Stenting the Critical Calyceal Carotid Bifurcation — A Technical<br />
Update

Case Report. The patient was a symptomatic 78-year-old male with a prior history of hypertension, noninsulin-dependent type 2 diabetes, coronary artery bypass graft surgery and coronary and peripheral percutaneous intervention. The patient had experienced an episode of right-sided weakness associated with visual field defects including blurring and speckling at the focus of vision. Brain magnetic resonance imaging showed moderate microangiopathy with no new signs of recent cerebrovascular accident. Magnetic resonance angiography showed a critical stenosis of the left internal carotid artery (LICA) with decreased flow into the distal internal carotid artery (ICA). He was referred for carotid angiography and possible endovascular therapy. Carotid angiography revealed a 90% proximal LICA stenosis (Figure 1) with diminished intracranial flow and significant supply of the left anterior cerebral artery (ACA) and middle cerebral artery through the ACA from the right internal carotid artery (RICA) (Figure 2). The patient agreed to participation in CREST (Carotid Revascularization Endarterectomy vs. Stenting Trial) and was randomly assigned to stent therapy.
A 5 Fr VTK catheter (Cook Inc., Bloomington, Indiana) was advanced into the left common carotid artery (LCCA) over a 0.038 inch Glidewire (Terumo Corp., Somerset, New Jersey). Angiograms were taken to define the anatomy of the bifurcation of the LCCA, and the VTK catheter, over the Glidewire, was advanced into the external carotid artery. The Glidewire was exchanged through the VTK catheter for a 0.035 inch SupraCore wire (Abbott Vascular, Santa Clara, California), and after removal of the VTK catheter, a 6 Fr Shuttle sheath (Cook) was advanced to the distal LCCA proximal to the bifurcation.
A 0.75 mg/kg intravenous bolus of bivalirudin was administered followed by a 1.75 mg/kg/hour infusion. The interventional equipment was prepared for use and included the following devices: Accunet Filter (Abbott Vascular), 3.5 x 30 mm Maverick 2 Rx balloon (predilatation, Boston Scientific Corp., Natick Massachusetts); RX Acculink™ 7–10 mm x 40 mm stent (Abbott Vascular); 5.0 x 20 mm Sterling balloon (postdilatation, Boston Scientific); Accunet retrieval catheter. In addition, a 2.0 x 30 mm Maverick 2 RX balloon and a ChoICE PT 0.014 inch moderate-support wire were prepared in the event of difficulty placing the embolic protection device (EPD).
To allow free head movement, which may assist in reducing ICA tortuosity, the head restraint was removed. The patient was asked to tilt his chin up as much as possible to extend the neck and was asked to rotate his head left and right to discern which rotation most straightened the course of the ICA.
A broad-tipped curve was shaped on the tip of the Accunet filter device and the tip of the filter wire was easily advanced across the lesion, but the filter was unable to even enter the 90º angulated ostium of the LICA without prolapsing of the filter wire transition point into the external carotid artery (ECA). The ChoICE PT wire was advanced to the LCCA, successfully crossed the lesion and was placed in the LICA. Further attempts at advancement of the Accunet filter remained unsuccessful despite the presence of the “buddy” wire and repetition of the patient’s head maneuvers (Figure 3). A Maverick 2 RX 2.0 x 30 mm balloon was advanced over the ChoICE PT wire into the lesion and slowly inflated to 10 atm for 10 seconds and then slowly deflated. The balloon was removed, but the Accunet filter was still unable to advance beyond the 90º turn despite further patient head maneuvering (Figure 4). In spite of multiple attempts, we were unable to advance the Accunet filter across the stenosis into the LICA. The Accunet filter was removed and an Emboshield soft wire (Abbott Vascular) was advanced without any difficulties alongside the ChoICE PT wire. The Choice PT wire was then removed and an Emboshield 6.0 mm filter (Abbott Vascular) was easily advanced to the LICA. A Maverick 2 Rx 3.5 mm x 30 mm balloon was advanced into the lesion and slowly inflated to 12 atm for 10 seconds and was then slowly deflated. An Acculink RX 7–10 mm x 40 mm stent was advanced into the lesion and deployed. A Sterling Mono 5.0 mm x 20 mm balloon was advanced into the stent and slowly inflated to 10 atm for 10 seconds and then deflated. The filter was then successfully retrieved. Postprocedural angiography showed a good result (Figure 4). The patient was discharged the following day.

