Historical Background
Balloon angioplasty of the carotid artery was first described in the late 1970s as an intervention for carotid artery stenosis. It was proposed as an alternative to carotid endarterectomy (CEA) in medically high-risk patients and those with hostile neck anatomy. Early trials demonstrated the feasibility of the technique but were not widely accepted because of small study size, high complication rates, and only occasional use of stenting. Carotid angioplasty and stenting (CAS) has evolved to its current form with improvements in equipment and technique, increased operator experience, and standard use of cerebral protection during carotid stent placement.
Indications
Key trials have helped to determine which patients are best treated with CAS, but this issue is not yet resolved. The current indication for CAS is high anatomic or physiologic risk for CEA ( Table 8-1 ).
| Physiologic Criteria | Anatomic Criteria |
|---|---|
| Unstable angina | Lesion above C2 or below the clavicle |
| MI within 30 days | Tandem carotid lesions requiring treatment |
| NYHA class 3 or 4 CHF | Restenosis with prior CEA |
| Multivessel coronary artery disease (nonrevascularizable) | Radical neck dissection |
| Left ventricular ejection fraction < 30% | Tracheostomy |
| Cardiac surgery within 30 days | Cervical radiation |
| COPD (FEV1 < 30% of predicted) | Contralateral carotid occlusion |
| Age > 80 years | Contralateral CEA with cranial nerve injury |
Preoperative Care
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Obtain an understanding of the arch, carotid, and cerebral arterial anatomy before the procedure by arteriogram, computed tomography (CT) angiography, or magnetic resonance angiography. This enhances patient selection and procedural planning.
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A CT or magnetic resonance imaging (MRI) scan of the brain is obtained in symptomatic patients and in those older than 80 years to evaluate for preprocedural cerebral pathology. Patients older than 80 years are at higher risk for stroke after CAS.
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Antiplatelet therapy is initiated with aspirin at 325 mg/day and clopidogrel at 75 mg/day for 5 days before the procedure. In all cases patients should have received clopidogrel (total dose of 300 mg) before the intervention. Patients are asked to discontinue beta-blockers on the day of the stent procedure to help avoid poststent bradycardia.
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A neurologic examination is performed and a stroke scale is completed.
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The procedure is performed under local anesthesia with minimal or no sedation to facilitate patient cooperation and neurologic monitoring. An arterial line is placed for continuous blood pressure monitoring. External pacer pads should be readily available. Patients with severe aortic stenosis undergo placement of a temporary venous pacemaker. Because of the minimal use of sedation, patients may be apprehensive and hypertensive. Avoid acutely reducing the blood pressure during the intervention with pharmacologic agents because poststent hypotension or bradycardia is not uncommon. If antihypertensive medication is required, it is best to use a short-acting agent.
Pitfalls and Danger Points
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Stroke. Stroke may occur with CAS. The perioperative risk of stroke, ipsilateral postprocedural stroke, and death in the Carotid Revascularization Endarterectomy versus Stenting Trial (CREST) was 2.5% for asymptomatic patients and 6.0% for symptomatic patients. Although minor stroke was higher with CAS than with CEA, the incidence of major stroke and death was similar between the two procedures.
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Difficult access of the carotid artery. Tortuous aortic arch or great vessel anatomy must be analyzed and the appropriate steps must be taken to achieve access safely. A reverse-curved catheter may be required for common carotid artery cannulation. A variety of stiff exchange wires may be used to support a carotid access sheath. In some patients with a diseased arch CAS should be avoided.
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Unable to cross the lesion. The curve at the tip of the guidewire may be altered or the crossing wire may be supported with a directional catheter. The patient’s neck position may be changed to make the course into the lesion less angulated. The residual lumen of a complex lesion is most likely to be just posterior to the flow divider. A buddy wire may also be used to facilitate crossing of the lesion.
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Spasm of the distal internal carotid artery (ICA). If ICA spasm is identified during the CAS procedure, small doses of nitroglycerine may be administered into the carotid sheath. Spasm resolves after the filter and wire are removed.
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No flow after stenting. The filter may be full of obstructive debris and should be aspirated before removal.
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Hypotension, bradycardia, or both. Hypotension and bradycardia occur regularly with CAS but are rarely sustained. They are supported with the appropriate pharmacologic agent.
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In-stent restenosis. Recurrent in-stent stenosis appears to occur with a similar frequency after CAS as it does after CEA. It is usually treated with repeat balloon angioplasty and occasionally with repeat stenting. It is rare for carotid stent patients to require arterial replacement.
Endovascular Strategy
Angiographic Anatomy
Study the anatomy of the arch, carotid, and cerebral arteries before the procedure. A view may be obtained by arteriogram, CT angiography, or magnetic resonance angiography and permits patient selection and procedural planning ( Table 8-2 ). Several anatomic factors may be considered relative contraindications to CAS, including severe arch atherosclerosis or tortuosity, diffuse common carotid artery disease or tortuosity, severe angulation of the bifurcation, kinking of the distal ICA, and lack of a filter landing zone in the distal ICA.
