Although mortality associated with conventional antiplatelet
therapy has been minimal,7 surgery clearly has significant
perioperative morbidity and mortality. This risk varies
as a function of the skill and experience of the surgeon and ancillary
personnel. In one large study of symptomatic
patients,3 surgical complication rates were 0.6%
mortality; 5.5% perioperative cerebrovascular events;
and 2.1% major stroke. By contrast, over the same 32-day observation
period, patients treated medically had a 0.3% fatality rate, a 3.3%
risk of a cerebrovascular event, and a 0.9% risk of a major event. In
a recent review of the published literature, risk of stroke and/or
death following carotid endarterectomy in
symptomatic patients was found to be 5.6%, although there
was substantial variation in incidence as a function of the type of
study and the nature of postoperative evaluation and
surveillance.8 Surgery, then, in this
symptomatic group of patients with significant carotid
artery stenosis has a low but significant incidence of
periprocedural complications. More importantly, however, according to
actuarial analysis, by 2 years the risk of an ipsilateral
stroke was 9% for surgical patients and 26% for medically treated
patients, a 17% reduction in absolute risk with
surgery.3
Since its development by Gruentzig9 in the early 1970s,
use of balloon angioplasty for treatment of atherosclerotic and other
vascular stenoses has gained wide acceptance. In many
trials involving many organ systems, percutaneous
transluminal angioplasty (PTA) has been shown to be effective. Despite
several large studies, however, there is still debate about its
relative efficacy and applicability compared with surgery, primarily
because long-term patency after PTA is limited by restenosis as
well documented in coronary, renal, and peripheral
applications.10 11 12
Vascular stents have gained wide popularity over the last several
years. There are many types with different characteristics, in
different stages of clinical use and FDA approval. More than a dozen
companies are actively marketing or investigating stents in the United
States. In almost all studies directly comparing PTA and stents, the
patency rate with stenting has been at least slightly higher compared
with angioplasty alone.13 14 A direct comparison of
primary stent placement and surgery in any vascular system, however,
has not been completed.
Over the last 2 to 3 years there has been a great deal of
interest in treating extracranial carotid stenoses with either
angioplasty or stents. Extracranial carotid PTA has been in use for
nearly a decade, although no large studies have been reported. Several
reports of carotid angioplasty and stenting have been published or
presented at recent medical meetings, including the annual
scientific sessions of the AHA.15 16 17 The relative
technical ease of performing carotid angioplasty or stenting has
attracted considerable attention in the clinical community. A
randomized multicenter clinical trial sponsored by the Medical Research
Council is in progress in the United Kingdom,18 and one or
more are under consideration in the United States. The potential for
both relative technical ease of performing carotid PTA and stenting and
the low cost of these procedures, although perhaps illusory, are
appealing and justify consideration of a percutaneous
approach as an alternative to carotid
endarterectomy. Before widespread clinical use can
be proposed, however, several important points must be considered.
First, the benefit of carotid endarterectomy in
symptomatic patients has been convincingly demonstrated in
well-controlled prospective randomized trials. The complication rates
have been well defined and, although varied in the literature, appear
to be acceptably low in the hands of experienced surgeons.
Second, although carotid angioplasty and stenting are less
invasive than surgery, the risks of diagnostic carotid
angiography alone with its attendant catheter manipulation are not
trivial. In some reports the risks approach those of carotid
endarterectomy. Before carotid PTA and stenting can
be considered for wide use, morbidity and mortality rates must be
clearly and definitively elucidated, and training criteria must be
established.
Third, unlike with coronary or iliac angioplasty, acute
occlusion of the carotid artery may not be amenable to emergency
surgical correction. Furthermore, if restenosis occurs after
stenting, the standard surgical therapy may be either impossible or
substantially more difficult to perform because of the stent. This is
not true for percutaneous interventions in other
vascular systems. Neither of these concerns has been borne out in
experience to date, but more data are clearly necessary to address
these potential problems.
Fourth, carotid endarterectomy is relatively safe
and inexpensive with a generally brief associated hospitalization. It
is now frequently performed, using regional or local
anesthesia, with good results. This is not true for other
surgical alternatives to stenting, such as coronary bypass
surgery or aortobifemoral or femoral-popliteal grafting. Success rates,
complication rates, and hospital length of stay are all favorable when
carotid endarterectomy is performed by experienced
surgeons, even in patients considered to be at very high risk for other
interventions. As a minimum, the equivalence of
percutaneous approaches to surgical carotid
endarterectomy must therefore be established in
sufficiently powered, prospective randomized trials.
