Preprocedural Planning
Carotid ultrasonography (US) and transcranial Doppler or transcranial color-coded US may be useful for diagnosis, risk stratification, peri-interventional monitoring, and follow-up of patients with carotid artery disease who undergo carotid artery stenting (CAS). [15] There is growing interest in the application of optical coherence tomography (OCT) to CAS. [16, 17]
Equipment
Listed below are the standard equipment and materials needed for CAS. All interventionalists who are performing percutaneous carotid interventions should choose their equipment in accordance with their personal preferences and with the local availability of specific materials and devices.
Access kit
Access can be obtained using a micropuncture kit (Cook, Inc). This kit consists of a 21-gauge needle for obtaining access to the vessel, Torq-Flex® wire, and a coaxial catheter.
Guide wires
The following two wires can be used:
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0.035-in. hydrophilic guide wire (Terumo) to access the aortic arch
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0.014-in. hydrophilic guide wire (Spartacore) to cross the lesion
Introducer sheaths
A 6-French access sheath can be used initially, followed by a 6-French long guiding sheath system.
Catheters
To gain access to the aortic arch and advance the guide wire through the carotid lesion, complex catheter manipulations may be required, especially if the patient has a tortuous anatomy. Catheters with varying degrees of angulation assist in minimally traumatic catheter passage. Available catheters include the following:
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JB-2 catheter (Cook, Inc)
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SIM 1 catheter (Cook, Inc)
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SIM 2 catheter (Cook, Inc)
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H1 catheter (Cook, Inc)
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VTK catheter (Terumo)
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Glide vertebral catheter
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Simmons catheter
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Mani catheter
Balloon systems
There are two main types of balloon systems: coaxial and monorail. For carotid interventions, monorail balloons can be used, with predilation of the lesion with a 2- or 3-mm balloon.
The balloon length is chosen according to the length of the stenotic lesion. To reduce the risk of atheroembolization, poststent dilation is generally avoided. If such dilation is required, a 5- or 6-mm balloon is used, depending on the diameter of the stent and the diameter of the stenotic lesion.
Stents (balloon-expandable and self-expanding)
There are two basic types of stents: balloon-expandable and self-expanding.
Balloon-expandable stents are mounted on a balloon catheter and passively enlarged to the desired diameter at the implantation site by dilating the balloon. They are better suited for proximal carotid artery and innominate artery lesions and offer greater precision during CAS. Their collapsed diameter is slightly larger than that of self-expanding stents; therefore, it is often difficult to cross a lesion with them unless the stenosis is predilated. The Express® stent (Boston Scientific) is the available balloon-mounted stent for carotid artery lesions.
Self-expanding carotid stents are used as a minimally invasive alternative to carotid endarterectomy (CEA). They open actively after being released from the delivery system. Their self-expanding character depends either on the braiding structure or on the type of alloy (usually nitinol or stainless steel). Commercially available self-expanding stents include the following:
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Carotid WALLSTENT ® (Boston Scientific)
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Nexstent ® (Boston Scientific)
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Precise ® (Cordis)
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Protege ® (ev3)
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Xact ® (Abbott)
Cerebral protection devices
The purpose of cerebral protection devices (CPDs) is to capture atherosclerotic emboli during catheter manipulation, angioplasty, and stenting. The risk of atheroembolization is greatest during balloon angioplasty of the stenosis and when the lesion is crossed by a wire. Different types of CPDs are commercially available, as follows:
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GuardWire ® temporary occlusion and aspiration system (Medtronic) - This is available in two balloon sizes, 2.5-5 mm and 3-6 mm, on a 0.014-in. wire system
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GORE Neuro Protection System (W. L. Gore & Associates; previously called Parodi Anti-Embolic System) - This system, based on the hemodynamic principle of reversal of internal carotid artery (ICA) blood flow with common carotid artery (CCA) occlusion, comes with a set of two balloons, one placed in the external carotid artery (ECA) and the other in the CCA; when both balloons are inflated, backbleeding generally occurs from the ICA
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Filterwire EZ ® embolic protection system (Boston Scientific) - The basic mechanism is filter-based; it is based on a 0.014-in. wire system
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Angioguard RX ® emboli capture guide wire system (Cordis)
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RX Accunet ® embolic protection system (Abbott)
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Emboshield NAV6 ® embolic protection system (Abbott)
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Spider FX ® embolic protection device (ev3)
Patient Preparation
Anesthesia
Conscious sedation and local anesthesia are preferred so as to permit continuous monitoring of the patient’s neurologic status. During balloon inflation, bradycardia and hypotension may occur; therefore, continuous cardiac monitoring and intra-arterial blood pressure monitoring are performed in all patients who undergo CAS.
Positioning
Carotid stenting procedures are performed in a hybrid, fixed C-arm operating room where multiplanar views are easily obtained. The patient is supine, with the head turned toward the opposite side. The operating surgeon usually stands on the patient's right side. Extra table length is added at the foot of the table to ensure that all wire lengths can be handled easily in a sterile field.
Monitoring & Follow-up
The 2018 guidelines from the Society for Vascular Surgery (SVS) recommended that after CAS, surveillance with duplex US should be carried out at baseline and every 6 months for 2 years and annually thereafter until the patient is stable (ie, until no restenosis or in-stent restenosis [ISR] is observed in two consecutive annual scans). [18] The first duplex study should be done soon after the procedure (preferably ≤ 3 months) to establish a posttreatment baseline. Surveillance should be maintained at some regular interval (eg, every 2 years) for the life of the patient.
For patients undergoing CAS who are diabetic, have aggressive (type IV) ISR patterns, have previously been treated for ISR, have previously undergone cervical irradiation, or have heavy calcification, the SVS recommended, in addition to the baseline duplex US, surveillance with duplex US every 6 months until a stable clinical pattern is established, and then annually afterward. [18]
The SVS recommended that post-CAS duplex US include at least the following assessments [18] :
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Doppler measurement of peak systolic velocity and end diastolic velocity in the native CCA; in the proximal, middle, and distal stent; and in the distal native ICA; modified threshold velocity criteria should be used to interpret the significance of these measurements after CAS
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B-mode imaging should be used to supplement and to enhance the accuracy of velocity criteria to estimate the severity of luminal narrowing
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Key steps in carotid stenting. Image courtesy of Kurt Mansor, Jobst Vascular Institute.
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Images show vessel before and after carotid artery stenting. Image courtesy of Cheong Lee, MD.
