Abstract

Background:We tested the feasibility of a mandated multidisciplinary carotid revascularization board (MDCB) to review, approve and monitor all carotid artery and stenting (CAS) procedures and outcomes at our institution.

Methods:The board was composed of vascular surgeons, cardiologists, interventional neuroradiologists, neurosurgeons, and neurologists, who met weekly to facilitate an evidence-based, consensus recommendation to ensure appropriate CAS referral.

Results:The board successfully reviewed and continues to review and approve all CAS procedures at our center. Of the 69 patients considered high risk for standard surgical treatment, 42 patients were symptomatic and 27 patients were asymptomatic. Their mean age was 70.5-year-old and the median degree of stenosis was 79%. In the 74 procedures, periprocedural complications occurred at the following rates: 2.7% death, 2.7% major stroke, 2.7% minor stroke, and 2.7% myocardial infarction (MI) within 30 days of the procedure. At 1 year the primary endpoints of ipsilateral stroke and neurovascular-related death were observed in 8.1% and 2.7% of the patients, respectively. At mean follow-up of 21 months, 18.8% of the patients (13/69) had died (including all causes), and 14.5% (10/69) experienced stroke (including nontarget strokes). Target vessel revascularization was needed in 2.9% patients.

Conclusions:A mandated multidisciplinary carotid revascularization board MDCB is feasible and potentially advantageous in real clinical practice. It establishes a model for accountable care by providing a mechanism for institutional oversight, credentialing operators, quality review, standardizing care, cost containment and eliminating the “subspecialty silo mentality.”

Keywords: Carotid angioplasty, multidisciplinary review board, stenting

INTRODUCTION

Carotid angioplasty and stenting (CAS) has emerged as a potentially less invasive alternative to carotid endarterectomy (CEA.) Based primarily on the results of the Stenting and Angioplasty with Protection in Patients at High Risk for Endarterectomy (SAPPHIRE) trial published in 2004, the Food and Drug Administration (FDA) approved the use of CAS with protection device in certain patients at high surgical risk for CEA.[ 10 24 ] The investigators allowed the interventionalist or the surgeons to decide if the patient is at high surgical risk at their own discretion in the SAPPHIRE trial which is subject of much controversy. High surgical risk conditions include medical comorbidities precluding safe surgery such as severe cardiopulmonary disease, and specific anatomical high-risk factors (i.e. previous neck irradiation, prior CEA, high carotid bifurcation with plaque extension into the inaccessible distal internal carotid artery, tandem lesions or contra-lateral carotid occlusion). These high surgical risk indications are often misinterpreted and subject to significant interobserver variation.

Over the last 10 years, there have been multiple randomized prospective trials investigating the efficacy of CAS versus CEA in standard risk patients.[ 4 13 16 23 ] The results of these trials have generated debate and have often arrived at different conclusions. The Carotid Revascularization Endarterectomy Versus Stenting Trial study (CREST), the largest prospective study conducted to date comparing carotid artery stenting (CAS) to CEA, demonstrated that CAS and CEA had similar safety and long-term outcomes for standard-risk patients with symptomatic and asymptomatic carotid artery disease.[ 4 ] The composite major adverse events (MAE) death, stroke and MI were similar for CAS and CEA, but CAS was associated with slighter higher risk of stroke and CEA was associated with higher risk of MI. Post-CREST, there is no international consensus on stenting for carotid disease and the various subspecialty groups have not agreed upon practice guidelines. However, the American Heart Association (AHA), the European Society for Vascular Surgery (ESVS) and the UK National Institute for Clinical Excellence (NICE) all recommend that the decision to perform CAS should be undertaken by a multidisciplinary group. None of the organizations provide a specific outline or framework to accomplish such a multidisciplinary format and there is little evidence in the literature to support the feasibility of such a group.