The question that must be addressed, then, is whether carotid
angioplasty or carotid stenting should be performed at all and, if so,
by whom: persons with extensive experience in other vascular systems or
persons trained in neurovascular percutaneous
procedures? Unlike many areas of medicine in which clear answers are
elusive, in this case an answer emerges. At this point, carotid
angioplasty and carotid stenting, with rare and infrequent exceptions,
should be undertaken only as part of a prospective, randomized trial
with independent, dispassionate oversight. In addition to the British
study already under way and the proposed large-scale US studies of
carotid stenting versus endarterectomy, other
trials may be justifiable, but certain requirements must be met. First,
symptoms and signs of cerebrovascular disease in eligible patients
should be well delineated, and enrollment of all such patients should
be attempted. Second, such trials should allow for standardized
training of participants to overcome the problems of a learning curve
as much as possible. Third, sufficient numbers of patients must be
enrolled and followed for a sufficient period of time, a minimum of 2
years, to allow relevant comparisons to be made with adequate
statistical power. To show equivalency of the two treatments, assuming
that there is a major event rate of 5% with surgery and that event
rates differ by 2% or less, at least 3000 patients would be
necessary.
Obviously there are difficulties with such randomized studies. Perhaps
most glaringly, carotid angioplasty and stenting are already being used
and reported by a number of institutions. In addition, stent technology
is evolving, and the best currently available stents may be rapidly
supplanted. Any study must allow for inclusion of significant
technological advances. In this regard, collaboration with industry and
the Food and Drug Administration is imperative; at least two small
industry-sponsored studies are under way. Additionally, to ensure that
such studies are not unduly biased by lack of experience, in certain
situations a supervised, carefully defined registry may be advisable.
This approach would require establishment of a team (including a
neurologist, interventional radiologist, vascular surgeon,
interventional cardiologist, and neurosurgeon) that, under careful
institutional surveillance, could develop experience and a track
record.
The techniques of carotid angioplasty and carotid stenting are
available, as are a limited degree of experience and a high level of
interest. The existence of a technique, however, does not justify or
mandate its use. We must remember a basic tenet of medicine:
primum non nocere—first do no harm. At this point, with few
exceptions, use of carotid stenting should be limited to well-designed,
well-controlled randomized studies with careful, dispassionate
oversight. This will allow accurate comparison of a promising tool with
the well-described, relatively safe gold standard of surgical carotid
endarterectomy. Use of the technology because it
and the patient it is to benefit exist is not at this point justified
or justifiable.
This statement also appears in the Journal of Vascular and Interventional Radiology (January 1998) and Circulation (January 6/13, 1998).
A single reprint is available after January 30, 1998, by calling 800-242-8721 (US only) or writing the American Heart Association, Public Information, 7272 Greenville Avenue, Dallas, TX 75231-4596. Ask for reprint No. 71-0134.
© 1998 American Heart Association, Inc.
AHA Science Advisory
Carotid Stenting and Angioplasty
A Statement for Healthcare Professionals From the Councils on Cardiovascular Radiology, Stroke, Cardio-Thoracic and Vascular Surgery, Epidemiology and Prevention, and Clinical Cardiology, American Heart Association
Key Words: AHA Medical/Scientific Statement • stents • angioplasty • stroke • surgery
Introduction
Top
Introduction
References
Carotid artery stenosis, particularly involving
the origin of the internal carotid artery, is a frequent clinical
problem. These stenoses, almost invariably atherosclerotic, can
present as asymptomatic bruits discovered on physical
examination, one or more transient ischemic attacks related to
embolization of thrombus from stenotic lesions or to
hypoperfusion, or less commonly, as an ischemic stroke. From
the results of three high-quality prospective randomized
trials,1 2 3 it has become apparent that
symptomatic stenoses that narrow the diameter of
the carotid artery more than 60% to 70% lead to a significant
incidence of stroke if treated medically. The risk of stroke associated
with such a lesion in symptomatic patients treated with
antiplatelet therapy alone is thought to be 26%.3
With carotid endarterectomy and aspirin, this risk
is lowered to 9%, a statistically significant
difference.3 In patients with or without symptoms who have
a stenosis 
60%, the effectiveness of either medical therapy
or carotid endarterectomy in preventing significant
neurological events is not known. In symptomatic patients
with <30% stenosis, medical therapy is superior to surgical
therapy.2 Studies attempting to define the benefit of
therapy in symptomatic patients with <60%
stenosis are currently under way. Accrual of patients has
slowed, however, because data show clear efficacy in
symptomatic patients with stenoses 
70%, leading
to a bias toward surgery in symptomatic patients with less
severe stenoses. In general the role of surgery for
asymptomatic stenosis remains controversial, with
some recent opinions suggesting that it may not be
indicated.4 In one high-quality trial with selected
experienced surgeons, there was a modest reduction in absolute risk in
asymptomatic patients with stenosis 60%, but the
significance of this finding has been debated.5 6
Footnotes
"Carotid Stenting and Angioplasty" was approved by the American Heart Association Science Advisory and Coordinating Committee in September 1997.
References
Top
Introduction
References
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