Interventional Neuroradiology
Carotid Angioplasty and Stenting
From: Neurovascular Newsletter June 1998
Ronald Budzik, M. D.
Christopher M. Putman, M. D.
Alexander Norbash, MD
Stroke is the third leading cause of death in the United States, and represents a
major cause of morbidity in the adult population. Although there are many causes
of acute stroke including emboli from the heart, blood vessel dissection, and
small perforator vessel occlusion, a common treatable cause of acute stroke is
atheromatous narrowing at the carotid bifurcation. It is generally believed that in
this situation ischemic stroke most commonly occurs from local thrombus
formation that develops as a consequence of both ulceration and laminar flow
disturbances in and around the stenotic lesion. This local thrombus formation
serves as a source for eventual arterial to arterial thrombo-embolism into the
intracranial circulation, most commonly to the middle cerebral artery territory.
Less frequently, ischemic stroke may be due to low flow from a critical stenosis
resulting in a hemodynamic insufficiency to a region of the brain.
Carotid endarterectomy is currently the treatment of choice for atheromatous
carotid artery stenosis at the bifurcation. Recent large series demonstrate a
benefit of surgical therapy for symptomatic carotid stenoses of greater than 70%
lumenal narrowing, and for asymptomatic stenoses greater than 60% compared
with conservative medical management. This conclusion is based on large
studies in which the procedural complication rates are weighed against the
reduction in stroke rates from the intervention. According to actuarial analysis, by
two years the risk of ipsilateral stroke was 9% for surgical patients and 26% for
medically treated patients, a 17% reduction in absolute risk with surgery
(reference 1). Because stroke rates on medical management are low, the
periprocedural complication rate (stroke rate) must be minimized in order to
obtain a benefit for patients. However, the risk of perioperative stroke or death is
highly dependent on the experience and technical expertise of those performing
the procedures and is highly variable. The North American Symptomatic Carotid
Endarterectomy Trial reported 0.6% mortality, 5.5% perioperative
cerebrovascular events, and 2.1% major stroke (reference 1). A more recent
review of the published literature reported a 5.6% risk of perioperative stroke
and/or death (reference 2). However, complication rates as high as 18-19% have
been reported. Patients with higher risk of procedural complications from carotid
endarterectomy often have confounding medical problems, such as coexistent
angina, vascular anomalies (high carotid bifurcation), prior radiation treatment or
are undergoing repeat surgery for restenosis. In an effort to reduce the treatment
complications in these patients, new innovative treatments such as angioplasty
and stenting are being developed.
In the past several years, multiple centers in the United States and abroad have
begun evaluating balloon angioplasty and vascular stenting as an alternative to
surgical carotid endarterectomy for carotid stenosis in high risk patients. The
procedure is relatively straightforward, simple, and minimally invasive. The use of
metallic vascular stents for the carotid arteries, similar to those that have been
used to treat stenoses in the coronary, renal, and iliac arteries, has become
widespread. Balloon angioplasty alone, by design, causes a controlled dissection
of the vessel wall, widening the vessel lumen. Stenting following or during
angioplasty is thought to assist in covering the region of dissection induced with
angioplasty, potentially reducing the risk of procedure related thrombo-embolism
to the brain. The use of a stent is also thought to reduce the risk of acute
restenosis seen following angioplasty in other vascular systems, which could be
disastrous in the carotid system. Long term restenosis is a problem with
endarterectomy as well as with angioplasty alone. The use of stents in
conjunction with angioplasty for the carotid system may also reduce the long
term risk of restenosis as has been show in other vascular systems.
After a patient has been referred for treatment and has had an appropriate
neurological and vascular work up suggesting that treatment may be indicated,
diagnostic angiography and potential angioplasty and stenting can be performed.
In most cases the procedure can be performed via a standard percutaneous
transfemoral approach with the patient anesthetized using light intravenous
sedation. Standard diagnostic carotid and cerebral angiography is first performed
to confirm the suspected lesion and to evaluate the cerebral circulation for
collaterals. Prior to treating the stenosis the patient is anticoagulated and an
antiplatelet agent given. To treat a typical stenosis in the proximal internal carotid
artery, a guiding catheter is placed from the groin into the common carotid artery.
