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Symptomatic Carotid Artery Stenosis Bradley N. Bohnstedt, MD1
Ryan Dhaemers, MD2
1 Department of Neurological Surgery, Indiana University School of
Medicine, Indianapolis, Indiana 2 Department of Radiology, Indiana University School of Medicine, Indianapolis, Indiana 3 Goodman Campbell Brain and Spine, Indianapolis, Indiana
Daniel Hsu, MD3 Address for correspondence Bradley N. Bohnstedt, MD, Department of Neurological Surgery, Indiana University School of Medicine, 355 W 16th Street, Suite 5100, Indianapolis, IN 46202 (e-mail: [email protected]).
Abstract
The management of patients with extracranial carotid artery stenosis remains controversial. Randomized controlled studies established the value of carotid endarterectomy (CEA) over optimal medical therapy for patients with symptomatic carotid stenosis. For patients with carotid stenosis, optimal medical therapy includes antiplatelet agents, antihypertensives, and lipid-lowering medications along with lifestyle modifications. Some studies and experts have challenged these treatment methods and consider carotid artery stenting with distal protection as an alternative to CEA. In this article, the authors review current guidelines and supporting studies and suggest practical approaches to this common clinical problem.
Keywords
► carotid stenosis ► carotid endarterectomy ► carotid artery stenting
Carotid disease is responsible for 10 to 20% of ischemic strokes.1 Symptomatic disease refers to signs or symptoms referable to the diseased carotid artery. The last few decades have witnessed a revolution in the diagnosis and treatment of carotid disease. In this article, we will review the diagnostic studies, therapeutic options, and outcomes of symptomatic carotid artery disease.
Diagnostic Studies Diagnosis Imaging evaluation for carotid disease was first performed with conventional catheter angiography,2 and later improved to digital subtraction arteriography (DSA).3 Digital subtraction arteriography remains the gold standard; it is an invasive procedure, however, that carries a 1 to 3% complication risk.4–6 As early as 1975, noninvasive methods were developed to evaluate carotid artery stenosis.7,8 Carotid Doppler ultrasound has a sensitivity of 72 to 96% and a specificity of 61 to 100% for high-grade stenosis.9 However, its use is limited in the setting of calcification and may overestimate stenosis.10,11 The initial use of noncontrast-enhanced computed tomography (CT) of the neck was for detection of calcifications of the carotid artery in patients with transient ischemic attacks (TIAs).12 With the development of CT angiography (CTA), high-quality
Issue Theme Advanced Cerebrovascular Disease Management; Guest Editor, Jason Mackey, MD, MS
noninvasive arterial imaging became possible (►Table 1).13 Advances in magnetic resonance angiography (MRA) have allowed additional noninvasive imaging without ionizing radiation or iodinated contrast (►Table 1).14–16 When patients present with symptoms of amaurosis fugax, TIA, or stroke, the initial evaluation should include carotid Doppler.17 If > 70% stenosis is found, intervention may be justified. In symptomatic patients for whom sonography results are equivocal or nondiagnostic, CTA or MRA are indicated.17 If doubt remains in the diagnosis, DSA of the carotid should be considered. For the symptomatic patient with >50% stenosis by DSA or >70% by noninvasive imaging, the current recommendation is for intervention.18,19
Optimal Medical Therapy Optimal medical therapy for carotid artery stenosis is focused on treatment and reduction of both risk factors and thrombotic risk. Risk factor reduction includes behavioral modifications such as smoking cessation,20 exercise, and weight control.21 Tight control of hypertension (goal < 140/90),22 diabetes (hemoglobin A1c level < 6.5%),23 and hypercholesterolemia (< 100 mg/dL) further reduces risk.17 In patients with symptomatic carotid stenosis, antiplatelet agents such as daily aspirin (75–325 mg), clopidogrel (75 mg), or aspirin plus extended-release dipyridamole (25/200 mg
Copyright © 2013 by Thieme Medical Publishers, Inc., 333 Seventh Avenue, New York, NY 10001, USA. Tel: +1(212) 584-4662.
DOI http://dx.doi.org/ 10.1055/s-0033-1364218. ISSN 0271-8235.
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Semin Neurol 2013;33:456–461.