In the midst of healthcare reform with increasing scrutiny[ 6 ] of procedures and subspecialty care, physicians are confronted with significant questions regarding the best application of CAS. There is a delicate balance between patient safety, quality care, cost and the application of new minimally invasive innovations such as CAS. Institutional due diligence and regulatory compliance often competes with subspecialty marketing and the external influences of business and industry. Therefore, at our institution all patients considered for CAS were reviewed by a multidisciplinary carotid revascularization board (MDCB). The group was composed of vascular surgeons, neurosurgeons, interventional neuroradiologists, neurologists, and cardiologists and served as an institutional “checks and balances” for CAS. In this manuscript, we review the formation of the MDCB and the results of the first 69 high surgical risk patients who underwent CAS with the use of an embolic protection device as recommended by the MDCB.

MATERIALS AND METHODS

Development of the mandated multidisciplinary carotid revascularization board

The MDCB was formed by the division heads of vascular surgery, cerebrovascular neurosurgery, stroke neurology, interventional neuroradiology, and cardiology and was approved by the respective chairs, and the chief medical officer of our multispecialty group practice.

The primary goals of the MDCB were: 1) To ensure the appropriateness of all CAS procedures, and 2) to establish and maintain high-standards for the interventionalists performing CAS procedures. This MDCB was established in 2004 when the carotid stenting field was in its infancy. The MDCB was an initiative taken by the physicians and administration had no dictation in this matter. It was a pure outcome improvement endeavor without any financial perspective to decision-making process.

The MDCB founding committee established the methods of decision making for CAS procedures, described the experience necessary for receiving institutional privileges for the performance of CAS procedures, and developed methods and processes for quality review, including morbidity and mortality for all CAS procedures. It was mandated to have all the cases reviewed by MDCB before attempting CAS, but participation in the board was voluntary.

Case review by the mandated multidisciplinary carotid revascularization board

The MDCB facilitated an evidence-based approach. This board was established in 2004. Since the advent of the MDCB at our institution, all carotid artery stenting procedures have been reviewed and approved by the board. In instances where high-level evidence was not applicable to the clinical scenario, the board relied on the accumulated experience and clinical judgment of the group to make a consensus recommendation. The board met weekly and reviewed the pertinent clinical and radiological data on all patients referred for CAS.

The clinical presentation was carefully scrutinized to determine the important variables [ Table 1 ]. Radiographic imaging was reviewed to assess the degree of stenosis according to the North American Symptomatic Carotid Endarterectomy Trial (NASCET) criteria.[ 2 17 ] Angiographic features associated with increased procedural risk were recorded such as the presence of severe ulceration, presence of concentric calcification, tortuous aortic arch anatomy or tortuosity of the internal carotid artery[ 10 ] [Figures 1 – 7 ]. Noninvasive imaging such as carotid duplex study, magnetic resonance angiography (MRA), computed tomography angiography (CTA) as well as digital subtraction angiography (DSA) were reviewed and correlated. Intracranial collateral circulation based on MRA or DSA was carefully reviewed. Two concordant noninvasive tests were analyzed prior to making a revascularization recommendation. If there was significant discrepancy between the noninvasive studies, DSA was recommended. The inclusion and exclusion criteria for CAS were reviewed by the MDCB and the specific indications and or contraindications ascertained. The technical feasibility, periprocedural risk and potential outcomes were discussed. Life expectancy of the patients was considered and procedures were performed only on patients assessed to have an estimated life expectancy of 2 years. Since the decision about treatment modality was taken by the MDCB these patients were not included in any trial where they would get randomized. The steps of a case review and approval for carotid stenting are provided in Figure 8 . A prospective registry of only the patients who underwent carotid stenting was kept for analysis. Data of patients who did not undergo carotid stenting was not recorded.

