Carotid endarterectomy

Definition

Carotid endarterectomy is a surgical procedure to treat obstruction of the carotid artery caused by atherosclerotic plaque formation.

Purpose

The purpose of surgical therapy for vascular disease is to prevent stroke. Stroke can be caused by atherosclerosis of the carotid arteries located in the neck. Atherosclerosis is a degenerative disease of the cardiovascular system, which can occur in the carotid arteries in the neck, resulting in plaques of lipids, cholesterol crystals, and necrotic cells. The plaques in the carotid arteries can result in disease by embolizing, thrombosing, or causing stenosis (narrowing of artery). The plaques in the carotid arteries can cause disease if they obstruct a vessel or get dislodged and obstruct another area.

Precautions

The procedure is contraindicated in patients with an occluded carotid artery and in cases of severe neurologic deficit resulting from cerebral infarction. Additionally, the procedure is not performed in persons with concurrent medical illness severe enough to limit life expectancy. During the operation, precautions should be taken to prevent intraoperation movement of the atherosclerotic plaque. This can occur by excessive manipulation of the carotid bifurcation (the anatomical point where the internal and external carotid is joined together). The internal carotid will extend from the neck and penetrate the brain (to provide the brain with blood), whereas the external carotid will form other smaller arteries to provide blood to structures within the neck region. Atherosclerotic plaques are fragile especially if they are ulcerated. During the operation the surgeon must carefully dissect free other attached vessels such as the common carotid, internal carotid, and external carotid arteries with minimal physical manipulation of the affected carotid vessel.

Description

The first successful carotid endarterectomy was performed by DeBakey in 1953. During the past 40 years the procedure has been optimized and has become the most frequently performed peripheral vascular operation in the United States. There are more than 130,000 cases of carotid endarterectomy performed annually in the United States. Several randomized prospective clinical trials have conclusively established both the safety and efficacy of carotid endarterectomy and its superiority for favorable outcomes when compared to the best medical management. Largely due to credible scientific and clinical research, there has been a very large increase in the performance of this procedure over the past ten years. It is understandable that the procedure is common since it is utilized for the treatment of stroke, which is a condition that is associated with high morbidity (death rates) and is frequent. Carotid endarterectomy is the most common surgical procedure in the United States utilized to treat stenosis (narrowing) of the carotid artery. There are approximately more than 700,000 incident strokes annually and 4.4 million stroke survivors. There are 150,000 annual deaths from stroke. Approximately 30% of stroke survivors die within the first 12 months. Within 12 years approximately 66% will eventually die from stroke, making this condition the third leading cause of death in the United States. The cause of atherosclerosis is unknown, but injury to the arteries can occur from infectious agents, hyperlipidemia, cigarette smoking, and hypertension. The aggregate cost associated with approximately 400,000 first strokes in 1990 was $40.6 billion. Among those who have experienced one stroke, the incidence of stroke within five years is 40–50%. Research as of 2002 concludes that carotid endarterectomy remains the standard of care for the treatment of carotid artery atherosclerosis.

Surgical Description

A vertical incision is made in front of the sternocleidomastoid muscle providing optimal exposure of the surgical field. The line of the incision (10 cm in length) begins at the mastoid process and extends to approximately one to two fingerbreadths above the sternal notch. The exact location of carotid bifurcation can be determined before operation by ultrasound studies or arteriography. Muscles and nerves within the area are carefully displaced to allow access to the diseased area (plaque). When the surgical field is cleared of adjacent anatomical structures the endarterectomy portion of the procedure is carried out. This is accomplished by an incision in the common carotid artery at the site below the atherosclerotic plaque. The surgeon then uses an angled scissor (called a Potts scissor) to incise the common carotid artery through the plaque into the normal internal carotid artery. It is vital to extend the arterial incision (arteriotomy) above and below the atherosclerotic plaque. The surgeon utilizes a blunt dissecting instrument called a Penfield instrument to dissect the atherosclerotic plaque from the attachment to the arterial wall.

