The Institute for Advanced Medical Education is accredited by the Accreditation Council for Continuing Medical Education (ACCME) to provide continuing medical education for physicians.

The Institute for Advanced Medical Education designates this educational activity for a maximum of 2 AMA PRA Category 1 Credit(s) TM. Physicians should only claim credit commensurate with the extent of their participation in the activity.

These credits are accepted by the American Registry for Diagnostic Medical Sonography (ARDMS).

Faculty:
Brad L. Johnson, MD
Associate Professor of Surgery
University of South Florida
Division of Vascular and Endovascular Surgery
Tampa, Florida

Course: The Treatment of Carotid Disease- Carotid Endarterectomy vs. Carotid Artery Stenting

Target Audience: Physicians who treat carotid artery disease.

System requirements: In order to complete this program you must have a computer with a recent version of Internet Explorer or Netscape, and a printer, which is configured to print from the browser.

For any questions or problems concerning this program or for problems related to the printing of the certificate please contact IAME at (914) 921-5700 or email us.

Estimated Time for Completion of tutorial: Two hours
Date of Release and Review: January 9 , 2007
Expiration Date: January 9, 2010

Disclosure: In compliance with the Essentials and Standards of the ACCME, the author of this CME tutorial is required to disclose any significant financial or other relationships they may have with the manufacturer(s) of any commercial product(s) or provider(s) of any commercial service(s) discussed in this program.

Dr. Brad Johnson does not have any financial or other relationships to disclose.

IAME discloses no relevant financial relationships with commercial interests. 

IAME Statement on Privacy and Confidentiality

The Treatment of Carotid Disease- Carotid Endarterectomy vs. Carotid Artery Stenting
Brad L. Johnson, MD
Associate Professor of Surgery
University of South Florida
Division of Vascular and Endovascular Surgery
Tampa, Florida

(DIRECT TO QUIZ)

Objectives
After completing this course, the participant should be able to:

• Understand carotid artery disease and its relationship to stroke
• Understand indications for carotid artery disease interventions
• Understand the risks of carotid endarterectomy vs. carotid artery stenting
• Have a general concept of which patients should have either of the above procedures

Introduction

The primary reason to treat carotid artery disease is lower the incidence of stroke. Stroke is a major health problem in the United States with approximately 500,000 people suffering a first stroke each year. While two fifths will die from it, the rest suffer significant disabilities that cause personal and economic hardships.

Since treatment after a stroke is not optimal the primary focus should be prevention. Since C. Miller Fisher first published an article in 1951 we now understand that carotid embolus or less likely occlusion due to internal artery atherosclerotic plaque build-up cause the majority of strokes. In a 373 postmortem examinations of the brains of stroke victims, he found less than 20% died from cerebral hemorrhage, whereas the majority had atherosclerotic disease of the proximal internal carotid artery and no significant intracranial artery disease.

		The ultimate goal of carotid intervention is to identify clinically significant disease, so that treatment can be applied and risk of stroke reduced.
Figure 1 - Plaque in a carotid artery prior to endarterectomy. To view an enlargement, click on the image.

With the first successful carotid endarterectomy performed by DeBakey in 1953 and first published case report by Eastcott, Pickering, and Rob in 19542, the era of surgical treatment for symptomatic extracranial carotid disease began. These pioneering operations resulted in immediate acceptance of carotid endarterectomy for stroke prevention by surgeons who then evolved CEA to a signature procedure of vascular surgery. The first randomized clinical trial for symptomatic patients was published in 1970 and emphasized that while carotid endarterectomy provided protection from future ipsilateral stroke, the beneficial effects could be negated if associated with a high (>10%) procedural complications (stroke, death)3. One noteworthy community-based study performed by neurologists reported perioperative stroke/death rates in the range of 20% leading to a subsequent controversy over the safety and long-term efficacy of CEA4. Despite these concerns in the medical community, the number of carotid procedures for cerebral ischemic syndromes (hemispheric stroke, reversible ischemic neurologic defect [RIND], transient ischemic attack [TIA], amaurosis fugax, vertebrobasilar insufficiency), and asymptomatic carotid stenosis gradually increased until in the 1980s more than 100,000 procedures were performed annually in the United States, 2nd only to coronary artery bypass grafting in total numbers. The number of carotid endarterectomies done in Medicare recipients reached a high of 144,000 in 1997 with regional rates ranging from 1 to 7.5 per thousand Medicare enrollees. The efficacy of these expanded indications for CEA were again questioned by the neurology community who also cited that improvements in medical therapy by antiplatelet therapy, control of hypertension, and atherosclerotic risk factor reduction might reduce the need for invasive intervention.

