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Atherosclerotic Disease of the Carotid Artery
Article Last Updated: Jul 17, 2006
AUTHOR AND EDITOR INFORMATION
Section 1 of 12  
Author: Niten Singh, MD, Assistant Professor of Surgery, Uniformed Services University of the Health Sciences; Fellow, Section of Vascular Surgery, Georgetown University/Washington Hospital Center
Niten Singh is a member of the following medical societies: American College of Surgeons, American Medical Association, and Society for Vascular Surgery
Coauthor(s):
Sean D O'Donnell, MD, Director, Department of Surgery, Section of Vascular Surgery, Washington Hosptial Center;
David L Gillespie, MD, FACS, RVT, DMCC, Associate Professor of Surgery, Chief, Division of Vascular Surgery, Uniformed Services University of the Health Sciences, F Edward Hebert School of Medicine; Chief and Program Director, Department of Vascular Surgery, Walter Reed Army Medical Center;
James M Goff, MD, Assistant Chief, Department of Surgery, Walter Reed Army Medical Center; Assistant Professor, F Department of Surgery, F Edward Hebert School of Medicine, Uniformed Services University of the Health Sciences
Editors: Richard M Stillman, MD, FACS, Honorary Medical Staff, Northwest Medical Center; Former Chief of Staff and Medical Director, Wound Healing Center, Department of Surgery, Northwest Medical Center; Francisco Talavera, PharmD, PhD, Senior Pharmacy Editor, eMedicine; Vincent Lopez Rowe, MD, Assistant Professor of Surgery, Department of Surgery, Division of Vascular Surgery, University of Southern California Medical Center; Paolo Zamboni, MD, Professor of Surgery, Chief of Day Surgery Unit, Chair of Vascular Diseases Center, University of Ferrara, Italy; William H Pearce, MD, Chief, Division of Vascular Surgery, Violet and Charles Baldwin Professor of Vascular Surgery, Department of Surgery, Northwestern University School of Medicine
Author and Editor Disclosure
Synonyms and related keywords:
atherosclerotic disease of the carotid artery, atherosclerosis, stroke, transient ischemic attacks, TIAs, cerebral infarction, cerebral intermittent claudication, extracranial carotid disease, carotid plaque, angioplasty, endarterectomy, hypertension, carotid bruit, diabetes, smoking, atrial fibrillation, obesity, hyperlipidemia, homocysteine, embolization
Atherosclerosis is a degenerative disease of the arteries resulting in plaques consisting of necrotic cells, lipids, and cholesterol crystals. These plaques can result in symptoms by causing a stenosis, embolizing, and thrombosing. Atherosclerosis is a diffuse process with a predilection for certain arteries. This article describes the history and impact of this process as it occurs in the extracranial carotid artery.
History of the Procedure
The ancient Greeks recognized the importance of the extracranial carotid artery and named it from the Greek word karoo, which means to stupefy. In 1875, Growers described a patient with right hemiplegia that he attributed to an occluded left carotid artery. In 1914, Hunt emphasized the relationship between extracranial carotid disease and stroke using the phrase cerebral intermittent claudication. The surgical management of stroke was suggested in 1951 by Fisher who stated the following: "It is even conceivable that some day vascular surgery will find a way to bypass the occluded portion of the artery during the period of ominous fleeting symptoms."
The initial report of a successful surgical resection of a carotid plaque and primary anastomosis came from Eastcott, Pickering, and Rob in 1954. In 1975, DeBakey reported the 19-year follow-up of a carotid endarterectomy, the current procedure used to surgically manage atherosclerotic disease of the carotid bulb.
Problem
Stroke from any cause represents the third leading cause of death in the United States. Half a million new strokes occur each year in the United States, resulting in approximately 150,000 deaths. Stroke is the leading cause of serious long-term disability in the United States. Direct and indirect cost of stroke in the United States in 1997 was estimated at $40 billion.
Frequency
Incidence of new stroke is approximately 160 cases per 100,000 population per year. The incidence and mortality rate of stroke have reached a plateau over the past 10 years.