Arterial Reconstruction

After removing the atherosclerotic plaque, primary closure with sutures, or closure with a vein or prosthetic patch, is performed. Research indicates that utilization of a prosthetic patch is more favorable than suture closing. During this stage of the operation flushing is important to remove debris and air. Vein patch is advantageous because this type of closure reduces the risk of thrombus accumulation and possibly prevents perioperative stroke.

Preparation

As part of the preoperative preparation, routine laboratory tests for blood chemistry (complete blood count, electrolytes), kidney function tests, lipid profiles, and special blood tests to monitor clotting times are ordered by the clinician. Measurement of clotting times is important because blood thinner medications are typically given to patients preoperatively. Neuroimaging studies of the head are important in symptomatic patients to identify old or new cerebral infarcts. Carotid ultrasound studies are the screening test of choice accepted by surgeons to evaluate for carotid stenosis. An electrocardiogram (ECG) is important for evaluating past myocardial infarction and ischemic cardiac changes. The importance of ECG monitoring cannot be overemphasized given that the most common cause of postoperative mortality (death) is cardiac arrest. Positioning of the patient is also important. The operating table should be horizontal without head elevation. The head should be partially turned to the opposite side of the surgical field. It may be advantageous to place a rolled towel under the patient's shoulders to exaggerate neck extension. Gentle preparation and cleaning of operative fields should ensure minimal physical manipulation and pressure to avoid dislodging fragments of atherosclerotic plaque. The goals for anesthetic management include control of blood pressure and heart rate, protection of the brain and heart from ischemic insult, and relief of surgical pain and operative stress responses. Routine monitors (ECG and pulse oximetry to measure blood oxygen levels) and oxygen face mask are placed prior to anesthetic induction. Typically, any commonly utilized anesthetic and muscle relaxants (nondepolarizing) can be administered for carotid endarterectomy.

Aftercare

Aspirin therapy should be initiated at the time of diagnosis of transient ischemic attack (TIA), amaurosis fugax (transient visual loss), or stroke. Recent research from the prospective Aspirin and Carotid Endarterectomy (ACE) trial suggests that low dose (80 to 325 mg per day) of aspirin is optimal in preventing thromboembolic events after carotid endarterectomy. After carotid endarterectomy the patient's blood should be tested (complete blood count and electrolytes). Cardiac function can be monitored with ECG recordings. Frequent neurologic assessment is essential as well as hemodynamic monitoring (with the goal of maintaining blood pressure at its prior range). The patient should be observed for hemotoma formation which could cause airway obstruction. Antiplatelet therapy is necessary. About two weeks postoperatively patients are evaluated for neurologic and wound complications. Carotid ultrasound studies are performed after six months postoperatively and annually scheduled.

Risks

There are several important complications that can occur after carotid endarterectomy. Stroke or transient neurologic deficit can occur within 12 to 24 hours after operation. These conditions are usually caused by thromboembolic complications, which typically originate from the endarterectomy site or damaged vessels that were involved during the operative procedure (internal, common, and external carotid arteries). In approximately 33–50% of patients, hypertension or hypotension can occur. Wound complications such as hemotoma formation can cause pain and tracheal (wind pipe) deviation, which can impair normal breathing. During surgery, damage to vital nerves can occur, such as cervical nerves which supply sensation to the neck region. Patients may complain of numbness in the lower ear, lower neck, and upper face regions. Damage to the hypoglossal nerve (which provides innervations of the tongue), can produce deviation of the tongue to the paralyzed side and speech impairment. Additionally, the problem can reoccur, resulting in stenosis and symptoms.