Discussion
This case emphasizes the limitation of first-generation device technology when approaching more challenging carotid bifurcation anatomy. First-generation filter devices (Angioguard – Cordis, Accunet –Abbott Vascular and Filterwire – Boston Scientific) employ a fixed relation of the filter to the wire on which the filter is mounted. In contrast, in secondgeneration devices (Emboshield – Abbott Vascular and SpideRx – ev3, Inc., Plymouth, Minnesota), a bare wire is passed across the lesion over which the filter is then independently advanced. In the case described here, vessel tortuosity was not sufficient to prohibit consideration for carotid stenting and met eligibility criteria for the CREST study.¹ The Accunet filter was used under the CREST protocol. The technical problems associated with the device were unable to be managed by the additional maneuvers undertaken, and only by changing to a different embolic protection system could the case be completed. The decision to abandon the Accunet device in favor of an over-the-wire system was made only after prolonged and repeated attempts to pass the device and after careful consideration that this would result in a protocol violation. Patient safely became the prime concern.
In this case, the often useful effect of a buddy wire in reducing vessel angulation and tortuosity failed to facilitate EPD tracking. In addition, extending the patient’s neck and having him rotate his head from side to side was unhelpful. Similarly, “buddy” wire placement without predilatation with the small 2 mm balloon was ineffective. Although under ideal circumstances the EPD should be placed distal to the lesion before any dilatation, predilatation with a low-profile 1.5 mm or 2.0 mm balloon is rarely, if ever, associated with a neurological event. In very severe and complex lesions, attempts to pass the EPD device can result in complete obstruction and loss of flow. Accordingly, it is good practice to have a buddy wire and balloon readily available to “bail out” the situation should this occur. A very steerable hydrophilic wire such as the ChoICE PT is best suited for rapid lesion access. Similarly, it is good practice to keep the tip of the EPD wire across the lesion (if the tip has successfully crossed, but the body of the EPD cannot advance) to prevent loss of access until the buddy wire is fully across a very severe and complex stenosis.
All the above efforts failed in this case, and the Accunet device would still not track along the buddy wire. The situation was only able to be remedied by a change from a fixed-wire filter system (Accunet) to a bare-wire EPD system (Emboshield). Having the filter wire situated more distally within the ICA provides more support as well as allowing some degree of vessel straightening, which facilitates filter EPD tracking. Similarly, the SpideRx filter EPD (ev3, Inc.) is able to be tracked over any 0.014–0.018 inch wire, allowing for use of a variety of more steerable, trackable or supportive wires that can be advanced beyond the lesion and more distally within the ICA.
Alternative options exist for lesions that are difficult to wire. Advancing appropriately-shaped catheters through the guiding sheath so that the tip points into the ostium of the ICA can facilitate wire entry. Microcatheters have been described as being used to provide support to wires in crossing difficult lesions.² For difficulty crossing the lesion with an EPD, some operators have chosen to change over to a proximal occlusion device (if tolerated by the patient), while others have used a variety of buddy wires and predilatation techniques in order to deliver the filter and stent.^3,4

Conclusion
Patient safety and the minimization of adverse events remain the prime concern of neuroendovascular procedures. Complicated lesions require planning and preparation of all required equipment prior to encountering difficulties or problems. Older-generation devices are not easily tracked through critical calyceal carotid bifurcation lesions, necessitating a “safe” predilatation technique with buddy wire support or a change to a bare-wire system. This case highlights different techniques that allow for the safest passage of a filter EPD beyond a critical calyceal carotid bifurcation lesion.

References

1. Carotid Revascularization Endarterectomy vs. Stent Trial (CREST) – National Institutes of Health.
2. van den Berg J, Moll F. Microcatheter technique assists stenting of complex carotid stenosis. J Endovasc Ther 2002;9:381–383.
3. Kwon BJ, Han MH, Kang HS, Jung C. Protection filter-related events in extracranial carotid artery stenting: A single-center experience. J Endovasc Ther 2006;13:711–722.
4. Powell RJ, Alessi C, Nolan B, et al. Comparison of embolization protection device-specific technical difficulties during carotid artery stenting. J Vasc Surg 2006;44:56–61.