3 Carotid Artery Stenosis
The pre/post questions are listed below. They are all multiple choice questions with a single right answer. To best guide your learning, we have hidden the answers in a collapsible menu. Before reading the chapter, we suggest giving the questions a try, noting your answers on a notepad. After reading the chapter, return to the questions, re-evaluate your answers, and then open the collapsible menu to read the correct answer and discussion. Do not fret if you have difficulty answering the questions before reading the chapter! By the end of the chapter, we are certain you will have covered the knowledge necessary to answer the questions. There will be a teaching case at the end of the chapter. This is another opportunity to exercise your new knowledge!
Pre/Post Questions
Case Based Questions
- A 75-year-old male smoke presents with recent visual changes to his right eye that occurred yesterday. The patient reports a shading of his visual field that resulted in momentary monocular blindness followed by return to normal vision. He has a carotid duplex showing >50% diameter reduction to his right internal carotid artery and >80% stenosis to his left internal carotid artery. What treatment should be offered to his patient?
A. Emergent DC cardioversion to treat any underlying arrythmia.
B. Left carotid endarterectomy with shunt placement.
C. Left carotid TCAR.
D. Right carotid endarterectomy.
E. Placement on Apixaban and measurement of PF4 with medical management.
- A 50-year-old female patient with >80% right internal carotid artery stenosis presents to clinic for her first postoperative visit after carotid endarterectomy (CEA). She has no interval neurologic events since her discharge, has a soft neck with a clean incision. During your neurologic exam you notice an unintentional, subtle tongue deviation to the side of surgery. What is the most likely facial nerve involved in this finding?
A. Vagus Nerve.
B. Hypoglossal Nerve.
C. Glossopharyngeal Nerve.
D. Long Thoracic Nerve.
E. Hering’s Nerve.
- During the initial evaluation of a patient with high grade symptomatic carotid disease, you notice that the patient has internal carotid plaque on that side this is above the angle of the mandible at the 1st cervical vertebral body (C1). This appears to be too high to access through open surgery. The patient has no know history of coronary artery disease, has a preserved ejection fraction and good functional status. He has a low-density lipoprotein level (LDL) of 200 mg/dL. What is the best treatment option for this individual?
A. Transfemoral carotid artery angioplasty with placement on ASA only.
B. Carotid artery enterectomy with shunt placement.
C. Daily ASA therapy without any type of statin or antihypertensive therapy.
D. Trancarotid artery revascularization (TCAR) surgery with dual antiplatelet therapy.
E. No treatment is indicated.
- A 60-year-old otherwise healthy woman, with no underlying comorbidities has a right carotid artery bruit on physical examination. She is concerned that she is at risk for stroke. She denies any episodes of vision changes, upper or lower extremity deficits, or speech impairments. She currently takes 81mg of aspirin daily, along with a multivitamin. What is the next step in management for this patient?
No further treatment necessary.
Carotid duplex.
CT angiogram head and neck.
Neurology evaluation.
Addition of statin therapy.
- A 65-year-old man who is right-handed is undergoing evaluation for a coronary artery bypass graft surgery (CABG). As part of his workup, a carotid duplex is performed which demonstrates a chronic right carotid occlusion and a >80% stenosis of his left carotid artery. He has no history of ocular or cerebrovascular events. He has hypercholesterolemia and well-controlled hypertension. What is the next best step for this patient?
Proceed with the CABG as planned and continue medical therapy with aspirin and statin.
Left carotid endarterectomy before the CABG.
Place the patient on dual antiplatelet therapy, in addition to statin therapy.
Left TCAR (transcarotid stent) after the CABG.
Place the patient on anticoagulation.
- A 55-year-old woman has a past medical history of coronary artery disease status post coronary stenting in 2019, hypertension, hyperlipidemia, and previous smoking history of 60 pack-years. Her cardiologist sends her for a carotid duplex which demonstrates a 50-69% carotid stenosis on the left side, and mild atherosclerosis on the right side. She denies any prior signs or symptoms of stroke or transient ischemic attack. How should this patient’s carotid disease be managed?
Left carotid endarterectomy, along with aspirin/statin therapy.
Left transfemoral carotid stent, along with dual antiplatelet/statin therapy.
Aspirin and statin therapy only, and routine surveillance carotid duplexes.
Aspirin, statin therapy, blood pressure management, and routine surveillance carotid duplexes.
