endarterectomy (CEA) and carotid artery stenting (CAS) for the treatment of asymptomatic patients who have significant unilateral carotid stenosis and are at standard risk for both CEA and CAS.

As of late December 2008, 683 of the anticipated 1,858 patients had been randomized, Dr. Jon Matsumura reported at a symposium on vascular surgery sponsored by Northwestern University. Adjudicated data were available on the first 118 patients. Their mean age was 68 years and the average arterial stenosis was 72%. The primary composite end point is 30-day death, stroke, and MI rate, and ipsilateral stroke rate to 1 year post procedure.

The 30-day death, stroke, and MI rate was 1.7% in the 118 patients (all related to two minor strokes). There were no ipsilateral major strokes or deaths. No additional strokes have been reported in 77 patients adjudicated to 1 year, said Dr. Matsumura of the department of surgery at Northwestern University in Chicago.

"This is only a prediction of what the lead-in patients are," he said. "I'm not sure how it's going to apply to the actual randomized patients; the devices are the same, but the investigators are doing their first cases." Patients in the trial, sponsored by Abbott Vascular, are being randomized 3:1 CAS to CEA in an effort to provide a larger sample size of CAS patients to access uncommon CAS issues. Previous trials that directly compared CEA with CAS have generated a wealth of information on CEA, but have included remarkably few asymptomatic patients, he said. For example, CAVATAS (the Carotid and Vertebral Artery Transluminal Angioplasty Study) randomized 504 patients; only 60 (12%) were asymptomatic.

In addition, interventionalists have become more experienced, and CAS technology has matured considerably with the routine use of stenting and embolic protection devices, which were not utilized in CAVATAS, he said. Routine embolic protection and contemporary adjunctive medical therapy are expressly prescribed for all ACT 1 patients.

Dr. Matsumura reported working with companies that make carotid stents.

Two additional trials are in process, that they may help determine the best treatment for asymptomatic patients with carotid stenosis. The United Kingdom's Medical Research Council has funded the multicenter, international ACST-2, a follow-up to the pivotal 1993 ACST (Asymptomatic Carotid Surgery Trial). Patients will be randomized 1:1 to CAS or CEA, and stenting techniques are what the physicians would normally use in their country. Embolic protection is optional.

The German government recently authorized funding for its most expensive trial to date: SPACE-2, which will compare CAS and CEA in asymptomatic patients (roughly 1,550 in each arm), but will also include a third arm with 540 patients treated with conventional medical therapy alone.

Asked to comment, Dr. R. Eugene Zierler of the University of Washington, Seattle, stated: "Previous studies comparing CEA and medical therapy in asymptomatic patients with carotid stenosis have shown that the overall event rate during follow-up is lower than in similar trials of symptomatic patients. It is likely that larger numbers of patients and longer follow-up periods will be required in studies comparing CEA and CAS in asymptomatic patients. While these early data are encouraging, the role of CAS in asymptomatic patients will not be established until long-term follow-up studies are reported."