Historical Background
Although Carrea, Molins, and Murphy performed a successful carotid resection in 1951 and DeBakey completed a successful carotid endarterectomy (CEA) in 1953, the potential benefit of surgical treatment for symptomatic carotid occlusive disease was first highlighted by Eastcott, Pickering, and Rob in 1954. Use of a carotid shunt was then described by Al-Naaman, Carton, and Cooley in 1956. Two large multicenter randomized trials, the North American Symptomatic Carotid Endarterectomy Trial and the European Carotid Surgery Trial, have since demonstrated that CEA reduces the risk of stroke in patients with ipsilateral symptomatic carotid stenosis. The efficacy of CEA in asymptomatic patients has also been confirmed in three randomized clinical trials that included patients with moderate to severe stenosis.
Indications
CEA is indicated to prevent stroke in patients with carotid bifurcation occlusive disease. Multiple randomized prospective studies support CEA for: (1) asymptomatic patients with carotid stenosis of more than 60%, and (2) symptomatic patients with a history of recent transient ischemic attack (TIA) or amaurosis fugax and ipsilateral carotid stenosis of more than 50%.
Additional indications for CEA have been reported. Given limited available evidence, the decision to recommend treatment should be based upon the surgeon’s complication rate and patient preference. Specifically, the benefits of CEA are less established for: (1) patients with carotid stenosis of more than 50% and nonhemispheric symptoms, vertebrobasilar symptoms, stroke in evolution, or a completed acute stroke, and (2) symptomatic patients with an ulcerated carotid plaque and ipsilateral carotid stenosis of less than 50%.
Preoperative Preparation
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The use of aspirin (81-325 mg/day) or clopidogrel (75 mg/day) during the preoperative and postoperative periods is an evidence-based adjunct to diminish perioperative complications.
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Several studies attest to the protective effect of perioperative statins.
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Perioperative imaging may consist of a duplex scan alone, provided that the quality control aspects of the noninvasive vascular laboratory have been verified and the surgeon can evaluate both the technical adequacy and the original data of the study. Additional imaging may consist of magnetic resonance angiography, computed tomography (CT) angiography, or conventional catheter-based angiography. However, the inherent risk of the latter and the current reliability of CT angiography means invasive angiography is rarely needed.
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Evaluation of cardiac risk is recommended by clinical profiling or in select patients through use of noninvasive stress testing.
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Evaluation of vocal cord function should be performed in patients with a history of prior CEA.
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Prophylactic antibiotics are advisable.
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Nasotracheal intubation and mandibular subluxation should be considered for exposure of the distal internal carotid artery (ICA).
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Intraoperative arterial line monitoring of blood pressure is recommended.
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Intraoperative cerebral monitoring may be used to indicate a need for a carotid shunt.
Pitfalls and Danger Points
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Stroke
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The performance of a technically perfect operation is the most important variable in stroke prevention.
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Perioperative antiplatelet therapy is an evidence-based adjunct to diminish risk of stroke.
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Cranial nerve (CN) injury
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Hematoma
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Restenosis
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Recurrence of stenosis is more common in women and small arteries.
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Patch angioplasty is an evidence-based adjunct to diminish risk of restenosis.
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Operative Strategy
Avoiding Intraoperative Stroke
The perioperative combined mortality and major stroke risk for CEA in all patient subgroups ranges between 2% and 5%. This risk is less for asymptomatic patients (<3%), increases for those who have had a recent TIA, and is greatest for patients who present with a stroke in evolution or recent stroke.
The following considerations should be parts of the operative strategy to reduce the risk of intraoperative stroke:
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Timing of intervention in the symptomatic patient. Patients with moderate to severe (>50%) stenosis and symptoms should have “urgent” endarterectomy within 2 weeks. Timing of CEA in patients with an established stroke is a matter of clinical judgment, with the size of the infarct on brain imaging an important variable. Most patients with minor stroke can have an indicated CEA performed during the same hospital admission. In the rare case of a patient requiring bilateral endarterectomies the second procedure can be performed 2 weeks after the initial operation.
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Operative technique. Manipulation of the carotid bifurcation should be avoided, and a “no-touch” technique should be applied to the lesion.
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Intraoperative hypotension and arrhythmias. Lidocaine can be injected into the area of the carotid sinus nerve to prevent bradyarrhythmias and hypotension during exposure of the carotid bifurcation. However, this maneuver may be associated with postoperative reflex hypertension.
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Carotid shunts. Some surgeons advocate routine carotid shunting, whereas others prefer the selective use of a shunt, noting that fewer than 10% of patients display ischemic symptoms during intraoperative occlusion of the carotid artery. In the awake patient symptoms of ischemia may manifest as the inability to follow verbal commands or as on-table seizure activity. Under general anesthesia, a change in cerebral monitoring (e.g., electroencephalogram, cerebral oximetry, or transcranial Doppler) can be used as an indication for shunting. Systolic blood pressure should be maintained between 120 and 180 mm Hg.