No further management is indicated.
Operative Footage Questions
These questions are associated with the carotid endarterectomy (CEA) footage (short version) found at the bottom of the chapter.
- What is the first muscle layer encountered in a CEA (i.e. the first muscle deep to skin)?
A. Sternocleidomastoid
B. Digastric
C. Platysma
D. Scalene
- What structure is not found in the carotid sheath?
A. Internal jugular vein
B. External jugular vein
C. Common carotid artery
D. Vagus nerve
- In what order do you unclamp the carotid vessels at the end of a carotid endarterectomy?
A. External carotid artery → common carotid artery → internal carotid artery
B. Common carotid artery → internal carotid artery → external carotid artery
C. Internal carotid artery → external carotid artery → common carotid artery
D. Internal carotid artery → common carotid artery → external carotid artery
Introduction
Hemispheric stroke related to carotid artery stenosis is a leading cause of both disability and death in the United States. Underlying etiologies for stroke include occlusive or hemorrhagic events with roughly 80% being related to occlusive pathology through embolus or in-situ thrombosis, the remaining 20% attributable to hemorrhage. Roughly 15% of stroke victims have a transient ischemic attack (TIA) that fully resolved prior to a later stroke event. Risk factors for carotid plaque formation are related to age, smoking, coronary artery disease, diabetes, hyperlipidemia, hypertension and family history of stroke. Due to carotid bulb anatomy, the most common area of plaque formation is within the proximal internal carotid artery. As plaque stenosis increases over time, the systolic velocity increases to maintain flow volumes which intensifies shear stress. This shear stress increases likelihood of plaque rupture, platelet aggregation and thromboembolization. There are multiple seminal studies that describe cohort comparisons of asymptomatic and symptomatic carotid artery stenosis with outcomes related to optimal medical management alone or as adjunct to surgical repair. Symptomatic carotid stenosis is described as carotid stenosis >50% with unilateral stroke, TIA or amaurosis fugax on the side of carotid disease. Amaurosis fugax is historically described as shade coming down across one eye on the side of stenosis to produce partial or complete, painless monocular visual loss related to transient retinal ischemia. Amaurosis fugax may be bilateral in the case of bilateral, symptomatic carotid artery stenosis.
Etiology
Atherosclerosis is the most common cause for the development of carotid artery disease. This process is defined by deposition of lipid-laden plaque at the carotid bifurcation, and potentially across a larger territory of the common carotid, external carotid, and internal carotid arteries. This plaque may contain varying degrees of calcification and/or thrombus. The mechanisms by which atherosclerosis at the carotid bifurcation may lead to stroke or TIA are: occlusion (cessation of blood flow to the internal carotid artery) or embolization (plaque debris break off and travel through the internal carotid artery to the brain). There are various risk factors which may contribute to the degree of atherosclerosis and its progression. These include history of cigarette smoking, hyperlipidemia, coronary artery disease, diabetes, hypertension, advanced age, and family history of carotid disease or stroke.
Diagnostics and Imaging
Three primary imaging modalities are used to evaluate carotid artery stenosis with the lowest cost option being color flow duplex ultrasound (DSA) that allows a physician to determine peak systolic and end diastolic velocities throughout the carotid bifurcation. Based on the internally validated vascular laboratory criteria of the institution, these velocities can be correlated to ranges of degree of stenosis, with high grade stenosis defined as >70-80%. Since the modality is based primarily on velocity range, it cannot give exact stenosis such as 66%. The modality can also provide adjunct information about the blood flow waveforms in each arterial segment, as well as whether that flow is laminar or turbulent with utilization of color flow imaging. Limitations of this imaging include technician skill, inability to obtain optimal angle of Doppler interrogation for velocity determination, shadowing from heavily calcified lesions, poor visualization due to patient habitus and tortuosity.
Axial imaging options include both computed tomography angiogram (CTA) and magnetic resonance angiogram (MRA). Both of these options require some form of intra-arterial contrast, either iodinated contrast or gadolinium, respectively. However, they offer a fuller perspective of relevant anatomy and a more precise determination of stenosis within the limitations of the modality, with MRA often overestimating the degree of stenosis due to intrinsic properties of MRA imaging acquisition. Both CTA and MRA, although superior to DSA in determination of exact degree of plaque stenosis and arterial anatomy, sacrifice the physiologic information offered through DSA that speak to flow patterns, flow direction and turbulence. Axial imaging of CTA and MRA can define patency but do not speak to the dynamic nature of blood flow or directionality of flow.
