Carotid Endarterectomy and Carotid Stenting

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CHAPTER 24 Carotid Endarterectomy and Carotid Stenting

Grace J. Wang, Ronald M. Fairman

Case Study

A 75-year-old male with a medical history significant for insulin-dependent diabetes, coronary artery disease, hypertension, hypercholesterolemia, and tobacco use presents to a vascular surgeon’s office. He reports several recent episodes of visual changes that he describes as a “shade being pulled over my right eye,” each of which lasted several seconds. On physical examination, a right carotid bruit is noted. On fundoscopic examination, small yellow plaque-like crystals are seen within the right retinal artery. A carotid duplex shows an 80% stenosis of the right internal carotid artery and a patent left internal carotid artery.

BACKGROUND

Stroke is the third leading cause of death in the United States. More than 700,000 strokes occur annually. Additionally, nonfatal strokes result in substantial morbidity and health care expenditures; the American Heart Association estimated this cost to be $18 billion annually in 1993. Strokes are broadly categorized as hemorrhagic (20%) or ischemic (80%); up to 30% of ischemic strokes attributable to carotid disease.

C. Miller Fisher, a neurologist, first recognized the relationship between atherosclerotic disease of the carotid bifurcation and symptoms of ipsilateral monocular blindness and contralateral hemiplegia in 1951. Atherosclerotic plaque formation in the carotid bulb may lead to embolization of friable plaque or thrombus and subsequent neurologic deficits. Rarely, a flow-limiting stenosis of the carotid artery results in symptomatic cerebral hypoperfusion. Because it is a manifestation of atherosclerosis, carotid disease is associated with hypertension, diabetes, hyperlipidemia, and tobacco use. Patients with carotid disease may present with transient ischemic attacks (TIAs), defined as neurologic deficits lasting less than 24 hours. These embolic events are often associated with focal motor or language and speech deficits. Alternatively, patients present with amaurosis fugax (monocular blindness secondary to embolization of the ophthalmic artery, a branch of the internal carotid artery). Physical examination of patients with carotid disease may reveal a carotid bruit, reflecting turbulent flow through a stenotic lesion. Importantly, the presence of a bruit does not reflect the severity of stenosis, and patients may have severe carotid stenoses in the absence of a bruit. Duplex examination is the most frequently used screening modality to assess carotid disease and has largely supplanted physical examination.

Carotid endarterectomy (CEA), the subject of this chapter, is a well-established mode of primary stroke prevention in patients with carotid disease. The use of carotid angioplasty and stenting has emerged as an alternative to CEA in selected patients and is discussed in brief.

INDICATIONS FOR SURGERY

I. Symptomatic Stenosis of Greater than 70%: Patients with a symptomatic stenosis of more than 70% and associated symptoms (e.g., TIAs) are offered CEA. The benefit of surgery in this population was established by several randomized controlled trials, including the North American Symptomatic Carotid Endarterectomy Trial (NASCET). This trial compared rates of stroke in patients who received surgery and in those treated with aspirin alone and showed a benefit from surgery. This finding was corroborated by subsequent trials, including the European Carotid Surgery Trial (ECST).
II. Asymptomatic Stenosis of Greater than 60%: Asymptomatic stenosis is the most common indication for CEA. The benefit of surgery in patients with asymptomatic disease was established in the Asymptomatic Carotid Atherosclerosis Study (ACAS). This study showed that surgery was more effective than medical management in preventing strokes in patients with asymptomatic carotid stenoses of more than 60%.
III. Unstable Symptoms: An ulcerated atherosclerotic plaque may act as a nidus for fresh thrombus formation. Symptoms suggesting the presence of an unstable plaque and ongoing embolization are an indication for urgent CEA (within 24 hours). Crescendo TIAs are TIAs that occur at increasingly short intervals. Complete resolution of symptoms is noted between attacks. In contrast, patients with stroke in evolution have repeated TIAs and their symptoms only partially resolve between events.

Does your patient have symptomatic or asymptomatic carotid disease?

PREOPERATIVE EVALUATION

I. Carotid duplex ultrasonography is the most commonly used modality for detecting carotid stenoses because of its widespread availability and high degree of accuracy (100% in some series). An internal carotid artery peak systolic velocity (PSV) of more than 220 cm/sec in conjunction with an internal carotid artery:common carotid artery PSV ratio of more than 4.0 suggests high-grade carotid stenosis. A peak end-diastolic velocity of more than 100 cm/sec is consistent with a stenosis of greater than 70%.
II. Magnetic resonance angiography (MRA) allows for evaluation of the origins of the great vessels, which are not well imaged with duplex ultrasound. MRA is particularly indicated if signs of subclavian artery occlusive disease, such as a disparity between right and left brachial blood pressures or a supraclavicular bruit, are noted. Symptoms associated with subclavian steal syndrome, such as arm claudication, lightheadedness, or near syncope, are likewise an indication for MRA.
III. Computed tomography angiography (CTA) can be used to delineate the extent of aortic and carotid disease in patients with normal renal function who cannot undergo MRA. CTA of the brain is also highly accurate for evaluating intracranial occlusive disease and aneurysms.

COMPONENTS OF THE PROCEDURE AND APPLIED ANATOMY

Preoperative Considerations

I. CEA can be performed under regional or general anesthesia. If the regional approach is chosen, the awake patient’s neurologic function can be grossly assessed throughout the procedure. Changes in neurologic function after clamping of the carotid artery can be addressed with immediate placement of a temporary shunt to restore cerebral perfusion. The use of general anesthesia is typically coupled with either routine shunt placement or continuous electroencephalographic (EEG) monitoring and selective shunting.
II. Placement of an arterial catheter allows for continuous blood pressure monitoring during and after CEA.
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