Figure 2 To view an enlargement, click on the image.

Results of the NIH sponsored clinical trials (NASCET, ACAS) now provide the basis for carotid intervention5,6. In both of these prospective, randomized, multicenter clinical trials stroke prevention was documented after CEA based on patient selection criteria that included a specific angiographic-confirmed severity of carotid stenosis, and completing the procedure with a low (less than 5%) perioperative combined stroke/death rate. For symptomatic patients with 50% or greater stenosis of the ICA, the NASCET trial demonstrated medical therapy was less effective compared to surgery for >70% stenosis with relative risk reductions of 57% at 1-year and 67% at 2-years5. When the stenosis was <60% DR, the risk of stroke in the medically treated group was 8% after 5 years, but doubled to 16% over the same period when stenosis severity increased to 60-99%. Based on NASCET results, only six uncomplicated CEAs need to be performed to prevent one stroke. Benefit of CEA was also demonstrated in other clinical trials of symptomatic patients with stroke/death reductions of 39% (European Carotid Trial, ECAS) and 60% (Veterans Affairs Cooperative Trial)7,8. Clinical trials (ACAS, Veterans Affairs Cooperative Trial) conducted on asymptomatic patients with 50-60% diameter reduction ICA stenosis have also demonstrated reduction (relative risk reduction of 30% and 53%) of ipsilateral stroke and death due to stroke after CEA compared with "best" medical treatment6,9. Based the ACAS data, 17 patients need to be subjected to surgical intervention to prevent one stroke by 5 years. Some controversy has existed due to the use of carotid angiography in the ACAS trial and not duplex scanning as the screening exam. The method of measurement for the degree of 60% stenosis by angiography actually correlates with a 75-85% stenosis by duplex scanning. Therefore most vascular surgeons only recommend CEA in asymptomatic patients with a greater than 75-80% stenosis by duplex scanning. Furthermore because the ACAS trial did not demonstrate a benefit from CEA until three years after surgery, the risk/benefit ration of performing CEA among individuals with high-risk comorbid conditions needs to determine on a patient-patient basis. Patients greater than 75-80% stenosis that that are likely to die of another cause other than stroke within 3 years of their diagnosis should probably not undergo CEA.

Figure 3 - Carotid artery duplex scan showing a >80% stenosis of the carotid artery with the distal normal making this patient a good candidate for CEA. To view an enlargement, click on the image.

Stroke associated with CEA has been reported in 1-12% of patients varying with indication for intervention and the institution where the procedures were performed. Observations from the Ontario Carotid Endarterectomy Registry (6038 patients) found a history of TIA, stroke, contralateral occlusion, diabetes, atrial fibrillation and congestive heart failure are independent predictors for increased risk for stroke or death at 30-days after carotid endarterectomy10. In the large randomized clinical trials (NASCET, ACAS), the procedural disabling stroke rate was less than 2%. Carotid endarterectomy has also proven to be a durable procedure for stroke prevention with late occlusion rate of less than 2%, re-intervention rate of <5%, and ipsilateral hemispheric stroke risk of approximately 5% at 5-years. More recent single-institution audits (1000 patients) of carotid endarterectomy reported perioperative mortality rate of 0.3%, stroke rate of 0.9% and a late incidence of late occlusion and recurrent >70% stenosis rates of 0.6% and 0.5% respectively11.

Figure 4 - Algorithm for management of asymptomatic carotid disease. To view an enlargement, click on the image.

Figure 5 - Algorithm for management of symptomatic carotid disease. To view an enlargement, click on the image.