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Table 1 Recommended diagnostic tests for suspected carotid stenosis Test
% Stenosis Indicating Treatment
Sensitivity (%)
Specificity (%)
References
100
100
Celesia et al3
72–96
61–100
Duncan et al7 Suwanwela et al9 Weaver et al10
70–99
46–84
39–97
Chappell et al15 Petrou et al16
50–69
20–90
63–92
Chappell et al15 Petrou et al16
DSAþ Symptomatic patients
50
Carotid Doppler
Symptomatic
70
Symptomatic
Masaryk et al48
CE-MRA Symptomatic
70–99
69–97
76–96
Chappell et al15 Petrou et al16
50–69
27–89
78–99
Chappell et al15 Petrou et al16
Abbreviations: DSA, digital subtraction angiography; CTA, computed tomography angiography; CE-MRA, contrast-enhanced magnetic resonance angiography.
twice daily) are recommended.17 Some studies suggest a progressive medical approach to carotid stenosis and include using aspirin/clopidogrel or aspirin/clopidogrel plus a statin in the acute setting.24,25 Acute statin treatment reduced 7-day stroke risk from 13.2 to 3.8% in patients with carotid stenosis presenting with TIA in one study.26 The Stroke Prevention by Aggressive Reduction in Cholesterol Levels Trial found that high-dose atorvastatin (80 mg daily) was associated with a 33% reduction in stroke and 56% reduction in the need for carotid revascularization compared with placebo.27
Carotid Endarterectomy Carotid endarterectomy (CEA) was introduced in 195428 and has remained a standard for carotid revascularization.5,29–33 A major factor in consideration of surgical intervention is percentage of stenosis. Class I evidence based on the studies discussed below led to the recommendation of surgical intervention as an option for symptomatic patients with > 70% stenosis on noninvasive imaging or > 50% by catheter angiography and a perioperative stroke and mortality rate of < 6%.34 The North American Symptomatic Carotid Endarterectomy Trial (NASCET), published in 1991, compared CEA to the optimal medical therapy at that time (acetylsalicylic acid (ASA) 325 mg daily). For patients with 70 to 99% stenosis, there was a 5.8% perioperative risk of stroke or death, with 2.1% of those treated by CEA resulting in disability or death.35 At 2 years, any major stroke or death occurred in 18.1% in the optimal medical therapy compared with 8% in the CEA group.35 Long-term follow-up suggested a 17.1% risk of ipsilateral disabling stroke for optimal medical therapy compared with 5.7% for CEA.30 Another analysis published in 1998
by Barnett et al19 looked at patients with symptomatic stenosis from 50 to 69%. Five-year ipsilateral stroke was found to be 22.2% in the optimal medical therapy group and 15.7% in the CEA group. For patients with < 50% carotid stenosis, surgical intervention did not demonstrate a benefit.19 The European Carotid Surgery Trial (ECST), originally reported in 1998, suggested a benefit of surgery when a cutoff of 80% carotid stenosis was used. Optimal medical therapy had a 26.5% risk of stroke at 2 years compared with 14.9% for CEA.33 The ECST was reanalyzed in 2003 to facilitate comparison with NASCET. Carotid endarterectomy reduced the 5-year risk of stroke 5.7% for 50 to 69% stenosis and 21.2% for 70 to 99% stenosis.36
Case Example 1 A 65-year-old man presented to his primary care physician with intermittent paresthesias of the left side of his body and visual auras. A CTA of the head and neck demonstrated a 70% luminal narrowing of the right internal carotid artery just distal to the bifurcation (►Fig. 1). At the time of referral, he was already taking aspirin, a statin, and three antihypertensives. He underwent an uneventful CEA and at 1-year followup, he was asymptomatic without recurrent stenosis on surveillance ultrasound.
Carotid Artery Stenting Although CEA has been considered the standard intervention for carotid stenosis, carotid artery stenting (CAS) has recently developed as a reasonable alternative. Initial studies comparing outcomes of high-risk patients with carotid artery stenosis were performed with angioplasty alone or stenting without embolic protection devices (EPD).37,38 Embolic protection devices were developed to capture or prevent any Seminars in Neurology
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CTA
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Fig. 1 (A) Sagittal computed tomography angiography (CTA) of the head and neck demonstrating significant stenosis with calcification (black arrow). (B) Axial CTA of neck demonstrating stenosis and calcification of right internal carotid artery (black arrow). (C) Coronal CTA of head and neck with significant stenosis and calcification of the right internal carotid artery (black arrow).