| Anatomy or Pathology | Arch | Common Carotid Artery | Bifurcation | Distal ICA |
|---|---|---|---|---|
| Tortuosity | More challenging sheath placement | Potential for less stability of the sheath during the procedure | More challenging lesion crossing | No filter landing zone |
| Calcification | Increased stroke risk with cannulation in the calcified arch | Greater likelihood of embolization with stenting | ||
| Both tortuosity and calcification | Greater likelihood of sheath placement to be a prohibitive risk | More risk of injury to the common carotid artery | Potential inability to deliver the stent | |
| Complex carotid plaque morphology | Echogenic plaque; large plaque burdens are at higher risk for embolization during stent placement | |||
| Thrombus | Free floating thrombus; use proximal protection | |||
| Extra lesions in inconvenient locations | Possible requirement of a separate balloon-expandable stent at the origin of the common carotid artery | Occluded external carotid artery; this branch cannot be used to anchor the exchange guidewire for sheath placement | ||
| Anatomic variants | Identification and management of well-described arch variants | Cerebral collaterals, isolated hemisphere |
Favorable Versus Unfavorable Aortic Arch Anatomy
Arch tortuosity is a significant deterrent to safe and simple access sheath placement. The arch is considered type I if the branches originate at the top of the arch, type II if the arch vessels arise between the parallel planes delineated by the outer and the inner curves of the arch (moderate angulation), and type III if the branches originate along the upslope of the arch, proximal or caudal to the lesser curvature of the arch, or off the ascending aorta (severe angulation; Fig. 8-1 ).
Carotid Lesions at Risk for Embolization
Risky lesions for CAS include those with circumferential calcification, heavy plaque burden, or echolucent plaque and those that are symptomatic, especially if there has been a recent stroke or a series of transient ischemic attacks.
Kinks and Coils of the Carotid Artery
Tortuous carotid arteries can make crossing the lesion challenging, may make the landing zone for the filter too short, or may present a situation in which stenting is not possible because the stent is unable to conform to the tortuous bifurcation and distal ICA. Tortuosity of the artery is not alleviated by stent placement and may be worsened by propagating the tortuosity to another segment of nonstented artery.
Occluded External Carotid Artery
The external carotid artery is used as a location to anchor the exchange wire so that sheath insertion is stable. When the external carotid artery is occluded, or when the carotid bifurcation lesion involves the distal common carotid artery, this is not possible and other maneuvers are required to achieve sheath access, such as telescoping the sheath into the common carotid artery ( Fig. 8-2 ).
Severe Stenosis and String Sign
When there is little residual lumen, there may be slow flow or thrombus accumulation, and flow may stop when the wire is placed across the lesion. With a string sign (severe stenosis with collapse of the distal lumen), sizing of distal filters is difficult because the distal lumen may or may not expand after angioplasty of the bifurcation lesion.
Tandem Lesions in the Common Carotid Artery
Occasionally, a lesion occurs in the proximal common carotid artery (especially at its origin from the arch) and at the bifurcation and both lesions require treatment. Balloon angioplasty of the arch lesion is required to create space for the sheath. The bifurcation lesion is treated with a stent using distal protection in the usual manner, and the common carotid artery origin is stented before fully withdrawing the sheath.
Fibromuscular Dysplasia
The pathology of fibromuscular dysplasia responds well to balloon angioplasty. A stent may be required if the residual surface is highly irregular or mobile. Because the process extends to the base of the skull, there is usually an inadequate landing zone for a filter, and proximal occlusion with reversed flow may be used for cerebral protection. Do not perform angioplasty if the artery is aneurysmal or there is evidence of dissection.
Selection of a Stent: Open- Versus Closed-Cell Designs
Open-cell stents are more flexible and more appropriate for tortuous carotid arteries. Closed-cell stents have smaller cells and better outward radial force. They may result in a lower rate of stroke, but are less conformable.
Cerebral Protection Devices
Currently, the choice for cerebral protection is between filters and occlusion devices (with or without reversed flow). Most stents are placed with filters, but data are developing on proximal occlusion using a variety of techniques. Filter technology continues to improve, but filtration is not complete.
Redo Carotid Angioplasty
Repeat balloon angioplasty is usually adequate to restore the lumen of a restenotic carotid stent, but occasionally an additional stent is required.
Endovascular Technique
Access
The common femoral artery is the access site in most cases, although CAS has also been performed using upper extremity access or direct common carotid artery access. The access site with the simplest and safest path to the bifurcation should be selected. Occasionally, brachial or radial access may be used in the case of a bovine arch or tortuous great vessels. A micropuncture set (21-Ga needle) may be used for the initial access; this has significantly reduced the number of femoral access complications. Following guidewire access, an introducer sheath is placed in the common femoral artery that is the same size as that intended for the carotid stent placement, usually 6 or 7 Fr. When the arch or proximal great vessels are too tortuous or there is significant arch disease, another option is to perform a short transverse neck incision, clamp the common carotid artery, and insert the stent directly through a short sheath. Cerebral protection may be performed using reversed flow or a filter.
Catheterization of the Common Carotid Artery
Catheterization can almost always be accomplished using one of two preshaped catheters: a simple curve catheter such as a vertebral catheter or a complex curve catheter such as the reversed angle Vitek catheter ( Fig. 8-3 ). The image intensifier is maintained in its fixed left anterior oblique (LAO) position, and bony landmarks or a road map may be used to guide vessel cannulation. The catheter of first choice in most cases is a simple curve catheter. The angle formed by the vertebral catheter, along with the tip angle on an angled Glidewire, is adequate to cannulate most common carotid arteries. Once the Glidewire has accessed the common carotid artery, the catheter is advanced over the wire for selective angiograms of the common carotid artery. Do not pass the guidewire into the carotid artery bifurcation without doing an arteriogram. As the cerebral catheter rounds the turn from the arch into the common carotid artery, it tends to straighten out and the guidewire may “jump” forward. This catheter advancement should be visualized under fluoroscopy and carefully controlled. If the catheter catches during advancement, apply only gentle forward pressure so that excessive tension does not build up in the system. Sometimes, having the patient take a deep breath or cough aids catheter passage.