Table 1

Variables

Figure 1

Aortic arch injection demonstrates a type III arch. A type III arch is technically more difficult to catheterize and obtain a stable guide catheter placement

Figure 2

Coronal CTA indicates a heavily calcified left internal carotid artery lesion associated with a tortuous medially located distal ICA. In addition, the contralateral internal carotid artery is occluded

Figure 3

Axial CTA of same patient with heavily calcified left internal carotid artery lesion. Concentric calcification is an angiographic high risk feature for CAS

Figure 4

(a, b) Native images of the same patient undergoing CAS with placement of buddy wire for support and the emboli protection device in the tortuous portion of the distal ICA. The calcification and the tortuosity make navigating the stent difficult and associated with higher procedural risk

Figure 5

Right internal carotid artery injection demonstrating a severe stenosis associated with a loop in the distal ICA

Figure 6

Native image of RICA injection in lateral projection. The loop in the distal ICA makes placement of the EPD technically more challenging and associated with greater procedural risk

Figure 7

RICA injection in lateral projection post successful CAS with minimal residual stenosis and good TICI III flow without EPD-induced spasm or dissection

Figure 8

Flow chart defining the carotid board process of patient selection for carotid artery stenting

Carotid stenting technique

The CAS procedures were performed in standard fashion, as previously described in the literature, by three credentialed operators (MK, WS, HM) who were approved by the MDCB and appropriate institutional committees.[ 3 10 19 ]

Clinical outcomes

Follow-up information was obtained on each patient from post-procedure clinical evaluation and our electronic medical records. The following clinical outcomes were evaluated: any stroke, myocardial infarction, or death within 30 days of the procedure.

Stroke was defined as any hemorrhagic or ischemic event associated with a neurological deficit lasting longer than 24 hours. Strokes were classified as major or minor on the basis of the National Institutes of Health Stroke Scale, and the modified Rankin scale (mRS).[ 5 15 ] Myocardial infarctions were classified as Q-wave (new pathological Q waves in two or more contiguous electrocardiographic leads) or non–Q-wave (with elevation of the troponin level).[ 10 ] Other procedure-related complications were documented, such as transient ischemic attacks (TIA), access complications, need for transfusion and vessel injury. Periprocedural hemodynamic instability was recorded and defined as a drop in systolic blood pressure or heart rate requiring an increase in the acuity of care or need for pressors greater than 12 hours.

After 30 days, death was classified as death from neurological event or other cause. Stroke was defined as in the territory of the ipsilateral treated vessel, or non-target, unrelated to treated vessel. Follow-up imaging was performed to assess for restenosis. Target-vessel revascularization was defined as repeat percutaneous or surgical treatment of the previously stented carotid artery.

RESULTS

Seventy-four CAS procedures were performed in 69 patients. No patients underwent CAS without MDCB approval at our institution. Five patients underwent two separate procedures for bilateral disease as recommended by the MDCB. Some patients met the criteria for more than one high-risk category. The basic variables are shown in Table 1 .

All patients underwent digital subtraction angiography (DSA) prior to the stenting procedure. Angiographic features associated with increased procedural risk were demonstrated in 37/69 (54%) patients, as follows: significant plaque ulceration (n = 11), heavy plaque calcification (n = 7), difficult to catheterize aortic arch (n = 9), and difficult to navigate lesions or tortuous cervical internal carotid arteries (n = 10)[ 10 ] [Figures 1 – 7 ]. Embolic protection devices (EPDs) were successfully utilized in 95% (70/74) of the procedures. Four cases were performed without EPD for technical reasons. Buddy wires were used in 5.4% of the procedures (4/74) to assist in placement of the EPD. Two (2.7%) patients underwent angioplasty alone without stenting. Four (5.4%) patients had placement of 2 stents in an overlapping fashion.

The immediate post-treatment angiographic result ranged from 0 to 49% stenosis, with median residual stenosis of 12.5%.

The 30-day periprocedural major adverse event (MAE) rate for the 69 patients who underwent 74 CAS procedures included two (2.7%) deaths. [ Table 2 ] Both patients died after uneventful procedures and subsequent hospitalizations. They were discharged from the hospital and presumably died from non-neurologic or non-procedure-related complications. One symptomatic patient with stage IV poorly differentiated endometrial adenocarcinoma died of sepsis secondary to chemotherapy related neutropenia. The exact cause of death in the other patient who was 87-year-old and died 18 days after her procedure is unknown. Both of these patients were symptomatic and the decision to treat was performed in a multidisciplinary fashion with the patient's family. Despite other severe medical comorbidities they were expected to have a long-term survival.