embolic particles released during manipulation of the diseased carotid that might lead to neurologic injury. With the development of embolic protection, outcomes of CAS have continued to improve. Embolic protection comes in three forms: (1) as a flow arrest or distal occlusion device, (2) as distal filters, and (3) as a proximal protection device.39 With a distal occlusion device, a balloon is inflated distal to the stenosis to prevent embolization of debris caused by stenting. Risks include propagation of embolic material while initially crossing the lesion to place the balloon itself and cerebral ischemia due to carotid occlusion (and so preinflation assessment of collateral circulation is recommended). Distal filters, also known as flow preservation devices, are filters placed beyond the lesion with porosity that permit blood flow, while trapping emboli released during the procedure. Flow through the carotid is not interrupted as with distal occlusion devices. There are similar challenges of crossing the lesion before protection is in place and the porous nature of the filter allowing for microemboli into the cerebral circulation. Proximal protection devices are the newest addition to the EPD repertoire. They function proximal to the lesion, thereby avoiding the necessity of crossing the lesion during a highrisk period.40 The GORE Flow Reversal System (W.L. Gore and Associates, Flagstaff, AZ) is a device that reverses flow within the carotid and diverts any emboli caused by revascularization away from cerebral circulation and into the filter of the device itself. The prospective Embolic Protection with Reverse Flow (EMPiRE) clinical study evaluated the safety and efficacy of the GORE system and found a primary endpoint (stroke, death, myocardial infarction [MI], or TIA within 30 days) rate of 4.5%, which was favorable when compared with other studies using EPDs.41 The MO.MA proximal cerebral protection device (Medtronic, Santa Rosa, CA), introduced in Europe in 2001, is another proximal protection device that endovascularly occludes the external and common carotid arteries, temporarily halting blood flow and thus preventing emboli from going to the brain. As with distal occlusion devices and GORE reversal, sufficient collateral circulation is needed for success. The prospective ProximAl PRotection with the MO.MA Device DUring CaRotid Stenting (ARMOUR) trial examined the safety Seminars in Neurology
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of MO.MA and found the 30-day rate of MI, stroke, or death to be 2.7%.42
CEA vs Stenting Whether CEA or CAS is the optimal intervention for a given patient is often unclear. Circumstances that appear to favor CAS include an irradiated neck, patients with tracheostomy, prior radical neck surgery, surgically inaccessible lesions, and post-CEA restenosis.43 In addition, the Asymptomatic Carotid Atherosclerosis Study (ACAS) and the Carotid Endarterectomy Trial (NASCET) showed increased morbidity with CEA in patients with severe contralateral carotid occlusion. This may represent another patient population that may benefit from stenting over CEA. Three recent major prospective randomized trials comparing CAS with CEA deserve special note: (1) Stenting and Angioplasty with Protection in Patients at High Risk for Endarterectomy (SAPPHIRE), (2) Carotid Revascularization Endarterectomy Versus Stenting Trial (CREST), and (3) International Carotid Stenting Study (ICSS). The SAPPHIRE trial (2004) examined CAS with EPD versus CEA in high-risk surgical patients.44 Criteria for high risk included clinically significant cardiac disease, severe pulmonary disease, contralateral carotid occlusion, and previous radical neck surgery, or neck radiation therapy and age > 80. The primary endpoint (a composite of death, stroke, or MI within 30 days and death or ipsilateral stroke at 31 days to 1 year) occurred in 12.2% of CAS-treated patients and 20.1% of CEA-treated patients (p ¼ 0.004 for noninferiority, p ¼ 0.053 for superiority).44 The study concluded that CAS was not inferior to CEA for high-risk patients with these conditions. Patients in the CEA group also had significantly more cranial nerve palsies (4.9% and 0.0%, respectively, p ¼ 0.004) and target-vessel repeat revascularizations at 1 year (CEA 4.3% and CAS 0.6%, p ¼ 0.04). A major difference in primary outcome was increased incidence of MI in the CEA group (7.5%) versus the CAS group (3.0%) with MI (p ¼ 0.07). A major criticism of the trial has been that the definition of MI was determined by blood work alone without electrocardiogram (ECG) or clinical correlation. Long-term follow-up at 3 years again did not show a significant difference in