The introduction of stent-assisted carotid angioplasty (CAS) has re-ignited the debate on application of CEA for patients with serve carotid bifurcation occlusive disease. At institutions performing CAS under an investigational protocol, the technical success has exceeded 97% and procedural neurologic morbidity has decreased progressively with experience from initial stroke rates of 7-10% to now less than 5. Initial stroke rates of 7-10% were thought to be from less experienced interventionlists, inferior medical equipment used in the procedure, and lack of an embolic protection device. Recent trials using a embolic protection device such as the Stenting and Angioplasty with Protection in Patients at High Risk for Endarterectomy (SAPPHIRE) have had only a 3.6% 30-day incidence of stroke after stenting12. While some vascular surgeons criticized the study for its high stroke and death rate for the CEA patients it did show that CAS could be done safely. More recently the publication of the Endartectomy versus Stenting in patients with Symptomatic Severe Carotid Stenosis in the New England Journal of Medicine has further confused the picture15. The study was stopped early for reasons of safety. The 30-day risk of any stroke or death was significantly higher after CAS (9.6%) than after CEA (3.9%). Hopefully the CREST trial currently underway in which patients are being randomized to CAS or CEA in both symptomatic and asymptomatic patients who are not at high risk for surgery will provide an answer.

The Procedures

Carotid Endarterectomy

Up to 95% of CEAs are based on the finding of duplex scanning without the need for carotid angiography.  Patients in which the duplex scan is not adequately able to visualize the carotid disease (ie. severe calcification), demonstrates evidence of proximal brachiocephalic disease, or the internal carotid disease extends distally to the base of the skull need to undergo and additional study such angiography, MRA, or CT angiogram. The procedure is performed under general anesthesia or cervical block. Debate still continues on whether or not to shunt all patients or monitor with EEG in those patients that undergo a general anesthestic.

Figure 6 - A shunt is in the carrying blood from the common carotid artery to the distal internal carotid artery while a CEA is performed. To view an enlargement, click on the image.

Also while not all surgeons place a carotid artery patch that has been some literature to suggests it likely reduces the incidence of stroke and recurrent carotid artery stenosis. Most patients are discharged the day after surgery and have a limited recovery time. Complications include cranial nerve injury, postoperative variations in blood pressure, Neck hematoma requiring return to operating room, and rarely cerebral hyperperfusion syndrome. The incidence of cranial nerve injuries in a prospective study by Hertzer and colleagues found an incidence of 16% with only 60% symptomatic. Most are temporary with only 1-4% still symptomatic 6 weeks postoperatively. Hypertension and hypotension have an incidence of 19% and 28% respectively in patients undergoing CEA. While it can easily be treated failure to treat promptly can increase the incidence of neurologic deficits. Cerebral hyperperfusion syndrome occurs in less than one percent yet can be fatal if not recognize. This occurs in patients who have a history of systemic hypertension and severe chronic cerebral ischemia due to bilateral ICA stenosis of greater than 95%, a high grade carotid stenosis with contralateral occlusion, and unilateral high grade stenosis with poor collateral coss-filling of that hemisphere. Patients complain of a severe unilateral headache, followed byipsilateral cerebral neurologic deficit and/or seizures. Head CT can be normal or show cerebral edema. Patients that complain of a severe unilateral headache should have good systemic blood pressure control and be treated with anticonvulsants.

Carotid Artery Stenting

Similar to CEA must patients have a carotid duplex scan as their initial study yet they usually require another study (cerebral angiography, MRA, or CT angio) prior to placement of the stent.  Initially most patients underwent a diagnostic angiography to determine if they were a candidate and also to measure the size of the stent to be used, then another angiogram to place the stent.  Some interventionallists have now started using CT angio to avoid having two invasive procedures.  Relative anatomical contraindications to placing a carotid stent include severe angulation of the great vessels origins from the aortic arch, severe tortuosity of the common or internal carotid artery, severe calcification of the aortic arch, or severe calcification of a tight carotid stenosis.  Inability to access from a femoral artery approach due to aortic or iliac disease usually prevents carotid stenting even though the brachial artery or proximal common carotid access has been used.  Free floating thrombus in the carotid artery is an absolute contraindication to stenting while some consider soft echolucent carotid plaque to be a relative contraindication.