The risk of stroke increases with age, hypertension, the presence of a carotid bruit, diabetes, smoking, atrial fibrillation, obesity, hyperlipidemia, and elevated homocysteine level.
Etiology
Ninety percent of all extracranial carotid lesions are due to atherosclerosis.
The exact cause of atherosclerosis is unknown, and it may be the result of multiple etiologies. This concept has been referred to as the response to injury hypothesis. Infectious agents, hypertension, hyperlipidemia, and cigarette smoking have been cited as potential causes of atherosclerosis.
Other etiologies for carotid lesions include the following:
- Aneurysms
- Arteritis
- Carotid dissection
- Coils and kinks
- Fibromuscular dysplasia
- Radiation
- Vasospasm
Pathophysiology
Currently, embolization is considered the most common mechanism causing ischemic strokes from atherosclerotic lesions in the carotid bulb. Thrombosis and low flow are other possible mechanisms.
Stroke is one of the most devastating complications of carotid stenosis. However, carotid stenosis is not the only cause of stroke. In fact, consider that 45% of strokes in patients with asymptomatic stenosis of 60-99% may be caused by lacunar infarcts or cardiac emboli.
Clinical
- Amaurosis fugax (transient visual loss)
- Transient ischemic attacks (TIAs)
- Crescendo TIAs
- Stroke-in-evolution
- Cerebral infarction
Indications for carotid endarterectomy based on prospective randomized trials
- Symptomatic patients with greater than 70% stenosis: Clear benefit was found in the North American Symptomatic Carotid Endarterectomy Trial (NASCET); ipsilateral stroke in 2 years was 9% with surgery and 26% with medical management.
- Symptomatic patients with greater than 50-69% stenosis: Benefit is marginal and appears to be greater for male patients.
- Asymptomatic patients with greater than 60% stenosis: Benefit is significantly less than symptomatic patients with greater than 70% stenosis.
Note
- Available literature includes considerable overlap in the percent of stenosis used as the threshold for carotid endarterectomy. In general, symptomatic patients with greater than 50% stenosis and healthy, asymptomatic patients with greater than 60% stenosis warrant consideration for carotid endarterectomy.
- Symptomatic trials include patients with TIAs or minor strokes within 3 months of entry.
The carotid artery on the right originates from the innominate artery and on the left directly from the aortic arch. The carotid artery enlarges in the mid neck, forming the carotid bulb. It then bifurcates into the external and internal carotid arteries. The carotid sinus and carotid body are located at the bifurcation (see Image 1).
Contraindications to carotid endarterectomy include the following:
- Patients with a severe neurologic deficit following a cerebral infarction
- Patients with an occluded carotid artery
- Concurrent medical illness that would significantly limit the patient's life expectancy
Lab Studies
- CBC count
- Electrolytes, BUN, creatinine
- Lipid profile
- Prothrombin time (PT)/activated partial thromboplastin time (aPTT): Heparin is administered during carotid endarterectomy, and knowing the PT/aPTT preoperatively is important.
Imaging Studies
- CT scan or MRI of the head: All symptomatic patients should have a scan of the head to rule out other intracranial lesions and identify the presence of new and old cerebral infarcts.
- Carotid duplex
- Carotid duplex, with or without color, is the screening test of choice to evaluate for carotid stenosis.
- Many surgeons will operate on the results of a carotid duplex alone if the laboratory has credentials and is validated.
- Carotid magnetic resonance angiography
- Carotid magnetic resonance angiography (MRA) has a tendency to overstate the significance of the stenosis.
- Its exact role is not well defined; it may be useful in collaborating the finding of an occluded carotid with duplex.
Other Tests
- Electrocardiogram
- Evidence of prior myocardial infarction (MI) and ischemic changes are important to identify.
- The most common cause of mortality following carotid endarterectomy is MI.
Diagnostic Procedures
- Arch and carotid arteriography
- It was used in the NASCET to evaluate the percent of stenosis.
- The diameter of the narrowest portion of the lesion is divided by the normal internal carotid artery diameter distal to the lesion.
- This procedure may be associated with a 1-2% risk of stroke.
