Complications Associated With Carotid Artery Stenting

Introduction

Interventionalists are especially cautious with carotid artery stenting (CAS) because complications can lead to devastating and permanent neurological sequelae, even death. Preparation for CAS can often seem excessive; however, careful and detailed planning is the key to circumvent unwanted outcomes. CAS should be used for appropriately selected patients. Knowing the fundamentals of the procedure and some tricks to adapt the procedure for the patient’s anatomy and disease are important to avoid complications.

Ironically, some of the initial studies evaluating CAS were performed using stenting to treat intimal flap complications sustained during carotid angioplasty for stenosis. At the time, the bailout seemed an appropriate option given the severity of the stenosis and the instability of the lesion. Unfortunately, in the earliest stages of CAS, stents and delivery systems were faulty, an appropriate antithrombotic regimen was not established, and treating physician technical competence was not ensured. Both procedural difficulties and unwanted complications led to the premature abandonment of CAS. Collaboration among neurologists, cardiologists, vascular surgeons, neurosurgeons, and interventional radiologists is crucial to select appropriate patients. The development of self-expanding stents, embolic protection devices, and a regimen of dual antiplatelet therapy led to the revival of CAS.

CAS has since gone from being the believed replacement for carotid endarterectomy (CEA), to the vascular procedure subject to intense scrutiny with more than 6500 patients studied in six large randomized clinical trials. Appropriate patient selection for surgical intervention and determining proper surgical intervention to treat carotid stenosis are goals of the currently ongoing Carotid Revascularization and Medical Management for Asymptomatic Carotid Stenosis Trial (CREST-2) trial. Today, practitioners offering CAS do so cautiously for a select population with understanding of the complications and risks and benefits profile.

The number and sequelae of the complications associated with CAS have been highlighted with multiple clinical trials but how to avoid and treat these complications has not received as much attention. This chapter looks at the some of the most commonly encountered complications associated with CAS and methods for complication avoidance and management.

Procedural Planning

Simple steps can be taken prior to the procedure to help reduce the complication rate associated with CAS. A thorough history should include a detailed account of any stroke history, in addition to vascular and cardiac history. Prior use of anticoagulation or antiplatelet therapy should be noted, as well as contraindications for such therapy. Patients should have a well-documented neurologic examination performed prior to the procedure. Physical examination should also include a pulse examination of potential access sites. Antiplatelet therapy with clopidogrel should be started 5 days prior to the procedure. Patients should receive a loading dose on the day of the procedure prior to CAS if they are not already on medication. Imaging studies including a bilateral carotid arterial duplex, computed tomography angiography (CTA), or magnetic resonance angiography (MRA) of the chest, neck, and brain should be performed to assess the contralateral internal carotid artery (ICA), vertebral arteries, aortic arch, the Circle of Willis, and other pertinent anatomy. The surgical approach should be established and the appropriate length sheaths, catheters, and wires should be available. Three-dimensional imaging reconstructions can help clarify the appropriate stent, diameter, and length. The interventionalist should ensure that appropriate devices are available for the procedure. The importance of procedural planning cannot be emphasized enough.

Access Difficulties

Access difficulty can present in extremely dilated aortic arches, aortic arches with severe atheroma with unrecognized ostial lesions of the common carotid or brachiocephalic arteries, and in those patients with tortuous vessels. An angled Glide catheter (Terumo, Somerset, New Jersey) and 0.035′′ Glidewire (Terumo, Somerset, New Jersey) are generally the initial choices to cannulate the innominate, right common, or left common carotid arteries. In difficult arch anatomy, particularly bovine arches, a reverse curve catheter such as a JB2 (Terumo Somerset, New Jersey), Vitek (Cook Medical, Bloomington, Indiana), or Simmons-1 (Terumo, Somerset, New Jersey) can be used (or SIM select or SIM2 [Cook Medical]) ( Fig. 44.1 ).

In the case of extremely dilated aortic arches, a sidewinder curved catheter such as a Simmons-3 (Terumo Somerset, New Jersey) can be used to access the brachiocephalic artery ( Fig. 44.2 ). With cannulating the right common carotid artery, the stabilizing introducer sheath should not be too close to the aortic arch because this will decrease the maneuverability of the catheter used to access the right ostium.

Tortuosity in the common carotid artery can be a hindrance to sheath or guide catheter placement. Access should be accomplished by placing a stiff wire, such as an Amplatz (Boston Scientific Marlborough, Massachusetts), in the external carotid artery as far as possible. The tip of the sheath or guide catheter should be secured in the common carotid artery approximately 1 cm below the bifurcation without advancing the introducer into the bifurcation. When the lesion of interest is in the distal common carotid or the external carotid artery is occluded, an Amplatz with a J tip and short (3 cm) floppy segment can be used. Another option would be to use a telescoping guiding sheath over a slip catheter (JB2, Simmons-1, or Vitek) over a stiff Glidewire (Terumo Somerset, New Jersey) to facilitate positioning of the sheath. When maneuvering the introducer sheath over the catheter to the carotid stenosis, if the sheath does not track easily over the catheter, the catheter should be removed and replaced with the sheath's inner introducer. The catheter can then be replaced once the sheath is moved into the appropriate position. Common carotid artery (CCA) tortuosity or a stenosis difficult to traverse can be crossed with a Glidewire and 5-French catheter. Be cognizant that when placing the introducer sheath in a long tortuous CCA, this might result in bifurcation displacement and kinking of the vessel complicating stenting. Advancement of the guide catheter or sheath should be done under fluoroscopic guidance or roadmap guidance ( Fig. 44.3 ). ICA tortuosity can also be overcome by using a 0.014′′ “buddy” guidewire to assist with straightening out the vessel and the use of a V18 wire to help aid guide catheter sturdiness.

