11 Carotid Artery Stenting with Distal Protection
General Description
Carotid artery revascularization is an effective modality of stroke prevention in selected patients with carotid stenosis. Carotid endarterectomy (CEA) is a well-established surgical method of revascularization. With the advancement of endovascular techniques and technology, protected carotid artery stenting (CAS) has become a viable alternative to CEA. There are different types of embolic protection from distal devices, such as filters and balloons, and proximal devices, such as balloon guide catheters and the Gore Flow Reversal System (Gore). Newer hybrid endovascular–surgical devices are also available for direct carotid artery access. Furthermore, CAS can also be utilized in the setting of acute ischemic stroke for tandem (extracranial and intracranial vessel occlusion) lesions.
Evidence for CAS Performed with Distal Protection
The Stenting and Angioplasty with Protection in Patients with High Risk for Endarterectomy (SAPPHIRE) study compared protected CAS to CEA in patients at high risk for surgical complications with > 50% symptomatic stenosis or > 80% asymptomatic stenosis. The study findings showed that CAS was an effective treatment option for this patient population. The 1-year rate of ipsilateral stroke or procedure-related or vascular death was 12.2% for CAS and 20.1% for CEA.
The Carotid Revascularization Endarterectomy versus Stenting Trial (CREST) randomized 2,502 patients with symptomatic or asymptomatic carotid stenosis (>50% stenosis on angiography or > 70% on ultrasonography) to CEA or protected CAS. The investigators found no significant difference in the rates of periprocedural stroke, myocardial infarction, or death in the treatment groups.
The asymptomatic carotid trial (ACT) randomized 1,453 patients with asymptomatic severe (70%–99%) stenosis and found that protected CAS was noninferior to CEA with 30-day stroke or death rates of 3.8% versus 3.4%, respectively.
Indications
CES is indicated for patients with symptomatic internal carotid artery (ICA) stenosis > 70% or asymptomatic ICA stenosis >80%. Other indications include the inability to tolerate general anesthesia during CEA, contralateral carotid occlusion or laryngeal nerve palsy, previous neck surgery or radiation therapy, restenosis after CEA, and poor neck mobility. CAS is also used for treatment of dissections and cases of acute stroke with tandem occlusions, as stated earlier. Medicare has specific requirements for CAS reimbursement.
Neuroendovascular Anatomy
The ICA normally originates from the common carotid artery (CCA) at the C3-4 or C4-5 level of the cervical spine. The artery may occur as low as T2 and as high as C1. The ICA is the largest of the two CCA branches. The carotid bulb (or sinus) forms a focal dilation and is the most proximal aspect of the cervical ICA. The diameter of the bulb is approximately 7.5 mm, compared to the CCA diameter of 7.0 mm and the ICA diameter of 4.7 mm distal to the bulb. The proximal ICA initially lays posterolateral to the external carotid artery (ECA), then courses medial to the ECA as it courses upward. The cervical ICA has no branches. Tortuosity and kinking or looping of the ICA occasionally occur, especially in older patients. Coiling or complete looping of the ICA occurs in 5%–15% of patients. One must always be vigilant for aberrant anatomy (i.e., proatlantal persistent vessels) that could be disrupted during stenting, resulting in posterior circulation stroke.
Periprocedural Medications
Dual antiplatelet therapy with aspirin (325 mg daily) and clopidogrel (75 mg daily) is prescribed for the prevention of platelet aggregation on the stent with resultant formation of an intraluminal thrombus during or after the stenting procedure. The regimen is started 5–7 days before the procedure for elective procedures. If that is not possible, a loading dose of aspirin (650 mg) and clopidogrel (600 mg) should be given early on the day of the procedure, followed by daily doses of aspirin (325 mg) and clopidogrel (75 mg). Dual antiplatelet therapy is maintained for 3 months after stent placement, at which point the clopidogrel is discontinued and the aspirin is continued indefinitely. Aspirin and clopidogrel serum responses should be monitored and therapeutic. Patients can be nonresponsive or allergic to clopidogrel. An alternative is ticagrelor (60 mg twice daily).
Intraprocedural thrombus formation is always a risk and systemic heparinization is administered during the procedure because of the risk of intraprocedural thrombus formation. A weight-based intravenous bolus of heparin aimed at an activated coagulation time of 250–300 seconds may limit thromboembolic complications. Administration of the heparin before crossing the stenotic lesion may limit thrombus formation on devices positioned within the ICA. For acute thrombus formation during the procedure, a glycoprotein IIb/IIIa inhibitor (e.g., eptifibatide) is utilized.
Hemodynamic instability sometimes occurs during carotid stenting and balloon angioplasty. Bradycardia, asystole, and hypotension are the most common events. During the procedure, asking the patient to perform a Valsalva maneuver (i.e., to cough) will usually reverse bradycardia. A good practice is to have a vasopressor (e.g., dopamine or phenylephrine) available, as well as atropine. We typically perform CAS with the patient in an awake state (i.e., conscious sedation) for accurate neurological assessment.
Specific Technique and Key Steps
Several clinical trials have demonstrated the efficacy of embolic protection devices in preventing intraprocedural ischemic complications. Using a distal embolic protection device, the key steps for CAS are as follows ( Fig. 11.1–11.6 , Video 11.1–11.6 ).
A 6 or 8 French (F) sheath is inserted in the femoral artery.
After the femoral angiogram has been performed to confirm the absence of any irregularity or dissection, a guide catheter is advanced over a curved wire (0.035-inch angled Glidewire, Terumo) into the aorta. This maneuver is completed under fluoroscopic guidance.