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cumulative incidence of death, stroke, or MI from 31 days and 3 years between CAS and CEA.45 There was also no difference in target-vessel revascularization. However, SAPPHIRE is difficult to compare with other studies because 70% of the patients studied were asymptomatic and outcome data were not correlated with degree of stenosis. CREST (2010) randomized 2,502 patient trials to compare CAS and CEA.46 Nearly half of the patients enrolled were asymptomatic. Similar to the SAPPHIRE trial, the primary endpoint was a composite of stroke, MI, and death during the periprocedural period or any ipsilateral stroke within 4 years. At a median follow-up of 2.5 years, no significant difference was found in the primary endpoint that occurred in 7.2% of CAS and 6.8% of CEA patients (p ¼ 0.51).46 There were, however, statistically significant differences among the components of the primary endpoint. In the periprocedural period, CAS had a significantly higher rate of stroke than CEA (4.1% vs. 2.3%, p ¼ 0.01), which was also seen over the entire 4-year study period (10.2% vs. 7.9%, p ¼ 0.03). As in the SAPPHIRE trial, CEA had a significantly higher rate of MI than CAS (2.3% vs. 1.1%, p ¼ 0.03), which offset the difference in stroke in the primary endpoint analysis. Quality of life analyses indicated that the effects of having a stroke were worse than having a MI at 1 year.46 Of note, the authors found an association between older age and increased risk of poor outcome with CAS, which was contrary to previous assumptions that elderly high-risk patients would do better with stenting. The ICSS is a multicenter, international study that randomized 1,713 patients to CEA versus CAS.29 The long-term results are not yet published. The secondary composite endpoint of differences in stroke, death, or procedural MI within 120 days of randomization has been reported in the interim. Stenting was associated with a significantly higher risk of stroke, death, and MI than CEA (8.5% vs. 5.2%, hazard ratio [HR] 1.69 [1.16–2.45], p ¼ 0.006).29 The EPDs were used in only 72% of cases. There was virtually no difference in occurrence of procedural MI between CAS and CEA in the interim period, unlike SAPPHIRE or CREST. There was one cranial nerve palsy in CAS-treated patients and 45 in CEA patients (p < 0.0001). There were also fewer hematomas in the stenting group, 31 versus 50 for CEA (p ¼ 0.0197). A 2010 publication regarding pooled, short-term outcomes from three randomized controlled clinical trials—the Endarterectomy versus Angioplasty in Patients with Symptomatic Severe Carotid Stenosis (EVA-3S) trial, the Stent-Protected Angioplasty versus Carotid Endarterectomy (SPACE) trial, and the International Carotid Stenting Study (ICSS)—showed that in patients > 70 years old, the risk of stroke or death was 12.9% for CAS and 5.9% for CEA (p ¼ 0.0053). The same risks of stroke or death in patients < 70 years old treated with CAS were 5.8% and 5.7% for CEA, further supporting the belief that there may be an increased risk for stenting in the elderly.47
Case Example 2 A 62-year-old man with a history of coronary artery disease status post coronary artery bypass graft, lung cancer, hypertension, diabetes mellitus, chronic obstructive pulmonary disease, and left eye vision loss, presented with high-grade
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Fig. 2 (A) Lateral digitally subtracted common carotid angiogram demonstrating 90% stenosis of internal carotid artery (black arrow). (B) Lateral digitally subtracted common carotid angiogram with filter wire (black arrow) and stent providing revascularization of the internal carotid artery (white arrow).
stenosis of the left internal carotid artery. Carotid angiogram demonstrated 90% stenosis of the left internal carotid artery (►Fig. 2A). Due to his significant medical comorbidities, the patient was offered carotid stenting. A Spider X filter wire was advanced past the stenosis. Before crossing the stenosis with the stent, dilation was performed with a balloon. Subsequently, an Xact stent (Abbot Laboratories, Abbot Park, IL) was placed, significantly improving flow through the vessel (►Fig. 2B).
Summary Current literature is supportive of optimal medical therapy of antiplatelet agents, anticholesterol medications, and blood pressure control for all patients. Best medical therapy alone is optimal for symptomatic patients with < 50% stenosis. Carotid endarterectomy has been the standard of intervention and remains the preferred form of intervention. Technologies for carotid artery stenting have rapidly been progressing along with improved outcomes from this procedure. Currently, stenting is preferred for individuals with recurrent stenosis, postradiation patients, and difficult surgical cases. Improved outcomes in randomized studies may be in part due to improved optimal medical therapy.