Definitive determination of flow and directionality can be augmented to a carotid artery stenosis workup by diagnostic angiography. This requires femoral artery access and includes contrast administration, as well as a small risk of periprocedural embolization. However, it offers additional physiologic evaluation that might not be present in DSA and that is inherently lacking in CTA and MRA studies.
Asymptomatic Carotid Atery Stenosis Screening
The 2021 SVS clinical practice guidelines outline the following recommendations. In asymptomatic patients who qualify for carotid artery stenosis screening, duplex ultrasound is the recommended choice over CTA, MRA, or other imaging modalities.
Routine screening is not recommended for clinically asymptomatic carotid artery stenosis for individuals without significant risk factors for carotid disease.
Screening is recommended for clinically asymptomatic carotid artery stenosis in individuals with significant risk factors** for carotid disease. High-risk groups include:
- Patients with lower extremity peripheral artery disease (PAD)
- Patients undergoing coronary artery bypass surgery (CABG)
- Patients aged >= 55 years with at least two traditional atherosclerotic risk factors (hyperlipidemia, hypertension, etc.)
- Patients aged >= 55 years and active cigarette smoking
- Patients with diabetes, hypertension, or coronary artery disease (CAD)
- Patients with clinically occult cerebral infarction noted on brain imaging studies.
The presence of a carotid bruit increases the likelihood of detecting significant stenosis. Asymptomatic patients with an abdominal aortic aneurysm (AAA) or previous radiotherapy to the neck who do not meet the criteria of any of the high-risk groups above do not require screening. It has been shown that the prevalence of carotid stenosis increases proportionally with the number of risk factors present.
Treatment
Carotid Artery Endarterectomy (CEA)
This procedure has been performed since the 1950s, either by plaque endarterectomy and patch angioplasty or primary arterial repair. To prevent arterial restenosis, patch angioplasty has become the standard of arterial closure after plaque removal. The procedure can involve cerebral monitoring including electroencephalography (EEG), transcranial Doppler (TCD) and stump pressure monitoring or be performed awake to directly monitor patient motor response. Endarterectomy and patch repair can be performed under a “clamp and sew” mentality or with an arterial shunt to maintain cerebral perfusion. Risks include cardiopulmonary risk of acute myocardial ischemia, <3% perioperative risk of neurologic event, neck hematoma or cranial nerve injury of roughly 5-10% affecting the vagus, marginal mandibular, recurrent laryngeal or hypoglossal nerves.
Carotid Artery Stenting (CAS)
Transfemoral Carotid Artery Stenting (TFCAS) with Embolic Protection
Transfemoral stenting requires some type of protection from embolization including a distal internal carotid artery retrievable filter or flow arrest procedure to prevent cerebral embolization during stent placement with or without angioplasty.
Transcarotid Artery Revascularization (TCAR)
Treatment of a carotid stenosis that avoids aortic arch manipulation involving direct common carotid artery exposure and sheath placement to allow for transcarotid stent delivery to the internal carotid artery. The common carotid artery sheath is connected to a femoral vein sheath so that the natural arterial pressure gradient reverses flow across the distal internal carotid artery driving blood and possible embolus into the arterial tubing circuit and across a filter before it reenters the venous circulation. As FDA approval for the device was delivered in 2016, the technology is less than 10 years old without robust long-term follow up data. This technique offers a lower perioperative stroke risk than transfemoral stenting, for multiple reasons including lack of transaortic arch manipulation and great vessel cannulation which can result in embolus prior to placement of an internal carotid artery embolic protection device.
Optimal Medical Management
Understandably, optimal medical management requires full risk evaluation of the individual patient in question including other comorbidities, drug allergies, compliance, etc. We have listed a few broad recommendations to follow that offer general guidance surrounding the dynamic target of optimal medical management for arterial disease.
Antiplatelet Therapy
- ASA offers a 22% risk reduction in major vascular events with no difference in protection based on dosage (81 versus 325 mg).
- Clopidogrel can be used as an adjunct or alternative to ASA, but the added benefit from dual antiplatelet combination in asymptomatic carotid artery stenosis is unproven.
Anticoagulants
- Only useful for prevention of cardioembolic strokes due to arrhythmia or prosthetic valve.
