Introduction
The prevalence of asymptomatic carotid artery stenosis (ACS) >50% is about 1%–2% in the general population1,2 (US/European or Korean population) and increases with age ≥70 years up to 12.5% in men and 6.9% in women.3 Choice of treatment for patients with ACS still varies considerably among and within countries4 and is a matter of debate.5,6
Two interventional methods such as carotid endarterectomy (CEA) and
carotid artery stenting (CAS) compete with best medical treatment (BMT)
alone. Guidelines recommending interventional treatment of ACS refer to
data of two large randomized trials (Asymptomatic Carotid
Atherosclerosis Study (ACAS) and Asymptomatic Carotid Surgery Trial 1
(ACST-1)) having compared CEA with conservatively treated control groups
more than 15 years ago. ACAS7 showed in 1995 an annual risk of ipsilateral stroke in medically treated patients of 2.2% and ACST-18 in 2004 a risk of about 1%.
Since then a decline in stroke risk has been shown9,10
and an increasing number of retrospective analyses indicates quite low
annual stroke rates of about 1% or less under modern intensive BMT.11–15
On the other hand, publications with low stroke rates of ACS under BMT
have been criticized for mixing patients with low-grade (50%–69%) and
high-grade (≥70%) stenosis, having small patient numbers, not reporting
adherence to BMT, neglecting transient ischemic attack (TIA)/high-risk
plaque morphology and consecutive carotid revascularization (therefore
preventing stroke), or discriminating insufficiently between ipsilateral
and contralateral events.16
Furthermore, two independent studies showed much higher annual rates of
ipsilateral ischemic events in BMT (2.9% in a group of 1121 patients17 and 2.4% in a group of 794 patients18). However, in ACST-1, lipid-lowering therapy showed lower rates of long-term stroke in both groups,19 indicating that stroke risk decreases with intensive medical therapy including statin medication9 by plaque stabilization and consecutive reduction of microembolization.20–23
To
establish any benefit of interventional therapies over BMT alone,
peri-interventional complications such as stroke, myocardial infarction,
and death have to be taken into account. The peri-interventional risk
of stroke within the first 30 days in the asymptomatic cohort of the
Carotid Revascularization Endarterectomy Versus Stenting Trial (CREST)
was reported with 1.4% for CEA and 2.5% for CAS.24,25 In the Asymptomatic Carotid Trial (ACT-I), it was 1.4% for CEA and 2.8% for CAS.26 Data collected outside randomized controlled trials indicate even higher stroke rates27,28
Regarding composite endpoints including stroke, death, and myocardial
infarction, the peri-interventional risk for patients with ACS partially
exceeded 3%: Within the first 30 days from intervention, it amounted to
3.6% for CEA and 3.5% in CAS in CREST24,25 and to 2.6% for CEA and to 3.3% for CAS in ACT-I.26
Considering the low risk rate under modern pharmacotherapy,
interventional therapies have to prove at least non-inferiority to BMT
alone.29
In
order to attain a higher evidence level for treatment of ACS based upon
optimal current treatment options, randomized controlled trials
comparing CEA with CAS with a third medical arm were requested.30–33
Up to now, no data of randomized controlled trials with a BMT arm have
been published. The SPACE-2 trial was initiated in 2009 comparing both
interventional methods to BMT alone. Due to low recruitment rates,
further enrollment had to be stopped prematurely.34 Data from the one-year follow-up examination are presented in this publication.
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