Asymptomatic Carotid Surgery Trial
(ACST)
Trial Background
The
current incidence of stroke in Europe and the USA is about 200 per 100,000
population per annum1,2. Eighty percent of strokes are ischaemic
and 20% are due to haemorrhage. Approximately half the patients with ischaemic
stroke have carotid artery stenosis3 and about one third (~10%
all stroke victims) have had no warning symptoms such as transient ischaemic
attacks4.
The European Carotid Surgery Trial (ECST)5 and the North American Symptomatic Carotid Endarterectomy Trial (NASCET)6 have effectively shown that carotid endarterectomy (CEA) can prevent strokes in symptomatic patients. The benifit of surgery is, at present, confirmed in those with at least 70% stenosis; for 50-60%, the results are somewhat equivocal7.
In asymptomatic patients the Veterans Administration Study8 and the Asymptomatic Carotid Atherosclerosis Study (ACAS)9 suggested that surgery may reduce the overall risk of TIA and stroke. There is as yet no convincing evidence in asymptomatic patients that moderate or severe stroke (or death) can be prevented by CEA.
The Asymptomatic Carotid Surgery Trial (ACST) aims to determine whether CEA and appropriate best medical treatment (BMT) can improve stroke free survival time when compared to BMT alone. Furthermore, it aims to identify subgroups of patients who would benefit most from or should not have surgery. Eligible patients should have had no symptoms directly related to the carotid stenosis in question within the previous 6 months.
The ACST is a multi-centre, international, MRC funded trial. Recruitment of patients began in 1993, and 3043 patients have been entered so far. With a target recruitment of 3200 patients, the ACST is due to become one of the world’s definitive carotid surgery trials.