Hypertension Treatment
- Recommended blood pressure range of <130/80 with individual antihypertensive regimen based on other comorbidities and patient risk factors.
Diabetic Control
- In accordance with best practice for diabetes management, the patient’s hemoglobin A1c should be <7.0
Smoking Cessation
- Treatments offered include nicotine replacement therapy (NRT), varenicline or bupropion as first line agents.
Hyperlipidemia Management
- Regimen goals of LDL <100mg/dl, or <70mg/dl depending on risk profile.
Outcomes and Surveillance
Asymptomatic carotid stenosis
- The historically touted Asymptomatic Carotid Atherosclerosis Study (ACAS) demonstrated that patients with >60% carotid stenosis who underwent CEA benefited significantly from stroke risk reduction at 5 years (5.1% for CEA vs. 11% for optimal medical therapy consisting of aspirin alone).
- More recent studies suggest that with the current optimal medical management, which consists of antiplatelet medication and statin therapy, 5-year stroke risk is highest in patients with >70% carotid stenosis, and therefore this patient population would benefit from carotid endarterectomy.
- Patients who are deemed high risk, either due to an anatomic (such as surgically inaccessible bifurcation or restenosis after previous CEA) or physiologic findings (congestive heart failure, severe coronary artery disease, or chronic obstructive pulmonary disease), may be considered for TCAR given the equivocal results of perioperative stroke or death at 1.3%, as compared to CEA.
- Asymptomatic patients with significant risk factors found to have moderate stenoses (50%-79%) should be followed every 6-months to detect disease progression. High risk patients with <50% stenosis can be followed-up annually.
Symptomatic carotid stenosis
- Patients who have >50% carotid stenosis and have developed symptoms of TIA or stroke were found to benefit from CEA in the pivotal North American Symptomatic Carotid Endarterectomy Trial (NASCET) because of the significant 2-year stroke risk reduction as compared to optimal medical management (15.7% vs. 22.2%.). An even greater stroke risk reduction was seen in patients with >70% carotid stenosis (9% CEA vs. 26% medical management).
- Current management of patients with symptomatic >50% carotid stenosis who are low/standard risk is carotid endarterectomy over transfemoral carotid stenting (TFCAS), as there are no studies to date which have shown benefit of TFCAS.
- Patients who are deemed high risk, as defined above, may be considered for TCAR over TFCAS due to the significantly lower incidence of in-hospital stroke and death (1.6% vs. 3.1%).
- Post-operative surveillance (by duplex ultrasound) after open (CEA) or endovascular (TF-CAS) repair of the carotid artery is strongly recommended by the SVS to monitor for signs of restenosis in the repaired artery or atherosclerotic disease progression in the unoperated, contralateral artery. Duplex ultrasound testing is recommended within 30 days of the procedure, then every 6 months for 2 years, then annually.
- Restenosis <50% warrants the regular surveillance protocol; 50-99% warrants closer follow-up, confirmation with a CTA, and possible angiographic evaluation; 100% restenosis warrants surveillance and medical treatment of the contralateral carotid artery.
- It should be noted, there is some debate as to the economic and medical value of continuing post-operative duplex ultrasound surveillance after successful CEA with patch closure when the immediate post-operative duplex was normal or showed minimal disease.
Teaching Case
Scenario
An 81 year old male with a significant smoking history and prior three vessel CABG five years ago, presents with monocular right eye blindness that occurred two days ago. He has no prior ophthalmologic conditions and states that he describes the process of a veil coming down over his right eye with resolution about a minute later with complete return of normal vision at that point. He denies any other symptoms during the event or since, such as motor or sensory deficits, speech, etc. He did not think much of the event but presented after his wife told him to see someone about the event.
Exam
HEENT: No prior neck incisions, good cervical extension.
Cardiac: Regular rate and rhythm. Healed sternotomy scar.
Pulmonary: Clear to auscultation throughout.
Abdominal: Soft and nontender.
Neurologic: All cranial nerves 2-12 intact, no lateralizing deficits, 5/5 strength to all extremities.
Optho: No visual deficits at 20 feet from eye chart.