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Securing the endarterectomy endpoint. If the transition at the distal endpoint of the endarterectomy is not smooth, a distal intimal flap may be present that should be secured with 7-0 polypropylene tacking sutures. Careful visualization of the endpoint may require additional exposure of the distal ICA and extension of the arteriotomy. Saline irrigation confirms that the flap is adequately secured. An important technical principle is to remove all disease so that the endarterectomy “endpoint” occurs in the anatomically normal distal ICA.
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Avoidance of residual stenosis. Routine patch closure is supported by randomized prospective trials and should be performed to minimize the risk of residual distal stenosis. This risk is accentuated in women with small arteries. Although we do not routinely perform completion intraoperative imaging, Duplex ultrasound has been advocated in some centers to exclude the presence of an intimal flap or residual stenosis.
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Management of carotid kinks and coils. Excessive length of the ICA may be associated with a coil or kink at or distal to the site of occlusive disease. After removal of the plaque, redundancy of the ICA may lead to an accentuated bend or narrowing at the distal endpoint of the arteriotomy. This may be treated by resection and shortening of either the common carotid artery or the ICA. Shortening of the common carotid artery requires the presence of redundancy in both the ICA and the external carotid artery (ECA). Alternatively, eversion CEA is a convenient way to deal with such redundancy.
Avoiding Cranial Nerve Injuries
The incidence of nerve injury as a result of CEA that persists beyond hospital discharge is approximately 4%, with most deficits resolving over the subsequent few months. Injury may occur because of transection, excessive traction, or electrocauterization. Injuries to the hypoglossal (CN XII), vagus (CN X), and marginal mandibular branch of the facial nerve (CN VII) are most common, whereas the spinal accessory nerve (CN XI) and glossopharyngeal nerves (CN IX) are rarely injured. Several factors contribute to a failure to identify and properly protect the CNs:
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Anatomic variability. The vagus nerve usually lies posterior to the common carotid artery but occasionally may be found anterior to the artery. It should be distinguished from the ansa hypoglossi nerve upon opening of the carotid sheath and exposure of the common carotid artery. An anterior vagus nerve needs to be mobilized laterally.
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Short, fat neck. The hypoglossal nerve crosses the ICA at a variable distance from the bifurcation. A low-lying hypoglossal may be injured during division of the common facial vein. Otherwise, the nerve is at risk for injury during dissection through lymphovascular tissue in the upper medial portion of the operative field. Identification of the hypoglossal nerve is facilitated by following the ansa hypoglossi nerve to its junction with the hypoglossal trunk.
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High carotid bifurcation. The glossopharyngeal nerve courses between the ICA and the internal jugular vein, lying deep to the styloid process and attached muscles. It is at risk for injury during removal of the styloid process to expose the distal ICA. Confining dissection to the periadventitial tissue of the ICA minimizes the risk of injury. The spinal accessory nerve exits the skull with the glossopharyngeal and vagus nerves and pierces the sternocleidomastoid (SCM) muscle superiorly before continuing inferiorly until it reaches the trapezius muscle. The nerve is at risk of injury during distal dissections or with excessive traction on the upper extent of the SCM muscle.
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Excessive dissection. The superior laryngeal nerve courses behind the ECA. Encircling the artery at its most proximal point lessens the risk of injury.
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Placement of the skin incision. The marginal mandibular branch of the facial nerve may be injured if the incision is placed less than one fingerbreadth from the angle of the jaw. Traction or retractors at the superior extent of the incision should be directed superior and lateral, rather than hooking the mandible, which increases the risk of injury to the marginal mandibular branch. The greater auricular nerve may be injured during superior extension of the skin incision.
Operative Technique
Choice of Anesthesia
CEA can be performed under local, regional, or general anesthesia. General anesthesia is recommended for patients who may be anxious or have difficult anatomy. Randomized trials have shown no evidence that a specific anesthetic technique is associated with reduced operative morbidity or mortality.
Incision and Position
The patient is positioned at the edge of the table of the affected side. The neck is extended, and the head is turned to opposite the side of the intended incision and placed upon a soft rubber ring ( Fig. 6-1 , A ). Elevation of the shoulders with a rolled sheet or “thyroid bag” enhances neck extension, especially in patients with short, broad necks. The upper chest, lower face, and lower ear are prepped and draped. An incision paralleling the anterior margin of the SCM muscle affords maximum exposure of the entire cervical course of the carotid artery. A common error is to carry the inferior aspect of the incision too medially, allowing the larynx to interfere with exposure. The incision should be curved slightly along a skin crease, should be extended just inferior to the lobe of the ear at its distal end, and may need to be extended to the mastoid in distal, difficult lesions. This posterior displacement of the incision, one fingerbreadth below the angle of the jaw, helps avoid injury to the marginal mandibular branch of the facial nerve.
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