Normal results

The normal progression of results following carotid endarterectomy is the prevention of stroke which is approximately 1.6% (two-year stroke risk), compared to 12.2% for patients who are medically treated. The results of the Asymptomatic Carotid Atherosclerosis Study (ACAS) reveal that the incidence of stroke for the postsurgical group (those receiving carotid endarterectomy) was 5.1%; for the group treated medically, the incidence was 11%. As with all surgical procedures, it is important for patients to select a surgeon who has expertise in the particular procedure and in the management of the condition. Some studies indicate that surgeons should perform 10 to 12 carotid endarterectomies every year in order to maintain surgical expertise and management skills.

Resources

BOOKS

Miller, Ronald D., et al, eds. Anesthesia. 5th ed. Churchill Living Stone, Inc. 2000.

Townsend, Courtney M. Sabiston Textbook of Surgery. 16th ed. W. B. Saunders Company, 2001.

PERIODICALS

Barnett, Henry J. M. "The appropriate use of carotid endarterectomy." Canadian Medical Association Journal 166 (April 2002): 9.

Gross, Cary, P. "Relation between prepublication release of clinical trial results and the practice of carotid endarterectomy." Journal of the American Medical Association 284 (December 2000): 22.

Mullenix, Philip. "Carotid Endarterectomy remains the gold standard." American Journal of Surgery 183, no. 59 (May 2002).

Perler, Bruce A. "Carotid Endarterectomy: The 'gold standard' in the endovascular era." Journal of the American College of Surgeons 194, no. 1 (January 2002).

Walker, Paul M. "Carotid Endarterectomy: applying trial results in clinical practice." Canadian Medical Association Journal 157 (1997).

ORGANIZATIONS

National Stroke Association. 9707 E. Easter Lane, Englewood, Colarado 80112. 303-649-9299 or 1-800-strokes; Fax: 303-649-1328. http://www.stroke.org.

Laith Farid Gulli, M.D.

Robert Ramirez, D.O.

The carotid artery is the large vertical artery in red. The blood supply to the common carotid artery starts at the arch of the aorta (left) or the subclavian artery (right). The common carotid artery divides into the internal carotid artery and the external carotid artery. Plaque often builds up at that division, and a carotid endarterectomy cuts open the artery and removes the plaque.

Section of carotid artery with plaque. Blood flows from the common carotid artery (bottom), and divides into the internal carotid artery (left) and external carotid artery (right). The atherosclerotic plaque is the dark mass on the left, which would be removed in an endarterectomy.

Carotid endarterectomy (CEA) is a surgical procedure used to prevent stroke, by correcting stenosis in the common carotid artery. Endarterectomy is the removal of material on the inside (end-) of an artery.

Atherosclerosis causes plaque to form in the carotid arteries, usually at the fork where the common carotid artery divides into the internal and external carotid artery. The plaque can build up in the inner surface of the artery (lumen), and narrow or constrict the artery. Pieces of the plaque emboli can break off and travel up the internal carotid artery to the brain, where it blocks circulation, and can cause death of the brain tissue.

Sometimes the plaque causes symptoms first. The symptoms are temporary or transitory strokes, known as transient ischemic attacks (TIAs). By definition, TIAs last less than 24 hours; after 24 hours they are called strokes. Symptomatic stenosis has a high risk of stroke within the next 2 days. National Institute for Health and Clinical Excellence (NICE) guidelines recommend that patients with moderate to severe (50-99% blockage) stenosis, and symptoms, should have "urgent" endarterectomy within 2 weeks.^[1]

When the plaque doesn't cause symptoms, patients are still at higher risk of stroke than the general population, but not as high as patients with symptomatic stenosis. The incidence of stroke, including fatal stroke, is 1-2% per year. The surgical mortality of endarterectomy ranges from 1-2% to as much as 10%. Two large randomized clinical trials have demonstrated that carotid surgery done with a 30 day stroke and death risk of 3% or less will benefit asymptomatic patients with ≥60% stenosis who are expected to live at least 5 years after surgery. ^[2][3] Surgeons are divided over whether asymptomatic patients should be treated with medication alone or should have surgery.^[4][5]

