New Transcarotid Stenting Procedure
By Jeffrey Jim, MD, MPHS, FACS, and Ignacio Leal, MD, PhD, RPVI
As the US population ages, the prevalence of cardiovascular disease will continue to increase.1 Therefore, the number of elderly patients requiring carotid revascularization for future stroke risk reduction likely will continue to increase as well.
Current practice guidelines recommend revascularization for select patients with symptomatic stenosis of 50% to 99% and asymptomatic stenosis of 60% to 99% of the internal carotid arteries.2 In choosing the appropriate revascularization procedure, individual patient characteristics, including advanced age, need to be carefully considered.
Carotid endarterectomy (CEA), the traditional open surgical procedure, remains the gold standard for carotid revascularization.3,4 However, over the past two decades, carotid angioplasty and stenting (CAS) has emerged as a viable and less invasive option.
Despite the publication of multiple large clinical trials, the clinical efficacy and effectiveness of these two procedures continue to be debated.5,6 However, there is clear utility for CAS in patients considered at high risk of CEA (see sidebar below).
Several factors likely contribute to the higher stroke rates seen with CAS. It is hypothesized that the use of transfemoral arterial access and the need for “crossing the lesion” play an important role.7 In traditional CAS, arterial access is obtained through the common femoral artery. Prior to placing a stent in the internal carotid artery, manipulations with wires, catheters, and sheaths in the aortic arch and the common carotid artery are required. In most patients with atherosclerotic disease, these tortuous and calcified proximal arteries are a potential source of atherosclerotic debris that can embolize and cause a stroke.
A wire and a filter device also must be passed through the internal carotid artery stenosis (a step referred to as crossing the lesion) prior to stent placement. This maneuver also is associated with significant embolic potential.
It is thus inferred that eliminating these two components of CAS may lead to significantly reduced stroke rates.
Minimizing Surgical Risk
The Silk Road procedure is performed through a small transverse incision just above the clavicle. This can be done under local anesthesia, avoiding the need for general anesthesia. Direct surgical exposure of the common carotid artery eliminates the need for aortic arch manipulation and its associated risk of embolization. The risk of cranial nerve injury at this level of dissection is significantly decreased compared with standard CEA.
During carotid manipulation, the proximal common carotid artery temporarily is occluded, allowing the cross-perfusion pressure essentially to invert (or reverse) flow from the internal carotid artery to the low-pressure common femoral vein. The flow controller also allows the operator to increase, decrease, or arrest flow at the push of a button. This dynamic flow reversal especially is important during crucial portions of the procedure, such as delivering the stent across the lesion. An inline filter captures any potential debris and prevents migration into the venous system.
With only several centimeters between the access site at the base of neck and the carotid lesion, the stent can be placed expeditiously to minimize procedure time.
The Investigation of Transcarotid CAS With Dynamic Flow Reversal in Subjects With Significant Extracranial Carotid Stenosis (ROADSTER) trial currently is enrolling patients in select centers throughout the United States, with additional sites in the European Union. It is a prospective, single-arm, multicenter clinical trial evaluating the use of the Silk Road Neuroprotection System. The study is enrolling both symptomatic (> 50% stenosis) and asymptomatic (> 70% stenosis) patients who are at high risk of complications from CEA. Patients must be at least 75 years old to participate, highlighting the procedure’s potential benefit in the geriatric population.11
Compared with a younger cohort, elderly patients tend to experience a higher rate of complications with various surgical procedures. It is widely believed that percutaneous interventions tend to be safer for elderly patients. However, the available data suggest that CAS may not be recommended for older patients because of the higher risk of periprocedural stroke12-14 stemming from elderly patients’ tendency toward heavily calcified aortic arches and other unfavorable anatomic characteristics (eg, aortic arch elongation, proximal stenoses, vessel tortuosity) that increase the difficulty of performing standard transfemoral CAS.15,16 Furthermore, older patients may have poor cerebral reserve, making them more sensitive to minor cerebral emboli.17
With these factors in mind, the Silk Road procedure provides an ideal solution, as it avoids the need for difficult arch manipulation, with a low rate of cerebral embolization.
Anticipating ROADSTER Trial Results
In choosing an appropriate procedure, individual patient characteristics need to be considered. For those with high-risk factors, including advanced age, the Silk Road procedure may prove to be the best choice, as it combines the advantages of both CEA and CAS while minimizing potential complications.