Table 2

30-day Morbidity and Mortality

Other periprocedural MAEs included: 4 strokes (5.4%, 2 minor and 2 major), 2 myocardial infarctions (2.7%), 1 Q-wave MI with a peak troponin 10.82, 1 non-Q wave MI with a peak troponin 0.55, 3 TIAs with full neurological recovery within 24 hours and no diffusion-weighted abnormalities on MRI (4%), two minor upper gastrointestinal bleeds presumably related to antiplatelet medications (2.7%), and 11 instances of significant sustained hemodynamic instability after stimulation of the carotid baroreceptor (14.9%). Two periprocedural myocardial infarctions, one stroke, and one TIA were associated with sustained hemodynamic instability. Recurrent stenosis of over 50% was identified in 8 patients with mean follow-up of 21 months. Two were symptomatic and six were asymptomatic. Target vessel revascularization procedures were performed in 2/69 (2.9%) patients; one was repeat CAS and one CEA.

Significant events between 30-365 days included: ipsilateral stroke in the territory of the stented carotid artery (n = 2), stroke in non-target vascular territories (n = 2), and death from non-neurological causes (n = 4). At one year, including the periprocedural MAE, 14.5% of patients reached primary endpoints (i.e. 4 periprocedural stroke, 2 periprocedural death, 2 periprocedural MIs, and 2 ipsilateral stroke). Analysis of all death (i.e. periprocedural, neurologically related or non-neurologically related) and stroke events (i.e. periprocedural, target and non-target stroke) in this high-risk cohort during the first year revealed that 14 (20.3%) patients experienced an adverse event (stroke [n = 8], death [n = 6]).

Follow-up beyond 1 year to a mean follow-up of 21 months revealed two more non-target vessel related strokes and an additional 7 non-neurological cause related deaths. Therefore, in this high surgical risk patient cohort that underwent CAS with EPD, 13/69 (18.8%) patients died and 10/69 (14.5%) patients experienced a stroke within a mean follow-up period of 21 months. The mean mRS at 21 months was 2.2.

There was no significant difference in the cumulative incidence of MAE for symptomatic, medical high-risk, age ≥80 year, CMS criteria,[ 7 18 ] degree of stenosis, anatomical high risk and hemodynamic events; however, the difference in the cumulative incidence of MAE between patients with and without angiographic features associated with increased procedural risk was significant (P=0.047) [ Table 3 ].

Table 3

One-year cumulative incidence of all major adverse events (periprocedural stroke, target vessel/nontarget vessel stroke, all death, and MI)

DISCUSSION

The Centers for Medicare and Medicaid Services (CMS) guidelines support protected CAS for patients at high risk for surgery with symptomatic carotid stenosis ≥70%.[ 7 18 ]

However, the clinician is often confronted with high surgical risk patients in need of carotid revascularization who do not fit these guidelines. In these cases, the MDCB proved useful in adjudicating the appropriate revascularization strategy. It provided an accumulated experience with fundamental medical and surgical skills in vascular surgery, interventional neuroradiology, cardiology, neurology and neurosurgery for instances in which high-level evidence was lacking or not directly applicable to a given patient. The MDCB also helped facilitate the conscientious, explicit and judicious use of current best evidence in making decisions about the care of individual patients. It provided and enforced institutional standards regarding CAS indications, technical performance and credentialing at our institution. The MDCB mandated that all CAS procedures and referrals be presented before the board for approval. This collaborative effort also circumvented the traditional turf battles that can occur between the various subspecialty groups treating carotid stenosis. The board helped clarify the patient problem being addressed. It identified the important variables and evidence critical to best treatment and monitored the clinical outcomes specific to our institution.