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Symptomatic Carotid Artery Stenosis
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Symptomatic Carotid Artery Stenosis Bradley N. Bohnstedt, MD1
Ryan Dhaemers, MD2
1 Department of Neurological Surgery, Indiana University School of
Medicine, Indianapolis, Indiana 2 Department of Radiology, Indiana University School of Medicine, Indianapolis, Indiana 3 Goodman Campbell Brain and Spine, Indianapolis, Indiana
Daniel Hsu, MD3 Address for correspondence Bradley N. Bohnstedt, MD, Department of Neurological Surgery, Indiana University School of Medicine, 355 W 16th Street, Suite 5100, Indianapolis, IN 46202 (e-mail: [email protected]).
Abstract
The management of patients with extracranial carotid artery stenosis remains controversial. Randomized controlled studies established the value of carotid endarterectomy (CEA) over optimal medical therapy for patients with symptomatic carotid stenosis. For patients with carotid stenosis, optimal medical therapy includes antiplatelet agents, antihypertensives, and lipid-lowering medications along with lifestyle modifications. Some studies and experts have challenged these treatment methods and consider carotid artery stenting with distal protection as an alternative to CEA. In this article, the authors review current guidelines and supporting studies and suggest practical approaches to this common clinical problem.
Keywords
► carotid stenosis ► carotid endarterectomy ► carotid artery stenting
Carotid disease is responsible for 10 to 20% of ischemic strokes.1 Symptomatic disease refers to signs or symptoms referable to the diseased carotid artery. The last few decades have witnessed a revolution in the diagnosis and treatment of carotid disease. In this article, we will review the diagnostic studies, therapeutic options, and outcomes of symptomatic carotid artery disease.
Diagnostic Studies Diagnosis Imaging evaluation for carotid disease was first performed with conventional catheter angiography,2 and later improved to digital subtraction arteriography (DSA).3 Digital subtraction arteriography remains the gold standard; it is an invasive procedure, however, that carries a 1 to 3% complication risk.4–6 As early as 1975, noninvasive methods were developed to evaluate carotid artery stenosis.7,8 Carotid Doppler ultrasound has a sensitivity of 72 to 96% and a specificity of 61 to 100% for high-grade stenosis.9 However, its use is limited in the setting of calcification and may overestimate stenosis.10,11 The initial use of noncontrast-enhanced computed tomography (CT) of the neck was for detection of calcifications of the carotid artery in patients with transient ischemic attacks (TIAs).12 With the development of CT angiography (CTA), high-quality
Issue Theme Advanced Cerebrovascular Disease Management; Guest Editor, Jason Mackey, MD, MS
noninvasive arterial imaging became possible (►Table 1).13 Advances in magnetic resonance angiography (MRA) have allowed additional noninvasive imaging without ionizing radiation or iodinated contrast (►Table 1).14–16 When patients present with symptoms of amaurosis fugax, TIA, or stroke, the initial evaluation should include carotid Doppler.17 If > 70% stenosis is found, intervention may be justified. In symptomatic patients for whom sonography results are equivocal or nondiagnostic, CTA or MRA are indicated.17 If doubt remains in the diagnosis, DSA of the carotid should be considered. For the symptomatic patient with >50% stenosis by DSA or >70% by noninvasive imaging, the current recommendation is for intervention.18,19
Optimal Medical Therapy Optimal medical therapy for carotid artery stenosis is focused on treatment and reduction of both risk factors and thrombotic risk. Risk factor reduction includes behavioral modifications such as smoking cessation,20 exercise, and weight control.21 Tight control of hypertension (goal < 140/90),22 diabetes (hemoglobin A1c level < 6.5%),23 and hypercholesterolemia (< 100 mg/dL) further reduces risk.17 In patients with symptomatic carotid stenosis, antiplatelet agents such as daily aspirin (75–325 mg), clopidogrel (75 mg), or aspirin plus extended-release dipyridamole (25/200 mg
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DOI http://dx.doi.org/ 10.1055/s-0033-1364218. ISSN 0271-8235.
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Semin Neurol 2013;33:456–461.