A microwire is used through the guiding catheter to gently cross the stenotic
lesion in the internal carotid artery. If the stenosis is too tight to pass a stent
primarily, an angioplasty balloon is passed over the microwire to predilate the
stenosis in preparation for stent placement. Leaving the microwire across the
dilated segment, the balloon is removed and exchanged for the stent delivery
device. Once in position, the stent is deployed across the region of the stenosis.
If needed, an additional balloon can be placed inside the deployed stent for postdilation to make sure the struts of the stent are pressed firmly against the inner
surface of the vessel wall. (Apposition)*
Angioplasty and stenting of carotid stenosis has several potential advantages
when compared with surgical endarterectomy. Since no surgical incision needs
be to be made in the neck, scarring of the neck related to previous surgery,
radiation or trauma do not interfere with the ability to safely reach the lesion for
treatment. Also, stenoses that are out of the reach of the usual surgical exposure
such as high carotid bifurcations (above the mandible) or those at the skull base
do not pose any additional technical challenges. Less importantly, no scar in the
neck is made and local complications from surgery such as infection, cranial
nerve deficits, and hematomas are for the most part not seen with angioplasty
and stenting. Finally, re-treatment of restenosis is a technically simple procedure
with angioglasty and stenting compared with a technically challenging procedure
with re-do endarterectomy. Angioplasty and stenting does not have an advantage
compared to carotid endarterectomy in several important areas. A local
anesthesic can be used for either procedure CEA or angioplasty and stenting in
most patients. Expense, length of hospital stay and recovery times are similar for
both procedures. As of yet, angioplasty and stenting cannot claim equal safety
compared with CEA and no studies have addressed long term outcomes of
patients following stenting.
Published data evaluating the use of carotid angioplasty and stenting is
somewhat sparse compared to the relatively widespread use of the new
technique. Initial results are encouraging, but complication rates are difficult to
define as with any new procedure. Patients with multiple medical problems or
with difficult lesions were often the majority of patients included in the published
series making direct comparison with the results of endarterectomy difficult. Initial
reports suggest complication rates for minor stroke, major stroke, and death in
the 2-10% range (reference 3). Most patients treated with the new technique
have been symptomatic; many have had other medical problems which were
thought to elevate the risks of endarterectomy. However, some centers are
treating asymptomatic patients with high grade stenosis of the internal carotid
artery.
We have performed carotid angioplasty and stenting in selected cases of
symptomatic lesions, and believe patients should be selected carefully for
treatment with this new procedure. We reserve the use of the procedure for
patients who would otherwise benefit from carotid endarterectomy but have
features of their condition which place them at a high surgical risk. These include:
1) re-operation for progressive stenosis following one or more CEAs, 2)
excessive scarring following previous surgery, or radiation (i.e. following
treatment of head and neck cancer), 3) high carotid bifurcations, 4) tandem
stenotic lesion of the carotid, 5) intra-petrous carotid stenosis. Close pre and post
treatment evaluation should be performed, if possible by a neurologist
specializing in cerebrovascular disease and stroke. Patients should be treated in
a center with expertise in managing the complications related to the procedure
such as cerebral emboli.
References:
1. North American Symptomatic Carotid Endarterectomy Trial Collaboration.
Beneficial effect of carotid endarterectomy in symptomatic patients with high
grade carotid stenosis. N Engl J Med. 1991;325:445-453.
2. Rothwell PW, Slattery J, Warlow CP. A systematic review of the risks of stroke
and deathe due to endarterectomy for symptomatic carotid stenosis. Stroke.
1996;27:260-265.
3. Balousek PA, Smith WS, Gress DR, Halbach VV, et al. Angioplasty and
stenting for carotid occlusive disease: Current status and recommendations.
Journal of Neurovascular Disease 1997;2(2):52-58.
4. Bettman MA, Katzen BT, Whisnant J, et al. 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. Circulation
1998;97:121-123.
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