In endarterectomy, the surgeon simply opens the artery and removes the plaque. A newer procedure, endovascular angioplasty and stenting, threads a catheter up from the groin, around the aortic arch, and up the carotid artery. The catheter uses a balloon to expand the artery, and inserts a stent to hold the artery open. In several clinical trials,the 30-day incidence of heart attack, stroke, or death was significantly higher with stenting than with endarterectomy (9.6% vs. 3.9%) [1][2]. The role of carotid stenting in non-high-risk patients has yet to be answered, with clinical trials ongoing, including the Carotid Revascularization Endarterectomy versus Stenting Trial (CREST)[3] funded by the National Institutes of Health (NIH). Presently, most experts agree that endartectomy is the preferred treatment for most patients, with stenting procedures reserved only for highly selected candidates.

Contents 1 Procedure 2 History 3 Indications 4 Contra-indications 5 Complications 6 References 7 External links

Procedure

The internal, common and external carotid arteries are clamped, the lumen of the internal carotid artery is opened, and the atheromatous plaque substance removed. The artery is closed, hemostasis achieved, and the overlying layers closed. Many surgeons lay a temporary shunt to ensure blood supply to the brain during the procedure. The procedure may be performed under general or local anaesthesia. The latter allows for direct monitoring of neurological status by intra-operative verbal contact and testing of grip strength. With general anaesthesia indirect methods of assessing cerebral perfusion must be used, such as electroencephalography (EEG), transcranial doppler analysis and carotid artery stump pressure monitoring. At present there is no good evidence to show any major difference in outcome between local and general anaesthesia.

Non-invasive procedures have been developed, by threading catheters through the femoral artery, up through the aorta, then inflating a balloon to dilate the carotid artery, with a wire-mesh stent and a device to protect the brain from embolization of plaque material. The FDA has approved 5 carotid stent systems as safe and effective in patients at increased risk of complications for neck surgery. In the SAPPHIRE study, Yadav concluded that this procedure, known as carotid stenting, was non-inferior to carotid endarterectomy in total adverse events, and lowered event rates for major stroke, cranial nerve palsy, and myocardial infarction, in patients at high risk for surgery.^[6] It is the consensus of experts in the field that carotid artery stenting should be considered an option for patients who require carotid artery revascularization to prevent stroke and who are at increased risk of having surgical complications. ^[7]

History

Surgical intervention to relieve atherosclerotic obstruction of the carotid arteries was first successfully performed by Dr. Michael DeBakey in 1953 at the Methodist Hospital in Houston, TX.^[8] Since then, evidence for its effectiveness in different patient groups has accumulated. In 2003 nearly 140,000 carotid endarterectomies were performed in the USA (Halm).

Indications

The aim of CEA is to prevent the adverse sequelae of carotid artery stenosis secondary to atherosclerotic disease, i.e. stroke. As with any prophylactic operation, careful evaluation of the relative benefits and risks of the procedure is required on an individual patient basis. Peri-operative combined mortality and major stroke risk is 2 – 5%.

Carotid stenosis is diagnosed with ultrasound doppler studies of the neck arteries, magnetic resonance angiography (MRA) or computed tomography angiography (CTA). The circle of Willis typically provides a collateral blood supply. Surgical management of symptomatic stenoses has a much higher therapeutic index with regard to asymptomatic lesions.

The North American Symptomatic Carotid Endarterectomy Trial (NASCET) and the European Carotid Surgery Trial (ECST) are both large randomized class 1 studies which have helped define current indications for carotid endarterectomy. The NASCET found that for every six patients treated, one major stroke would be prevented at two years (i.e. a number needed to treat (NNT) of six) for symptomatic patients with a 70 – 99% stenosis, where percent stenosis was defined as:^[9]

percent stenosis = ( 1 - ( minimal diameter ) / ( poststenotic diameter ) ) x 100%.