Depending on the arch anatomy, the guide catheter can be brought up directly over a 0.035-inch angled Glidewire or advanced over a 4–5F intermediate diagnostic catheter, such as a Vitek (Cook Medical) or Berenstein catheter (Cook Medical). Utmost care should be taken to prevent the wire, catheter, or guide from crossing the stenotic lesion.
Cerebral angiography is performed to obtain a baseline set of images of the intracranial vasculature.
Cervical carotid angiography with magnified working views of the carotid artery is obtained. Measurements of the degree of stenosis, length of stenosis, and diameters of the CCA and distal ICA are obtained for proper sizing of the stent.
Selection of the stent ( Video 11.1–11.6 ):
Closed-cell stent—Xact (Abbott Vascular) or Wallstent (Boston Scientific)—usually used for acute symptomatic ICA stenosis or with other high-risk feature (hemorrhage or plaque morphology (ulcerated).
Open-cell stent—Acculink (Abbott Vascular)—for tortuous anatomy.
High-radial-force stent—for a heavily calcified lesion.
Tapered stent—for discrepancy between the diameters of the ICA and CCA.
The distal embolic protection device is navigated through the stenosis up to the upper cervical ICA and deployed under fluoroscopy. The steps for deployment are different for different devices but usually involve unsheathing the device ( Video 11.1–11.6 ).
Once the filter has been deployed and under roadmapping guidance, the stent is advanced over the area of stenosis and deployed. Typically, a rapid exchange system is utilized. The stent is sized 1–2 mm beyond the diameter of the CCA ( Video 11.1–11.6 ).
Cervical carotid angiography is performed to assess post-stenting residual stenosis and the need for balloon angioplasty ( Video 11.1–11.6 ).
A noncompliant balloon is used to perform angioplasty poststent placement. The balloon is undersized by 1 mm less than the diameter of the ICA ( Video 11.1–11.6 ).
Intravascular ultrasound can be used to identify residual stenosis, residual debris within the lumen, or stent apposition to the artery wall ( Fig. 11.1 , Video 11.1 ).
The distal protection device is captured and removed utilizing a separate distal capture device (catheter).
A final (i.e., control) cerebral angiogram is always recommended to assess for smooth synchronized perfusion, looking specifically for delayed capillary filling or other larger occlusion (vessel dropout).
Device Selection
In the authors’ and editors’ practice, the following are the common set-ups and devices used for CAS with distal protection:
6 or 8F sheath.
6F guide catheter (i.e., Envoy XB catheter or Cook Shuttle, Cook Medical).
0.035-inch angled Glidewire.
Intermediate 5F-diagnostic catheter (Vitek).
Distal protection device (i.e., Emboshield NAV6 embolic protection device, Abbott or Gore).
Carotid stent (closed-cell Wallstent, Boston Scientific), (Mesh Covered Stent [ Fig. 11.2 , Video 11.2 ]).
Noncompliant balloon.
Distal capture device (protection device manufacturer-specific).
Continuous heparinized flush.
Pearls
One of the most technically challenging portions of CAS is placement of the guide catheter. The amount of purchase of a guide catheter in a stenotic carotid artery lesion is limited and often in the setting of difficult anatomy (bovine arch, dilated and calcified arch, and/or tortuous great vessels). A stiff, robust guide catheter (like those previously mentioned) is necessary so the catheter does not herniate downward into the aortic arch when the stent is advanced into position.
For crossing the lesion, a steerable 0.014-inch microwire is used. Some angulation of the tip of the microwire is recommended for ease of guidance through the area of stenosis. Microwire shaping conforms to the unique anatomy of the patient’s lesion.
Looped or tortuous anatomy of the ICA may complicate navigation into the distal cervical ICA. The wire is passed to a point in the cervical ICA that enables passage of the stent safely beyond the stenosis. A stiffer wire might be required. Consideration is given to the use of a proximal protection guide catheter (MoMa guide catheter) in this scenario.
For stent placement, we recommend selecting an osseous landmark (i.e., a cervical vertebrae) to be the distal landing site of the stent. Without such a landmark, the roadmap may be unreliable because of vessel deformation that occurs with positioning of the stent or guide catheter or because of patient motion.
If the stent is not easily passed through the lesion over the microwire, pre-stent angioplasty is performed with an undersized balloon to prevent plaque rupture ( Fig. 11.3 , 11.4 , Video 11.3 , 11.4 ).
For closed-cells stents, a malpositioned stent may be recaptured if partially deployed (up to 80% for most closed-cells stents). Otherwise, various telescoping stents may be required.
During recapture of the distal protection device, difficulty may be encountered when navigating the retrieval sheath through the stent. This is particularly problematic if the interventionist is using an open-cell stent. The patient may be asked to turn his or her head in either direction as passage of the retrieval catheter through the stent is attempted again. Careful monitoring for stent dislodgement under continuous fluoroscopy is necessary until the protection device has been withdrawn.
Case Overview: CASE 11.1 Internal Carotid Artery Stenting and Angioplasty Use of Intravascular Ultrasound
A 71-year-old male presented with transient numbness and tingling on the left upper and lower extremities. His past medical history was relevant for hypertension, diabetes mellitus, hypercholesterolemia, coronary artery disease, and previous left carotid artery stenosis treated with stenting and angioplasty. Patient is taking aspirin and Clopidogrel for his coronary disease.
Carotid Doppler ultrasound and computed tomography angiography demonstrated severe stenosis (90%) of the right internal carotid artery (ICA). Carotid Doppler ultrasound showed velocities of 360/160 cm/s.
Procedure
The patient underwent right carotid artery angioplasty and stenting with a distal filter protection device. The procedure was performed under conscious sedation and through a right femoral artery approach. 5,000 units of heparin were given to obtain an activated clotting time more than 250.
Related posts:
Stay updated, free articles. Join our Telegram channel
Full access? Get Clinical Tree