Some anatomic limitations can impede the use of transfemoral access for CAS. Not only can diseased aortic arches and tortuous arch vessels preclude using transfemoral access, aortoiliac and femoral occlusive disease, previous vascular interventions in the groin, and obesity can make CAS with standard transfemoral access impossible. Older individuals (>70 years) have inferior outcomes with transfemoral CAS compared with CEA, probably because of the atheromatous burden leading to embolic events. Careful assessment of the aortic arch is important in the elderly population and may lead to alteration in access site. In such cases, transcervical access might be preferred. In a large meta-analysis of procedures using transcervical access, Sfyroeras et al. showed a technical success rate of 96% for 579 procedures performed. The incidence of transient ischemic attack (TIA), stroke, and death was 2.7%, 1.1%, and 0.41%, respectively. The transcervical approach was analyzed using both flow reversal with an arteriovenous shunt and no flow reversal for stroke incidence, and no difference was noted between the two groups.

The transcervical approach avoids having to navigate through potential atheromatous burden in the iliac arteries, aorta, and arch vessels and dislodging embolizing debris. Flow reversal creates a large arteriovenous shunt between the common carotid artery and ipsilateral jugular vein redirecting blood flow away from the internal carotid artery. The procedure can in most patients be done under local anesthetic. Full details of the transcervical approach with flow reversal are described elsewhere.

Alternatively, transradial approaches can be used to access the carotid artery if the femoral approach is not feasible. From the right side, this negates the need to traverse the aortic arch ( Fig. 44.4 ).

Crossing Preocclusive Stenotic Lesions

Wire selection is of paramount importance when crossing the stenosis for CAS. Wires larger than 0.018′′ should generally be avoided crossing the stenosis to decrease risk of embolization. If a smaller wire is being used to cross the stenosis, once the lesion is crossed, the wire should be exchanged for a 0.018′′ wire to ensure stability and easier advancement of the device required during stenting. Wire exchanges require repeat angiography because the wire stiffness can change the anatomy and presumed stenosis location. It is important to visualize the distal placement of the wire to avoid intracranial location with increased risk of injury to the vessel. The wire needs to be advanced distally enough to allow placement of the filter or protection device.

Difficulty placing embolic protection devices distal to the stenosis is more commonly encountered with filter devices as opposed to balloon embolic protection devices. The crossing profiles for filter devices with U.S. Food and Drug Administration (FDA) approval for use in CAS are 3.4–3.9 French as opposed to balloon devices, which are closer to 3 French. Filter embolic protection devices also have an abrupt change in stiffness between the filter and wire, which can limit trackability. Such difficulties are usually circumvented with predilation of the stenosis. In a study assessing technical difficulties crossing stenotic lesions, Powell et al. reported inability to cross the lesion in 29% of CAS cases using filter embolic protection devices. In 5% of those CAS cases, predilation still did not facilitate filter embolic protection devices to cross the stenosis. In all of these cases, CAS was successfully performed with balloon embolic protection devices. None of the CAS stenoses originally treated with balloon embolic protection devices was unable to be crossed or required predilation. This suggests that a tight lesion might be better treated with a balloon embolic protection as opposed to a filter device for distal protection, especially if the stenosis is narrower than 3.4 French. The MoMa device (Medtronic, Minneapolis, Minnesota) and balloon guide can allow flow reversal state instead of filter protection.

Predilation of stenoses should be performed selectively given the increased risk of periprocedural neurologic events. Nominal pressure should be used unless the lesion is heavily calcified and expected to recoil. Predilation time should be limited to a few seconds if the balloon attains its full shape quickly. Predilation time should only be prolonged (<120 seconds) if the balloon attains its full shape slowly. Preocclusive lesions might require serial predilation with a 1.5-mm or 2-mm balloon, followed by a 4-mm balloon. If the stent to be used does not pass easily through the stenosis after predilation with a 4-mm balloon, a 5-mm balloon should be used for additional predilation. Each additional predilation should be followed with an arteriogram. Only heavily calcified lesions should be postdilated and only if residual stenosis is detected by angiography or intravascular ultrasound (IVUS).

In tight lesions or severe tortuosity, embolic protection devices that are not attached to a wire and advanced independently over a wire might be preferable. Balloon embolic protection devices that advance independently over a wire, such as the GuardWire (Medtronic Minneapolis, Minnesota), have increased flexibility through highly stenotic lesion and tortuous anatomy.