Symptomatic patients with less severe carotid occlusion (50 – 69%) had a smaller benefit, with a NNT of 22 at five years (Barclay). In addition, co-morbidity adversely affects the outcome; patients with multiple medical problems have a higher post-operative mortality rate and hence benefit less from the procedure. For asymptomatic patients (those without TIA or strokes) the European asymptomatic carotid surgery trial (ACST) found that asymptomatic patients may also benefit from the procedure, but only the group with a high grade stenosis (60% or more). For maximum benefit patients should be operated on soon after a TIA or stroke, preferably within the first month.

Contra-indications

The procedure cannot be performed in case of:

• Complete internal carotid artery obstruction (because there is no benefit to treating chronic occlusion).
• Previous stroke on the ipsilateral side with heavy sequelae, because there is no point in preventing what has already happened.
• Patient deemed unfit for the operation by the anaesthesiologist.

Complications

About 3% of asymptomatic and 6% of symptomatic patients are expected to suffer stroke or death as a result of either the surgery or carotid stenting. Other surgical complications include Hemorrhage of the wound bed which is potentially life-threatening, as swelling of the neck due to hematoma could compress the trachea. Rarely, the hypoglossal nerve can be damaged during surgery. This is likely to result in fasciculations developing on the tongue and paralysis of the affected side: on sticking it out, the patients tongue will deviate toward the affected side. Another rare but potentially serious complication is hyperperfusion syndrome due to the sudden increase in perfusion of the vasculature distal to stenosis.^[10]

References

1. ^ Sharon Swain, Claire Turner, Pippa Tyrrell, Anthony Rudd on behalf of the Guideline Development Group, Diagnosis and initial management of acute stroke and transient ischaemic attack: summary of NICE guidance, BMJ 2008;337:a786, doi:10.1136/bmj.a786 (Published 24 July 2008)
2. ^ Executive Committee for the Asymptomatic Carotid Atherosclerosis Study (ACAS). Endarterectomy for asymptomatic carotid artery stenosis. Jama. 1995;273:1421-1428.
3. ^ Halliday A, Mansfield A, Marro J, Peto C, Peto R, Potter J, Thomas D. Prevention of disabling and fatal strokes by successful carotid endarterectomy in patients without recent neurological symptoms: randomised controlled trial. Lancet. 2004;363:1491-1502.
4. ^ Clinical Decisions: Management of Carotid Stenosis, N Engl J Med 358:1617-1621
5. ^ Drug Therapy Gains Favor to Avert Stroke, By THOMAS M. BURTON, Wall Street Journal, MARCH 3, 2009. Layman's summary of surgery vs. medication-only debate.
6. ^ Yadav JS, Wholey MH, Kuntz RE, et al. (October 2004). "Protected carotid-artery stenting versus endarterectomy in high-risk patients". N. Engl. J. Med. 351 (15): 1493–501. doi:10.1056/NEJMoa040127. PMID 15470212. 
7. ^ White CJ, Beckman JA, Cambria RP, Comerota AJ, Gray WA, Hobson RW, 2nd, Iyer SS. Atherosclerotic Peripheral Vascular Disease Symposium II: controversies in carotid artery revascularization. Circulation. 2008;118:2852-2859.
8. ^ Debakey Bio
9. ^ Barnett HJ, Taylor DW, Eliasziw M, et al. (November 1998). "Benefit of carotid endarterectomy in patients with symptomatic moderate or severe stenosis. North American Symptomatic Carotid Endarterectomy Trial Collaborators". The New England Journal of Medicine 339 (20): 1415–25. PMID 9811916. http://content.nejm.org/cgi/pmidlookup?view=short&pmid=9811916&promo=ONFLNS19. 
10. ^ van Mook WN, Rennenberg RJ, Schurink GW, et al. (2005). "Cerebral hyperperfusion syndrome". Lancet Neurol 4 (12): 877–88. doi:10.1016/S1474-4422(05)70251-9. PMID 16297845. 

External links

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