The formation of the MDCB was a daunting task and not without some resistance. Initially, the physicians had no incentives to change from their traditional methods of functioning. Nor were they inclined to transfer the administration of their clinical recommendations to a central authority such as the MDCB. The successful formation of the board can be attributed to the strong mandate from the institution and the willingness of the individual subspecialties to relinquish exclusive claims to surgical and endovascular techniques, authority and specialist knowledge.

The treatment of carotid stenosis intersects the traditional subspecialty paradigms. With the advent of CAS, new groups of physicians are now treating carotid stenosis. The distribution of interventionalists by medical specialty who participated in the CREST Trial were 40% cardiologists, 23% interventional neuroradiologists, 16% vascular surgeons, 11% interventional radiologists, 7% neurosurgeons and 3% neurologists.[ 14 ] Each subspecialty group has its strengths, weaknesses and inherent biases. This was quite apparent in our initial MDCB conferences. Simple concepts such as degree of stenosis, interpretations of the diagnostic imaging, and clinical determinations were debated. The subspecialty silo effect made communication of the basic variables sometimes ambiguous leading to additional diagnostic testing, uneven quality and increasing costs. As the operational reciprocity improved, the MDCB was able to establish universal institutional guidelines for CAS. It improved interdepartmental communication, collaboration and referrals. Similar to the goals of healthcare reform, the MDCB served as an integrated delivery system that provided organizing connections among disparate parts of the health system and, in so doing, theoretically created efficiencies and reduced redundancies resulting in improved patient care and cost controls.[ 22 ]

The patients referred for CAS in this prospective case series represented a highly selected and rigorously reviewed group of patients. Low-to-moderate surgical risk patients were not reviewed by the MDCB nor referred for CAS at our center. During this time period, 3682 patients with stroke and 812 patients with TIA were admitted and treated at our center, and of these 343 carotid endarterectomies (CEA) were performed. CAS represented only 16.8 % of all carotid revascularization procedures performed at our academic institution. This highlights the fact that formation of MDCB at our institution kept the CAS numbers to a necessary minimum.

Our results compare favorably to the literature.[ 3 4 7 9 – 12 14 – 18 24 ] The composite 1-year MAE of 14.5% is slighter higher than the 12.2% reported in SAPPHIRE.[ 24 ] This difference may be partly accounted for by the greater number of octogenarians and symptomatic high surgical risk patients in our patient cohort. In addition 37/69 patients were found to have angiographic features associated with increased procedural risk such as tortuous anatomy, heavy calcification and ominous plaque morphology[ 10 ] [Figures 1 – 7 ]. These well-known angiographic high-risk variables played a significant role in the safe performance of CAS and directly impacted the periprocedural complication rate (i.e. MAE). The difference in cumulative incidence of MAE between patients with and without angiographic features associated with increased procedural risk was statistically significant (P = 0.047).

All the patients included in this cohort were considered high risk for surgery. Many were greater than 80-year-old, had medical comorbidities such as advanced cancer, HIV, atrial fibrillation with congestive heart failure, and unstable neurological conditions with recent strokes. All of these patients would have been excluded from the landmark low-risk randomized controlled trials, such as ACAS, ACST, NASCET, SPACE, EVA 3s, CREST and many would have been excluded from SAPPHIRE as well.[ 1 2 4 8 10 16 20 23 ] Our patient profile may not even represent a fair comparison to SAPPHIRE or other high-risk registries.[ 1 9 21 ] This patient profile more closely parallels the current clinical reality in regard to high-risk surgical patients treated outside randomized controlled trials at tertiary centers. Of the patients enrolled in SAPPHIRE, 71% were asymptomatic, as were 86.2% in the Carotid RX ACCULINK/ACCUNET Post-Approval Trial to Uncover Unanticipated or Rare Events CAPTURE compared to only 39% in our study.[ 9 21 24 ] In SAPPHIRE 19.5% (65/334) were 80 years old or older.[ 24 ] In SAPPHIRE, age >80 alone qualified the patient as high surgical risk.[ 24 ] In our study 26% were octogenarians; however, age >80 alone was not sufficient to merit high surgical risk status. Therefore, it is to be noted that the patients enrolled in SAPPHIRE were not truly high risk and the outcomes would have been much worse if patients from our cohort were a part of the SAPPHIRE study.

