Introduction
Stenting of supra-aortic vessels has become a reasonable alternative or sometimes the treatment of choice for cases of athero-occlusive disease of the carotid, subclavian, innominate, and vertebral arteries. Protection from distal embolic debris or thrombus remains critical while performing stenting and angioplasty. The investigators of the Stenting and Angioplasty with Protection in Patients at High Risk for Endarterectomy (SAPPHIRE) trial and the Carotid Revascularization Endarterectomy versus Stent Trial (CREST) demonstrated similar long-term outcomes for endovascular carotid revascularization versus surgical carotid endarterectomy (CEA). The utilization of carotid artery stenting and angioplasty (CAS) in high-risk patients has continued to increase since the publication of the CREST results. The use of embolic protection devices in SAPPHIRE and CREST is thought to have led to lower stroke rates than those in earlier CAS trials. In a systematic analysis by Kastrup et al. of 2537 patients who underwent CAS procedures without protection devices versus 896 CAS procedures with protection devices, stroke rates were lower in the group with protection devices. Similarly, a meta-analysis by Garg et al. reported benefit with use of embolic protection devices. Technological advances continue to improve the safety and efficacy of CAS procedures with the more recent Safety and Efficacy Study for Reverse Flow Used During Carotid Artery Stenting Procedure (ROADSTER) demonstrating the lowest stroke rates of any trial. With the results of these trials, performing CAS with embolic protection devices has become the standard of care.
The decision to proceed with CAS versus CEA is multifactorial. Patient comorbidities as well as anatomical high-risk criteria play a significant role. A detailed discussion on selection criteria for patients undergoing CAS is beyond the scope of this chapter; however, there are anatomical factors that are associated with higher complication rates in CAS procedures that must be taken into account. In our study of patients undergoing CAS for symptomatic disease, carotid tortuosity and difficult distal landing zones were two anatomical factors associated with higher complication rates during CAS procedures. At our institution, the Buffalo Risk Assessment Scale ( Table 45.1 ) is used to aid in patient selection.
| Variable | Points |
|---|---|
| Carotid tortuosity (any) | 2 |
| Difficult distal landing zone | 2 |
| Concentric calcification | 1 |
| Carotid pseudo-occlusion | 1 |
| Difficult femoral access | 1 |
| NIHSS Score ≥10 | 1 |
| Renal disease | 1 |
| Maximum scale points | 9 |
| Total score | |
| BRASS I (low risk) | 0–2 |
| BRASS II (moderate risk) | 3–4 |
| BRASS III (high risk) | 5–9 |
Types of Embolic Protection: Proximal, Distal, and Complete Flow Reversal
Patient anatomy and lesion morphology are critical in selecting an embolic protection device. Embolic protection devices can be categorized into proximal embolic protection, distal embolic protection, and complete flow reversal devices or systems. (Flow reversal will be discussed in Chapter 48 : Transcarotid Artery Revascularization With the ENROUTE Transcarotid Neuroprotection System). Proximal embolic protection focuses on flow arrest by inflating a balloon in the common carotid artery (CCA) and/or external carotid artery (ECA), thus limiting or arresting anterograde flow in the internal carotid artery (ICA) and preventing distal emboli. Proximal embolic protection is advantageous because it allows the surgeon to cross stenotic lesions under flow arrest, especially when these lesions may require significant guidewire manipulation. In one meta-analysis comparing distal protection with a filter device with proximal protection, proximal protection was associated with a lower incidence of diffusion restriction on magnetic resonance imaging evaluation. However, the flow arrest approach for proximal protection relies on intracerebral collateral circulation, and proximal occlusion can lead to ischemic complications. Additionally, angiographic assessment cannot be performed once flow arrest has been instituted. Periodic deflation and inflation of the balloon allow intermittent anterograde flow and for angiographic assessment but can compromise distal protection.
Options for proximal protection include balloon guide catheters (Concentric or FlowGate; Stryker Neurovascular, Fremont, California) and the MoMa device (Medtronic, Minneapolis, Minnesota). These are typically 9-French systems. Balloon guide catheters are used when the lesion extends into the CCA and the plaque is considered unstable or there is concern for intraluminal thrombus. Balloon inflation allows advancement of a filter wire (0.014″) across the lesion under near flow arrest (the ECA is not occluded). Subsequently, the filter can be deployed to aid embolic protection. Intermittent inflation and deflation allows restoration of flow to prevent ischemic complications while the filter adds protection once the balloon is deflated. The MoMa device is best suited for lesions isolated to the ICA with unstable plaque or intraluminal thrombus. This is a two-balloon system that allows the lesion to be crossed under complete flow arrest (ECA occluded) with a 0.014″ wire. We prefer to use the MoMa device for symptomatic lesions. The investigators of the Proximal Protection with the MoMa Device During Carotid Stenting (ARMOUR) trial demonstrated the safety and efficacy of the MoMa device with an overall stroke rate of 1.9% with no strokes occurring in symptomatic patients. Additionally, the ROADSTER investigators have shown a similar low stroke rate of 1.4%, demonstrating the safety of proximal protection and flow reversal. Proximal protection is our choice when there is distal cervical ICA tortuosity that precludes safe landing of a filter device ( Fig. 45.1 ). As stated previously, these anatomical factors can lead to higher complication rates. Use of the MoMa device is limited by the fact that establishing proximal occlusion in the ECA and CCA requires that the stenotic lesion not extend into the CCA. Additionally, proximal protection relies on good intracranial collateral circulation. Ischemic complications can occur secondary to prolonged occlusion time and blood pressure management is critical while using proximal protection devices. Care must be taken when using these devices because balloon inflation can lead to dissection.
Distal embolic protection devices are filter devices. Distal occlusion of the ICA with a balloon can also be used; however, this is less common. Filter devices have become increasingly used for both symptomatic and asymptomatic carotid stenoses. Each system is based on a 0.014″ guidewire for access past the stenotic lesion. Deployment is preferred in the straight segment of the ICA, usually at the level of the C1 vertebra. Filter devices are available in different sizes ( Table 45.2 ). The benefit of this system for the surgeon is particularly important in patients who do not have good collateral circulation and cerebrovascular reserve. In cases of insufficient collateral flow, the distal filter device allows preservation of flow during the procedure. When approaching a carotid lesion, understanding the access site is paramount for planning. Type of aortic arch, CCA/ICA tortuosity, and morphology of the lesion (isolated to the ICA versus combined CCA/ICA, plaque versus thrombus) are taken into consideration before selecting an embolic protection device. For example, type III aortic arches and tortuous proximal CCAs require more flexible catheters and devices. Proximal protection in these situations may not be feasible. Low profile, flexible filter devices allow easier maneuverability into the more distal carotid artery and safe deployment prior to angioplasty and stent deployment. In addition, surgeons must take into consideration the type of stenosis and lesion that they have to manage. Low-profile, soft-tipped flexible devices are ideal because they allow navigability without the constraint of damaging the vessel wall or disturbing the plaque burden. Moreover, these devices can be used with smaller (6-French) systems ( Tip Box 45.1 ).