Medical therapy
- Antiplatelet agents
- Aspirin (30–1350 mg qd) irreversibly acetylates the cyclooxygenase of platelets, thus inhibiting platelet synthesis of thromboxane A2. Prostacyclin production in the endothelium is reduced, but this effect is reversible and short-lived. A reduction in TIAs, stroke, and death in men was shown in the Canadian Cooperative Study Group.
- Ticlopidine (250 mg bid) is a thienopyridine that irreversibly alters the platelet membrane and inhibits platelet aggregation. It is approximately 10% more effective than aspirin. Toxicity includes neutropenia and diarrhea.
- Clopidogrel (75 mg qd) is similar to ticlopidine; risk of neutropenia is low.
- Anticoagulation: Warfarin (titrated international normalized ratio [INR] 2–3) use in patients with noncardiac emboli is controversial.
- For the indications listed above (see Indications for carotid endarterectomy based on prospective randomized trials), medical management was found to be inferior to carotid endarterectomy.
Surgical therapy
Endovascular therapy
- Carotid angioplasty and stenting
- Carotid angioplasty and stenting has emerged as a viable option in the treatment of carotid artery stenosis. Rapid growth and technologic advancements have allowed this procedure to become a treatment strategy, particularly in high-risk patients.
- Numerous studies, including the Stenting and Angioplasty with Protection in Patients at High Risk for Endarterectomy (SAPPHIRE) trial, have found that CAS is not inferior to CEA.
- CAS is indicated in patients with a high-grade stenosis who are deemed high risk, such as patients with synchronous carotid and coronary artery disease, postsurgical restenosis, high lesions not amenable to surgical access, or a history of prior irradiation to the neck.
- Procedural details
- The procedure is perfomed in either an operating room with C-arm capabilities or an angiographic suite.
- Local anesthesia with limited sedation is used so that the patient's neurologic status can constantly be monitored.
- Femoral artery access is achieved and an arch arteriogram performed. The affected side is cannulated and selective carotid arteriograms are then performed. Next, a long sheath is placed over a wire into the common carotid artery and a 0.014 inch filter wire is placed into the internal carotid distal to the lesion to provide for embolic protection. Next, after appropriate sizing, the lesion is pre-dilated quickly with a small balloon. The stent is then placed and postdilated with a larger balloon. A completion arteriogram is than performed to ensure that the lesion has been treated and that no other abnormalities exist within the internal carotid or cerebral views. The procedure is completed and the access site in the femoral artery is typically closed with a closure device.
- The patient is usually monitored overnight and discharged the next day.
- Carotid endarterectomy
Preoperative details
- Cardiac evaluation
- Patients with carotid artery stenosis have a high incidence of concomitant coronary artery disease.
- Adherence to the American Heart Association's recommendations regarding cardiac evaluation for noncardiac surgery should be followed. In summary, they recommend a functional assessment on all patients with a history of new- onset angina and new symptoms following coronary angioplasty or bypass.
- Nondiabetic patients younger than 70 years with no cardiac symptoms and normal findings on ECG may undergo carotid endarterectomy without further cardiac workup.
- Preoperative imaging studies
- Imaging studies should be used to determine the extent of stenosis and to evaluate for kinks and coils that may affect the conduct of the operation (see Imaging Studies). Many surgeons who work with certified laboratories proceed with surgery based on the carotid duplex alone. If any doubt exists regarding the degree of stenosis or the distal extent of the disease, an arch and carotid arteriogram is performed.
- The extent of the disease also should be noted, with particular attention to the superior extent of the stenosis. This may impact the type of anesthesia chosen and reveal the need for additional measures to expose an unusually high lesion.
Intraoperative details
- Anesthesia
- Local anesthesia has the advantage of allowing direct evaluation of the patient's neurologic status without sophisticated monitoring. This enables the surgeon to operate on the majority of patients without the need for a shunt, which is a technical nuisance and may pose an increased risk of stroke to the patient.
- General anesthesia has the advantage of improved airway control and patient comfort during prolonged operations. However, it does require the use of routine or selected shunting, and selective shunting requires the use of electroencephalography, stump pressures, and transcranial Doppler or some other form of cerebral monitoring to assess the need for a shunt.