Data from the ROADSTER trial will support premarket approval and FDA clearance of the Silk Road Neuroprotection System. It is anticipated that the ROADSTER trial will complete enrollment in 2014. Until FDA approval, the procedure remains available only at the sites participating in the clinical trial.
— Jeffrey Jim, MD, MSPH, FACS, is an assistant professor of surgery at Washington University School of Medicine in St Louis.
— Ignacio Leal, MD, PhD, RPVI, is a consultant vascular surgeon in the vascular and endovascular surgery section of Complejo Hospitalario de Toledo in Spain.
CMS Criteria for High Surgical Risk Patients
• congestive heart failure class 3/4;
• left ventricular ejection fraction < 30%;
• unstable angina;
• contralateral carotid occlusion;
• recent myocardial infarction;
• previous CEA with recurrent stenosis;
• prior radiation treatment to the neck; and
• other conditions that were used to determine patients at high risk of CEA in the prior carotid artery stenting trials and studies, such as ARCHER, CABERNET, SAPPHIRE, BEACH, and MAVERIC II.
2. Ricotta JJ, AbuRahma A, Ascher E, Eskandari M, Faries P, Lal BK. Updated Society for Vascular Surgery guidelines for management of extracranial carotid disease: executive summary. J Vasc Surg. 2011;54(3):832-836.
3. North American Symptomatic Carotid Endarterectomy Trial Collaborators. Beneficial effect of carotid endarterectomy in symptomatic patients with high-grade carotid stenosis. N Engl J Med. 1991;325(7):445-453.
4. Executive Committee for the Asymptomatic Carotid Atherosclerosis Study. Endarterectomy for asymptomatic carotid artery stenosis. JAMA. 1995;273(18):1421-1428.
5. Brott TG, Hobson RW 2nd, Howard G, et al. Stenting versus endarterectomy for treatment of carotid-artery stenosis. N Engl J Med. 2010;363(1):11-23.
7. Verzini F, Cao P, De Rango P, et al. Appropriateness of learning curve for carotid artery stenting: an analysis of periprocedural complications. J Vasc Surg. 2006;44(6):1205-1212.
8. Leal I, Orgaz A, Flores A, et al. A diffusion-weighted magnetic resonance imaging-based study of transcervical carotid stenting with flow reversal versus transfemoral filter protection. J Vasc Surg. 2012;56(6):1585-1590.
9. Pinter L, Ribo M, Loh C, et al. Safety and feasabiliity of a novel transcervical access neuroprotection system for carotid artery stenting in the PROOF study. J Vasc Surg. 2011;54(5):1317-1323.
10. Kolvenbach RR. A specialized device for performing CAS via a cervical approach with flow reversal (FAST-CAS system): early results from the PROOF trial. Presented at: the 2012 Veith Symposium; November 14-18, 2012; New York, NY.
11. Safety and efficacy study for reverse flow used during carotid artery stenting procedure (ROADSTER). In: ClinicalTrials.gov. Bethesda, MD: National Library of Medicine. http://clinicaltrials.gov/show/NCT01685567: NCT01685567.
12. Jim J, Rubin BG, Ricotta JJ 2nd, et al. Society for Vascular Surgery (SVS) Vascular Registry evaluation of comparative effectiveness of carotid revascularization procedures stratified by Medicare age. J Vasc Surg. 2012;55(5):1313-1321.
13. Bonati LH, Fraedrich G, Carotid Stenting Trialists’ Collaboration. Age modifies the relative risk of stenting versus endarterectomy for symptomatic carotid stenosis—a pooled analysis of EVA-3S, SPACE and ICSS. Eur J Vasc Endovasc Surg. 2011;41(2):153-158.
14. Voeks JH, Howard G, Roubin GS, et al. Age and outcomes after carotid stenting and endarterectomy: the Carotid Revascularization Endarterectomy Versus Stenting Trial. Stroke. 2011;42(12):3484-3490.
15. Bazan HA, Pradhan S, Mojibian H, Kyriakides T, Dardik A. Increased aortic arch calcification in patients older than 75 years: implications for carotid artery stenting in elderly patients. J Vasc Surg. 2007;46(5):841-845.
16. Lam RC, Lin SC, DeRubertis B, Hynecek R, Kent KC, Faries PL. The impact of increasing age on anatomic factors affecting carotid angioplasty and stenting. J Vasc Surg. 2007;45(5):875-880.
17. Chaer RA, Shen J, Rao A, Cho JS, Abu Hamad G, Makaroun MS. Cerebral reserve is decreased in elderly patients with carotid stenosis. J Vasc Surg. 2010;52(3):569-574.