Imaging
Duplex Ultrasound (Peak Systolic Velocity/End Diastolic Velocity)
| Location | Right | Left |
|---|---|---|
| Proximal ICA | 540/240 cm/s | 120/45 cm/s |
| Mid ICA | 230/145 cm/s | 119/37 cm/s |
| Distal ICA | 240/110 cm/s | 110/23 cm/s |
Duplex Report: Based on color flow duplex imaging there is evidence of 80-99% stenosis of the right internal carotid artery segment and <50% stenosis to the contralateral side.
Discussion Points
However, we feel this chapter contains all the necessary information to answer the questions. If not, please let us know!
- Please explain the pathophysiology of the visual event for this patient? Describe why it can be termed amaurosis fugax. Ensure understanding that amaurosis fugax is the result of carotid plaque embolization to the retina.
- Please list the patient’s risk factors for carotid disease? What is best medical management to optimize these risk factors?
- Is this patient asymptomatic or symptomatic based on the clinical scenario presented?
- What next steps should be pursued to offer effective and timely treatment to this patient? Please discuss adjunct imaging such as CTA or MRA to determine anatomic characteristics of the lesions such as ulceration, vessel patency, level (accessible or high lesions), etc.
- What surgical managements could be suggested to this patient? Please include a discussion of carotid endarterectomy, transfemoral stenting or TCAR.
- What medications should be started in this scenario? Please consider ASA, Plavix, statin medications, etc.
- What are some possible relevant complications of surgical intervention, including periprocedural stroke risk?
Key Articles
Ricotta JJ, Aburahma A, Ascher E, Eskandari M, Faries P, Lal BK; Society for Vascular Surgery. Updated Society for Vascular Surgery guidelines for management of extracranial carotid disease. J Vasc Surg. 2011 Sep;54(3):e1-31.(Ricotta et al. 2011)
AbuRahma AF, Avgerinos EM, Chang RW, Darling RC 3rd, Duncan AA, Forbes TL, Malas MB, Murad MH, Perler BA, Powell RJ, Rockman CB, Zhou W. SOCIETY FOR VASCULAR SURGERY CLINICAL PRACTICE GUIDELINES FOR MANAGEMENT OF EXTRACRANIAL CEREBROVASCULAR DISEASE. J Vasc Surg. 2021 Jun 18. (AbuRahma et al. 2022)
Endarterectomy for asymptomatic carotid stenosis.Executive Committee for the Asymptomatic Carotid Atherosclerosis Study. JAMA 1995;273(18):1421-8. (Walker 1995)
Beneficial effect of carotid endarterectomy in symptomatic patients with high-grade stenosis. North American Symptomatic Carotid Endarterectomy (NASCET) Trial Collaborators. N Engl J Med 1991;325(7):445-53.(“Beneficial Effect of Carotid Endarterectomy in Symptomatic Patients with High-Grade Carotid Stenosis” 1991)
Howard D.P.J., Gaziano L., Rothwell P.M.: Risk of stroke in relation to degree of asymptomatic carotid stenosis: a population-based cohort study, systematic review, and meta-analysis. Lancet Neurol 2021; 20: pp. 193-202.(Howard, Gaziano, and Rothwell 2021)
Additional Resources
Audible Bleeding Content
- Audible Bleeding Exam Prep: Cerebrovascular Chapter
- Audible Bleeding has an episode covering the NASCET trial. Listen to it below and find additional information here, or find the episode wherever you listen to podcasts.
- The Audible Bleeding Holding Pressure Series has an episode about carotid endarterectomy. The Holding Pressure Series is designed specifically for medical students! Listen to the episode below and find additional information here, or find the episode wherever you listen to podcasts.
Websites
- TeachMe Surgery: Carotid Artery Disease
Serious Games
Touch Surgery Simulations.
- Must download the Medtronic Touch Surgery mobile application to access the modules. Available for Apple and Android mobile devices.
- Carotid Endarterectomy
- Carotid Artery Stenting
Gore Combat Manual
The Gore Medical Vascular and Endovascular Surgery Combat Manual is an informative and entertaining read intended as a vascular surgery crash course for medical students, residents, and fellows alike. Highly accessible with a thoughtfully determined level of detail, but lacking in learning activities (e.g. questions, videos, etc.), this resource is a wonderful complement to the APDVS eBook.
Please see pages 119-125.
Operative Footage
Developed by the Debakey Institute for Cardiovascular Education & Training at Houston Methodist. YouTube account required as video content is age-restricted. Please create and/or log in to your YouTube account to have access to the videos.