- Incision
- A vertical incision should be made along the anterior border of the sternocleidomastoid muscle.
- An oblique incision should be made in the skin fold over the carotid bifurcation.
- Endarterectomy
- The endarterectomy is carried out in a smooth plane in the media of the artery.
- The most important aspect of this portion of the procedure is to obtain a smooth, tapering endpoint on the internal carotid. Occasionally, tacking sutures will be required to accomplish this.
- Shunt (see Anesthesia)
- Closing
- The endarterectomy is closed either primarily or with a patch.
- The technical result should be verified by completion angiography or duplex.
Postoperative details
- CBC and electrolytes should be obtained, and ECG should be performed.
- Frequent neurologic assessment should be carried out.
- Hemodynamic monitoring with focus on maintaining the patient's blood pressure at its preoperative range should be instituted.
- Observe the patient for a hematoma that may compromise the airway.
- Antiplatelet therapy is necessary.
Follow-up
- Cardiac ischemia
- Cranial nerve injury
- Hematoma with or without airway compromise
- Hypertension and hypotension
- Perioperative stroke
- Recurrent stenosis
Cranial nerve injuries occur in 2-7% of patients. Recurrent laryngeal and hypoglossal nerve dysfunctions are the most common.
Postoperative stroke occurs in 1-5% (NASCET 5%) of patients.
The perioperative mortality rate is 0.5-1.8%.
Recurrent stenosis occurs in 1-20% of cases, and reoperation is necessary in 1-3% of cases.
Following a successful carotid endarterectomy, the 2-year stroke risk in the NASCET was 1.6%, compared with 12.2% for the medically managed patients.
In the NASCET, the cumulative risk of an ipsilateral stroke was 9% for the surgical patients and 26% for the medically managed patients.
In the Asymptomatic Carotid Atherosclerosis Study (ACAS), the 5-year risk for ipsilateral stroke was 5.1% for the surgical group compared with 11% for the medical group. The stroke risk of arteriography was attributed to the surgical group and was 1.2%.
In the Stenting and Angioplasty with Protection in Patients at High Risk for Endartertectomy (SAPPHIRE) trial, carotid stenting was found to not be inferior to carotid endarterectomy in patients with severe stenosis and coexisting conditions.
Recent meta-analysis revealed that protected (use of embolic protection wire) carotid angioplasty and stenting was associated with a 30-day stroke and death rate of 2.4%.
Carotid angioplasty and stenting research will continue to evolve, and studies are underway to evaluate its role in asymptomatic patients with high grade stenosis.
As industry and interest from numerous specialties continues in carotid angioplasty and stenting, the devices available will continue to evolve.
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Atherosclerotic disease of the carotid artery. Arteriogram of the aortic arch and its branches. |
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Atherosclerotic disease of the carotid artery. Arteriogram of a carotid stenosis. |
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Atherosclerotic disease of the carotid artery. Atherosclerotic plaque removed at the time of carotid endarterectomy (areas of ulceration with thrombus and intraplaque hemorrhage present). |
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Atherosclerotic disease of the carotid artery. Carotid artery exposed prior to carotid endarterectomy (coil present in the internal carotid artery). |
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Atherosclerotic disease of the carotid artery. Carotid artery following endarterectomy and prior to closure (tapered endpoint and smooth appearance of the lumen). |
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Atherosclerotic disease of the carotid artery. Carotid artery following Dacron patch angioplasty. |
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Oblique view of the left carotid artery demonstrating lesion within internal carotid artery. |
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Placement of stent into internal carotid artery. Note filter wire in upper photos (dots at top of internal carotid artery). |
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Angioplasty after stent placement; again, note filter wire protecting distal carotid artery. |
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Completion arteriogram displaying improvement in diameter of internal carotid artery. |
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Color flow duplex revealing an 80-99% left carotid stenosis and a normal right carotid. |
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Atherosclerotic Disease of the Carotid Artery excerpt Article Last Updated: Jul 17, 2006
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