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Table 1 Recommended diagnostic tests for suspected carotid stenosis Test
% Stenosis Indicating Treatment
Sensitivity (%)
Specificity (%)
References
100
100
Celesia et al3
72–96
61–100
Duncan et al7 Suwanwela et al9 Weaver et al10
70–99
46–84
39–97
Chappell et al15 Petrou et al16
50–69
20–90
63–92
Chappell et al15 Petrou et al16
DSAþ Symptomatic patients
50
Carotid Doppler
Symptomatic
70
Symptomatic
Masaryk et al48
CE-MRA Symptomatic
70–99
69–97
76–96
Chappell et al15 Petrou et al16
50–69
27–89
78–99
Chappell et al15 Petrou et al16
Abbreviations: DSA, digital subtraction angiography; CTA, computed tomography angiography; CE-MRA, contrast-enhanced magnetic resonance angiography.
twice daily) are recommended.17 Some studies suggest a progressive medical approach to carotid stenosis and include using aspirin/clopidogrel or aspirin/clopidogrel plus a statin in the acute setting.24,25 Acute statin treatment reduced 7-day stroke risk from 13.2 to 3.8% in patients with carotid stenosis presenting with TIA in one study.26 The Stroke Prevention by Aggressive Reduction in Cholesterol Levels Trial found that high-dose atorvastatin (80 mg daily) was associated with a 33% reduction in stroke and 56% reduction in the need for carotid revascularization compared with placebo.27
Carotid Endarterectomy Carotid endarterectomy (CEA) was introduced in 195428 and has remained a standard for carotid revascularization.5,29–33 A major factor in consideration of surgical intervention is percentage of stenosis. Class I evidence based on the studies discussed below led to the recommendation of surgical intervention as an option for symptomatic patients with > 70% stenosis on noninvasive imaging or > 50% by catheter angiography and a perioperative stroke and mortality rate of < 6%.34 The North American Symptomatic Carotid Endarterectomy Trial (NASCET), published in 1991, compared CEA to the optimal medical therapy at that time (acetylsalicylic acid (ASA) 325 mg daily). For patients with 70 to 99% stenosis, there was a 5.8% perioperative risk of stroke or death, with 2.1% of those treated by CEA resulting in disability or death.35 At 2 years, any major stroke or death occurred in 18.1% in the optimal medical therapy compared with 8% in the CEA group.35 Long-term follow-up suggested a 17.1% risk of ipsilateral disabling stroke for optimal medical therapy compared with 5.7% for CEA.30 Another analysis published in 1998
by Barnett et al19 looked at patients with symptomatic stenosis from 50 to 69%. Five-year ipsilateral stroke was found to be 22.2% in the optimal medical therapy group and 15.7% in the CEA group. For patients with < 50% carotid stenosis, surgical intervention did not demonstrate a benefit.19 The European Carotid Surgery Trial (ECST), originally reported in 1998, suggested a benefit of surgery when a cutoff of 80% carotid stenosis was used. Optimal medical therapy had a 26.5% risk of stroke at 2 years compared with 14.9% for CEA.33 The ECST was reanalyzed in 2003 to facilitate comparison with NASCET. Carotid endarterectomy reduced the 5-year risk of stroke 5.7% for 50 to 69% stenosis and 21.2% for 70 to 99% stenosis.36
Case Example 1 A 65-year-old man presented to his primary care physician with intermittent paresthesias of the left side of his body and visual auras. A CTA of the head and neck demonstrated a 70% luminal narrowing of the right internal carotid artery just distal to the bifurcation (►Fig. 1). At the time of referral, he was already taking aspirin, a statin, and three antihypertensives. He underwent an uneventful CEA and at 1-year followup, he was asymptomatic without recurrent stenosis on surveillance ultrasound.
Carotid Artery Stenting Although CEA has been considered the standard intervention for carotid stenosis, carotid artery stenting (CAS) has recently developed as a reasonable alternative. Initial studies comparing outcomes of high-risk patients with carotid artery stenosis were performed with angioplasty alone or stenting without embolic protection devices (EPD).37,38 Embolic protection devices were developed to capture or prevent any Seminars in Neurology
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CTA
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Fig. 1 (A) Sagittal computed tomography angiography (CTA) of the head and neck demonstrating significant stenosis with calcification (black arrow). (B) Axial CTA of neck demonstrating stenosis and calcification of right internal carotid artery (black arrow). (C) Coronal CTA of head and neck with significant stenosis and calcification of the right internal carotid artery (black arrow).
