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29. Endovascular Treatment of Carotid and Subclavian Artery Stenosis
Indications for Carotid Stenting
Patients with cerebrovascular disease are at risk for thromboembolic complications from carotid stenosis. Classically, symptomatic or high-grade carotid stenosis has been treated with carotid endarterectomy (CEA). Carotid artery stenting (CAS) also offers stroke risk reduction in patients with symptomatic and asymptomatic carotid disease. It is particularly useful in patients considered high-risk for CEA because of severe cardiopulmonary disease or anatomic reasons such as high lesion location, prior neck surgery, or a history of CEA or irradiation [1].
Approach Considerations for Carotid Stenting
Preoperative Imaging
Cross-sectional imaging is useful to plan the endovascular approach. We prefer CT angiography (CTA) to assess the aortic arch characteristics and the location, dimensions, and characteristics of the carotid lesion.
Type I: The great vessel origins are level with the upper convexity.
Type II: The great vessel origins are between the upper and lower convexity.
Type III: The great vessel origins are caudal to the lower convexity.
Type I and II arches are appropriate for transfemoral stenting. Type III arches present challenges in transfemoral carotid access, so alternatives to this approach should be considered. Similarly, significant aortic arch calcifications, particularly around the ostia of the carotid artery, can result in increased periprocedural stroke risk.
Aortic arch types
When evaluating the carotid lesion itself, it is essential to look for unstable-appearing plaque, embolus, or a high thrombus burden; these are considered contraindications to CAS. Severe carotid lesion calcifications carry a risk of dissection during CAS.
If transfemoral CAS is planned, distal internal carotid artery kinks and loops should be noted, because they preclude the delivery of distal embolic protection devices.
If transcervical CAS is considered, the common carotid artery (CCA) should be evaluated to ensure the absence of anterior calcification at the point of sheath entry and the presence of an adequate length (5 cm) between the clavicle and the carotid lesion to allow for sheath stability. Carotid artery duplex can provide this information if CTA cannot be obtained.
Preoperative Medical Treatment
Patients considered for CAS should be started on statin and dual antiplatelet therapy for at least 5 days preoperatively to reduce the risk of perioperative cerebrovascular accident.
Transfemoral Versus Transcervical Approach
The previously mentioned cross-sectional imaging assists in defining the anatomy to determine whether transfemoral CAS with distal embolic protection or transcervical CAS with flow reversal (transcervical carotid artery revascularization or TCAR) is more favorable. The potential benefits of TCAR are the avoidance of aortic arch and carotid lesion manipulation prior to the initiation of neuroprotection. TCAR is suitable if the patient can undergo a CCA cutdown and sheath delivery proximal to the lesion. The presence of contralateral occlusion is not a contraindication to either technique. It is preferable to avoid transfemoral CAS in patients with type III aortic arch, a diseased arch, or loops or kinks in the internal carotid artery (ICA) distal to the lesion.
Stent Choice and Distal Embolic Protection
Carotid stents currently are produced in several main categories, including closed-cell, open-cell, hybrid, or membrane-covered stents (Fig. 29.2), as well as tapered and straight configurations. Closed-cell designs typically confer greater plaque stabilization characteristics, with potentially fewer or smaller embolic events. Mesh or covered stents are in development and may represent an improved design that may limit embolic events during and after the index stenting procedure. Comparisons between different stent designs have not demonstrated a clinical advantage of one over the others.
Stent types: Closed-cell versus open-cell design
Similarly, no randomized clinical trials have compared the different embolic protection devices (EPDs). Embolic protection devices (Fig. 29.3) have improved rates of stroke and death after carotid artery stenting [2]. There are two main design types, either proximal balloon occluders or distal filters. Distal filters have gained popularity due to ease of use, the ability to maintain cerebral blood flow during the procedure, and their compatibility with other 0.014″ CAS equipment. They do have several disadvantages, including lesion crossing prior to the embolic protection and occasional difficulty in filter retrieval, particularly if it fills with procedural debris. Transfemoral proximal balloon EPDs avoid these issues, but they have not achieved widespread use because they are bulky and relatively more difficult to use, particularly because they require navigation through the aortic arch and balloon placement in the external carotid artery. Transcervical flow reversal avoids arch manipulation altogether, but requires a limited carotid exposure. Early results have revealed fewer periprocedural neurologic events with this technique than had been historically reported with other EPD devices.
Embolic protection devices
Transfemoral Carotid Cannulation and Stenting
Toolkit
Short 5–6 French sheath.
A pigtail catheter.
A range of selection catheters (Fig. 29.4).
A hydrophilic coated wire such as a Glidewire (Terumo; Somerset, NJ) for vessel cannulation.
A stiff wire such as a “carotid” Amplatz Super Stiff Guidewire with a short flexible tip (Boston Scientific; Marlborough, MA) to support proximal carotid sheath delivery.
A long 6 French sheath, such as a 90 cm Flexor Shuttle or Raabe (Cook Medical; Bloomington, IN).
3 mm–5 mm predilation and postdilation 0.014 rapid exchange balloons.
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