Cath Lab Digest

Abstract

Methods of cerebral embolic protection during carotid artery stenting focusing on the newest method, proximal occlusion, are discussed in this manuscript. Proximal occlusion devices achieve cerebral protection through flow reversal from the internal carotid artery into the arterial guide sheath that is the conduit for the deployment of devices across the carotid bifurcation. We review the literature and draw upon our experience-based opinion.

VASCULAR DISEASE MANAGEMENT 2012;9(1):E5–E12

Key words: carotid artery angioplasty and stenting, cerebral protection, embolic protection devices

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Introduction

Carotid artery angioplasty and stenting (CAS) is an alternative to carotid endarterectomy (CEA) for stroke prevention in symptomatic and asymptomatic carotid stenosis. The concerns of procedure-related embolic complications led to the emergence and acceptance of cerebral protection devices. There are 3 main types of devices for cerebral protection: distal occlusion balloons, distal filters, and proximal occlusion devices with and without flow reversal. Each approach possesses unique strengths and weaknesses.¹

Distal occlusion balloon systems (PercuSurge GuardWire system, Medtronic,² and TriActiv System, Kensey Nash) include a compliant, radiopaque-labeled, inflatable balloon that is advanced over a wire to the internal carotid artery (ICA), distal to the lesion. An export aspiration catheter is placed over the shaft of the guardwire to remove debris generated by the procedure. Advantages of this type of system include greater ease of traversing critically stenotic or tortuous lesions because of the low crossing profile of the balloon, along with flexibility and increased trackability.³ Known associated complications include vasospasm or dissection of the ICA, bradycardia, asystole, and hypotension due to stretch on the carotid sinus.³ Approximately 5% of the patients do not tolerate initial balloon occlusion,⁴ raising concerns that patients with severe contralateral carotid artery disease might not neurologically tolerate ICA occlusion. This type of device is cumbersome and complex to deploy and compromises visualization of the distal ICA owing to flow occlusion by comparison with filter-type devices.³

Filter-type distal embolic protection devices, which do not involve occlusion or reversal of cerebral blood flow, eventually replaced distal occlusion balloons as a means to provide cerebral protection. There are several different filter designs that each allow continuous antegrade flow and filtration of debris. Five filter-type devices have received FDA approval for use in the U.S., which are the Accunet with the Acculink stent (Abbott Vascular), the EmboShield with the Xact stent (Abbott), the Spider (ev3 Endovascular), the FilterWire EZ with the NexStent (Boston Scientific), and the AngioGuard with the Precise stent (Cordis).

Distal filters consist of a supporting wire made of nitinol and a basket composed of a polyurethane membrane that has 80 mm-130 mm pores. The diameter of the filter ranges from 3.0 mm-7.0 mm. The filter is connected to the distal end of a 0.014-inch wire with a floppy tip, which is used as a guidewire during the interventional procedure. The closed filter is advanced through the lesion and opened in the ICA, distal to the lesion. At the end of the procedure, a retrieval sheath is advanced and the filter is closed and removed from the artery.⁵ Filter protection devices generally have larger crossing profiles than occlusion balloon protection devices with an abrupt change in diameter between the floppy-tipped distal wire and the filter basket that can adversely affect trackability.³

Proximal occlusion devices work by stopping or reversing flow in the ICA. These types of devices include a long sheath catheter with a central working lumen that is connected to 2 balloons inflated to occlude the external carotid artery (ECA) and the common carotid artery (CCA), thereby allowing the entire procedure to be performed under complete cerebral protection. To achieve this type of protection (ie, to prevent embolization), there is a need to create complete cessation or reversal of flow in the ICA.¹ The MO.MA device (Invatec) and the Gore flow reversal system (W. L. Gore & Associates) are FDA-approved proximal occlusion devices.

By understanding the mechanisms of procedure-related thromboembolism and the advantages and disadvantages of the protection devices, operators can tailor the choice of device to patient-specific anatomy and lesion characteristics in order to reduce the risk of periprocedural stroke and improve the safety of CAS.