The steps of the procedure consist of obtaining access via the common femoral artery.  If a prior study of the aortic arch has not been obtained then a 5 French pigtail catheter is inserted through a 5 French femoral sheath. 

Figure 7 - Diagram showing a catheter from the right common femoral artery into the distal internal carotid artery. To view an enlargement, click on the image.

An aortic arch angiogram is then obtained in a 20-to 45-degree left anterior oblique orientation to open up the artic arch adequately. The type of catheter used to select the common carotid artery(CCA) will depend on the type of arch( see figure of type of arches).  After selected out the CCA there are different techniques for proceeding with placement of the stent.  One used often is to obtain a agiogram with roadmapping then pass a stiff glidewire into the ECA.  A guiding catheter is placed over the wire into the CCA followed by a 6 or 7 French shuttle sheath  pleaced into the CCA over this.  The catheter and guidewire are then removed and a closed protection device(CPD) using a monorail system placed through the ICA stenosis.  While some interventionallists will pre-dilate all lesions I tend to do this in only tight lesions.  Again using a monorail system the stent is then placed.

Figure 8 - A carotid artery stent with the distal embolic protection device in place. To view an enlargement, click on the image.

Residual stenosis of 10 to 20% is acceptable otherwise postdilatation is performed with balloons typically 5 to 5.5mm in diameter.  Most patients during postdilatation will become bradycardic secondary to stimulation of the carotid sinus baroreceptors. This usually easily treated with atropine while some use volume expansion before dilatation of the stent.  The CPD is then retrieved through a catheter that collapses it back inside.  Completion carotid and cerebral angiograms are then obtained.  I obtain a carotid duplex scan in the recovery room to assure of no technical error and to have a baseline study.  Most patients are discharged on the following day.  Complication consist of thrombosis at the stent site, embolization, labile blood pressure, or rarely cerebral hyperperfusion syndrome.  Postoperatively in-stent stenosis occurs in approximately 5% of patients and treated successfully with balloon angioplasty.  Rarely does it require open surgery.

To view an enlargement, click on the image.

Discussion

Primary care physicians must be informed of the wide range of operative stroke/death rates that exist among interventionists and high procedural morbidity adversely influences long-term benefit especially in the asymptomatic patient.  Recent statewide and Medicare audits suggest the operative results of CEA may be inferior in community hospitals at which most operations are actually performed as compared to surgical results at academic or large referral centers.  Surgical risk also varies from one hospital to another and with each surgeon.  Favorable outcomes appear to be inversely related to the volume of procedures performed.  Hospital volumes of less than 40 procedures per year and surgeon volumes less than 4 per year were associated with increase complications (stroke, death).  Best outcomes after CEA were achieved by board-certified vascular surgeons.  The low complications associated with CEA in the NASCET and ACAS trials were the results of experienced surgeons practicing in specialized vascular units.  It is the responsibility of individual institutions and their medical staff to perform outcome surveillance following CEA and CAS.12  If a prospective audit indicates a 30-day postoperative stroke and mortality rate exceeding 5-7%, a review of procedure indications, technique(s), and patient monitoring should be initiated.   The Leapfrog Group, an advocate for standards for evidence-based hospital referrals, suggests a minimum institution procedure volume of 100 per year.

The designation of CEA as the "gold standard" for the treatment of severe (>50% diameter reduction) carotid stenosis required four decades of experience and refinement of the both the procedure and its indications.  Contemporary practice guidelines have been developed by a number of professional societies.  Patients are deemed surgical candidates based on an arterial evaluation demonstrating severe carotid stenosis and a medical evaluation indicating absence of severe coronary artery occlusive disease.  In either symptomatic or asymptomatic patients, a threshold stenosis severity of greater than 60% diameter reduction demonstrated by duplex ultrasonography, and/or angiography (contrast, magnetic resonance) should prompt a vascular consultation and consideration for intervention or enrollment in a program of stoke prevention with surveillance for disease progression and control of atherosclerotic risk factors.  A multidisciplinary consensus statement from an ad hoc committee of the American Heart Association summarized the guidelines for carotid endarterectomy into three categories: proven, acceptable, but not proven, and uncertain.13