embolic particles released during manipulation of the diseased carotid that might lead to neurologic injury. With the development of embolic protection, outcomes of CAS have continued to improve. Embolic protection comes in three forms: (1) as a flow arrest or distal occlusion device, (2) as distal filters, and (3) as a proximal protection device.39 With a distal occlusion device, a balloon is inflated distal to the stenosis to prevent embolization of debris caused by stenting. Risks include propagation of embolic material while initially crossing the lesion to place the balloon itself and cerebral ischemia due to carotid occlusion (and so preinflation assessment of collateral circulation is recommended). Distal filters, also known as flow preservation devices, are filters placed beyond the lesion with porosity that permit blood flow, while trapping emboli released during the procedure. Flow through the carotid is not interrupted as with distal occlusion devices. There are similar challenges of crossing the lesion before protection is in place and the porous nature of the filter allowing for microemboli into the cerebral circulation. Proximal protection devices are the newest addition to the EPD repertoire. They function proximal to the lesion, thereby avoiding the necessity of crossing the lesion during a highrisk period.40 The GORE Flow Reversal System (W.L. Gore and Associates, Flagstaff, AZ) is a device that reverses flow within the carotid and diverts any emboli caused by revascularization away from cerebral circulation and into the filter of the device itself. The prospective Embolic Protection with Reverse Flow (EMPiRE) clinical study evaluated the safety and efficacy of the GORE system and found a primary endpoint (stroke, death, myocardial infarction [MI], or TIA within 30 days) rate of 4.5%, which was favorable when compared with other studies using EPDs.41 The MO.MA proximal cerebral protection device (Medtronic, Santa Rosa, CA), introduced in Europe in 2001, is another proximal protection device that endovascularly occludes the external and common carotid arteries, temporarily halting blood flow and thus preventing emboli from going to the brain. As with distal occlusion devices and GORE reversal, sufficient collateral circulation is needed for success. The prospective ProximAl PRotection with the MO.MA Device DUring CaRotid Stenting (ARMOUR) trial examined the safety Seminars in Neurology
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of MO.MA and found the 30-day rate of MI, stroke, or death to be 2.7%.42
CEA vs Stenting Whether CEA or CAS is the optimal intervention for a given patient is often unclear. Circumstances that appear to favor CAS include an irradiated neck, patients with tracheostomy, prior radical neck surgery, surgically inaccessible lesions, and post-CEA restenosis.43 In addition, the Asymptomatic Carotid Atherosclerosis Study (ACAS) and the Carotid Endarterectomy Trial (NASCET) showed increased morbidity with CEA in patients with severe contralateral carotid occlusion. This may represent another patient population that may benefit from stenting over CEA. Three recent major prospective randomized trials comparing CAS with CEA deserve special note: (1) Stenting and Angioplasty with Protection in Patients at High Risk for Endarterectomy (SAPPHIRE), (2) Carotid Revascularization Endarterectomy Versus Stenting Trial (CREST), and (3) International Carotid Stenting Study (ICSS). The SAPPHIRE trial (2004) examined CAS with EPD versus CEA in high-risk surgical patients.44 Criteria for high risk included clinically significant cardiac disease, severe pulmonary disease, contralateral carotid occlusion, and previous radical neck surgery, or neck radiation therapy and age > 80. The primary endpoint (a composite of death, stroke, or MI within 30 days and death or ipsilateral stroke at 31 days to 1 year) occurred in 12.2% of CAS-treated patients and 20.1% of CEA-treated patients (p ¼ 0.004 for noninferiority, p ¼ 0.053 for superiority).44 The study concluded that CAS was not inferior to CEA for high-risk patients with these conditions. Patients in the CEA group also had significantly more cranial nerve palsies (4.9% and 0.0%, respectively, p ¼ 0.004) and target-vessel repeat revascularizations at 1 year (CEA 4.3% and CAS 0.6%, p ¼ 0.04). A major difference in primary outcome was increased incidence of MI in the CEA group (7.5%) versus the CAS group (3.0%) with MI (p ¼ 0.07). A major criticism of the trial has been that the definition of MI was determined by blood work alone without electrocardiogram (ECG) or clinical correlation. Long-term follow-up at 3 years again did not show a significant difference in