Our nonperiprocedural ipsilateral stroke rate was 2.9% with mean follow-up of 21 months. The stent arm of SAPPHIRE reported 2.4% (4/167) ipsilateral stroke rate between 1 and 3 years.[ 21 ] Target vessel repeat revascularization was required in 2.9% of our patients at mean follow-up of 21 months compared to 2.8% of patients at 2-year follow-up in the ARCHeR LTFU Trial.[ 9 ] The overall mortality rate with a mean follow-up of 21 months in our study of 18.8% (13/69) compares favorably to the results reported in the stenting arm of SAPPHIRE at 36 months (18.5%), 31/167.

There are limitations to our study. This represents information from a prospective registry of high surgical risk patients who underwent CAS. Therefore, we do have a prospective control group neither of patients treated medically nor surgically for comparison. Moreover, since the MDCB was created in direct response to the Food and Drug Administration (FDA) approval for the use of CAS with protection device in certain patients at high surgical risk for CEA, we do not have a comparative population who underwent carotid stenting with EPD before the MDCB was formed.

Lessons learned

Multidisciplinary approach does not necessarily equate to better outcomes, increased volume, or specialty growth. However, it does provide a quality control element, diminishes the silo effect, eliminates turf battles and interobserver variation, levels the playing field, facilitates an evidence-based approach and improves collaboration and consensus in this evolving field. The evidence available to the MDCB is not well-established but it was the only source of reference to our team. This paper is not a guideline paper. It just demonstrates that a MDCB is feasible and here are some of the salient lessons learned.

Although most deaths were due to non-neurological causes, the mortality rate in this high surgical risk cohort is not insignificant. Generally the natural history of high-risk surgical patients especially the asymptomatic high-risk surgical patients is not well known. Therefore from our local experience, we cannot justify the routine treatment of asymptomatic high-risk surgical patients with severe carotid stenosis. The benefit of CAS for asymptomatic high-risk surgical patients is only marginal and is rapidly lost because of the increased rate of procedural complications, advanced age, and severe medical comorbidities limiting long-term survival. We feel that our MDCB overestimated the life expectancy in some of these patients. In addition, the MDCB under estimated the clinical relevance of angiographic high risk features. It is also felt that the MDCB did not realize the full potential of maximal medical management and frequently was too aggressive in recommending CAS in these high-risk surgical patients. Through this MDCB, there is possibility of different specialties to collaborate on the same case, scrub with each other in the intervention suite or the operating theater to learn the best techniques from each other in order to apply to their patients for better outcomes. These are learning points for not only our group but also other institutions who are interested in establishing a MDCB of their own. We believe that such reported experience from our institution will not only help us improve outcomes in future but others as well. It is difficult but not impossible to implement such a model in solo practice. Adherence to guidelines, constant reappraisal of results and unbiased inference of the clinical trials are important. A critical analysis of published stenting trials in provided in Table 4 . Moreover, maximal medical management should always be considered an option.

Table 4

Critical analysis of stenting trials

CONCLUSIONS

While CAS evolves into an acceptable treatment option for both low and high surgical risk patients at experienced centers, the current clinical reality calls for increased multidisciplinary collaboration between clinicians, surgeons, proceduralists and non-proceduralists. The overall long-term morbidity and mortality in the treatment of high surgical risk patients with CAS is not trivial. This study demonstrates a successful multidisciplinary model for the treatment of high surgical risk patients with CAS. The goals of this group were to ensure the appropriateness of CAS referral and establish and maintain high standards for the individuals performing CAS procedures. Multidisciplinary review and ongoing audits of results should be performed at all centers offering CAS. We found the MDCB to be extremely helpful in fostering the physician stewardship of healthcare at the practice level. This publication can serve as a template for the development of such collaborative teams.

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