In patients who are at increased risk for complications from CEA or anticoagulation, CAS may be considered an alternative if a skilled and experienced interventionalist is available.  Patients who may be considered for CAS include:

• high carotid lesions not surgically accessible
• restenosis after carotid endarterectomy
• radiation induced carotid stenosis
• serious medical co-morbidity

In center of CAS excellence, the procedure has technical success, complication, and patency rate comparable to surgical results including those of the NASCET trial. The Acculink stent and Accunet embolic protection device (Guidant Corporation) along with the Xact stent and Emboshield embolic protection device (Abbott Corporation)  are only only carotid stent systems approved by the FDA .  They are only approved for patients who meet the above criteria or who entered into a FDA approved study. The Acculink stent is an open cell design while the Xact stent is a closed cell which theoretically may be better for soft friable carotid plaque that could protrude through a open cell stent.  Another issue of concern is the role of carotid stenting in the octogenarian.  Results from the Carotid Acculink Postapproval Trial to Uncover Rare Events (CAPTURE) showed a stroke, rate of death, or myocardial infarction during the first 30 days after carotid stenting of 4.3% in patients younger than 80 years and 7.7% in patients older than 80 years. Therefore there are still many unanswered question concerning carotid artery stenting that hopefully be resolved with future randomized trials.  The Carotid Revascularization Endarterectomy versus Stent Trial (CREST) is a randomized study uner way that hopefully will answer many of these questions. For the CREST  anatomic criteria for inclusion in the randomization portion of the study include:

• Stenosis >50% DR by angiography
• Stenosis >70% DR by duplex ultrasonography. 

Initially only symptomatic patients were being enrolled yet now asymptomatic patients are included which allow the study to be completed soon.

References

1. Fisher M. Occlusion of the internal carotid artery. AMA Arch Neurol Psychiat 1951;65:346-377. 

2. Eastcott HHG, Pickering GW, Rob CG. Reconstruction of internal carotid artery in a patient with intermittent attacks of hemiplegia. Lancet 1954;2:994-6. 
3. Fields WS, Maslenikov V, Meyer JS, et al. Joint Study of extracranial arterial occlusion: V. Progress report of prognosis following surgery for transient ischemic attacks and cervical carotid lesions. JAMA 1970;8:1993-2003.
4. Easton JD, Sherman DG. Stroke and mortality in carotid endarterectomy: 228 consecutive operations. Stroke 1977;8:565-8. 
5. 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;325:445-63. 
6. Executive Committee for the Asymptomatic Carotid Atherosclerosis Study: Endarterectomy for asymptomatic carotid stenosis. JAMA 1995;273:1421-28. 
7. European Carotid Surgery Trialists’ Collaborative Group: MRC European Carotid Surgery Trial. Interim results for symptomatic patients with severe (70-99%) or with mild (0-29%) stenosis. Lancet 1991;337:1235-1243. 
8. Mayberg MR, Wilson SE, Yatsu R, et al. Carotid endarterectomy and prevention of cerebral ischemia in symptomatic carotid stenosis. JAMA 1991;266:3289-3294. 
9. Hobson RW, Weiss DG, Field WS, et al and the Veterans Affairs Cooperative Study Group. Efficacy of carotid endarterectomy for asymptomatic carotid stenosis. N Engl J Med 1993;328:221-7. 
10. Tu JV, Wang H, Bowyer B, et al. Risk factors for death or stroke after carotid endarterectomy: Observations from the Ontario Carotid Endarterectomy Registry. Stroke 2003;34:2568-75.
11. Ballotta E, Da Giau G, Piccoli A, Baracchini C. Durability of carotid endarterectomy for treatment of symptomatic and asymptomatic stenosis. J Vasc Surg 2004;40:270-8.
12. Hertzer NR. Presidential address: Outcome assessment in vascular surgery – Results mean everything. J Vasc Surg 1995;21:6-15.
13. Guidelines for Carotid Endarterectomy: a multidisciplinary consensus statement from the ad hoc committee, American Heart Association. Circulation 1995;91:566-79.
14. Mas JL, Chatellier G, Beyssen B. et al. Endarterectomy versus Stenting in Patients with Symptomatic Severe Carotid Stenosis. N Engl J Med 2006;355:1660-71

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