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cumulative incidence of death, stroke, or MI from 31 days and 3 years between CAS and CEA.45 There was also no difference in target-vessel revascularization. However, SAPPHIRE is difficult to compare with other studies because 70% of the patients studied were asymptomatic and outcome data were not correlated with degree of stenosis. CREST (2010) randomized 2,502 patient trials to compare CAS and CEA.46 Nearly half of the patients enrolled were asymptomatic. Similar to the SAPPHIRE trial, the primary endpoint was a composite of stroke, MI, and death during the periprocedural period or any ipsilateral stroke within 4 years. At a median follow-up of 2.5 years, no significant difference was found in the primary endpoint that occurred in 7.2% of CAS and 6.8% of CEA patients (p ¼ 0.51).46 There were, however, statistically significant differences among the components of the primary endpoint. In the periprocedural period, CAS had a significantly higher rate of stroke than CEA (4.1% vs. 2.3%, p ¼ 0.01), which was also seen over the entire 4-year study period (10.2% vs. 7.9%, p ¼ 0.03). As in the SAPPHIRE trial, CEA had a significantly higher rate of MI than CAS (2.3% vs. 1.1%, p ¼ 0.03), which offset the difference in stroke in the primary endpoint analysis. Quality of life analyses indicated that the effects of having a stroke were worse than having a MI at 1 year.46 Of note, the authors found an association between older age and increased risk of poor outcome with CAS, which was contrary to previous assumptions that elderly high-risk patients would do better with stenting. The ICSS is a multicenter, international study that randomized 1,713 patients to CEA versus CAS.29 The long-term results are not yet published. The secondary composite endpoint of differences in stroke, death, or procedural MI within 120 days of randomization has been reported in the interim. Stenting was associated with a significantly higher risk of stroke, death, and MI than CEA (8.5% vs. 5.2%, hazard ratio [HR] 1.69 [1.16–2.45], p ¼ 0.006).29 The EPDs were used in only 72% of cases. There was virtually no difference in occurrence of procedural MI between CAS and CEA in the interim period, unlike SAPPHIRE or CREST. There was one cranial nerve palsy in CAS-treated patients and 45 in CEA patients (p < 0.0001). There were also fewer hematomas in the stenting group, 31 versus 50 for CEA (p ¼ 0.0197). A 2010 publication regarding pooled, short-term outcomes from three randomized controlled clinical trials—the Endarterectomy versus Angioplasty in Patients with Symptomatic Severe Carotid Stenosis (EVA-3S) trial, the Stent-Protected Angioplasty versus Carotid Endarterectomy (SPACE) trial, and the International Carotid Stenting Study (ICSS)—showed that in patients > 70 years old, the risk of stroke or death was 12.9% for CAS and 5.9% for CEA (p ¼ 0.0053). The same risks of stroke or death in patients < 70 years old treated with CAS were 5.8% and 5.7% for CEA, further supporting the belief that there may be an increased risk for stenting in the elderly.47
Case Example 2 A 62-year-old man with a history of coronary artery disease status post coronary artery bypass graft, lung cancer, hypertension, diabetes mellitus, chronic obstructive pulmonary disease, and left eye vision loss, presented with high-grade
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Fig. 2 (A) Lateral digitally subtracted common carotid angiogram demonstrating 90% stenosis of internal carotid artery (black arrow). (B) Lateral digitally subtracted common carotid angiogram with filter wire (black arrow) and stent providing revascularization of the internal carotid artery (white arrow).
stenosis of the left internal carotid artery. Carotid angiogram demonstrated 90% stenosis of the left internal carotid artery (►Fig. 2A). Due to his significant medical comorbidities, the patient was offered carotid stenting. A Spider X filter wire was advanced past the stenosis. Before crossing the stenosis with the stent, dilation was performed with a balloon. Subsequently, an Xact stent (Abbot Laboratories, Abbot Park, IL) was placed, significantly improving flow through the vessel (►Fig. 2B).
Summary Current literature is supportive of optimal medical therapy of antiplatelet agents, anticholesterol medications, and blood pressure control for all patients. Best medical therapy alone is optimal for symptomatic patients with < 50% stenosis. Carotid endarterectomy has been the standard of intervention and remains the preferred form of intervention. Technologies for carotid artery stenting have rapidly been progressing along with improved outcomes from this procedure. Currently, stenting is preferred for individuals with recurrent stenosis, postradiation patients, and difficult surgical cases. Improved outcomes in randomized studies may be in part due to improved optimal medical therapy.
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Symptomatic Carotid Artery Stenosis
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