CHAPTER 24 Carotid Endarterectomy and Carotid Stenting
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.
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.
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.
III. Despite the low incidence of surgical site infection after carotid endarectomy, antibiotic prophylaxis is indicated because of the morbidity associated with infections when they do occur. Most surgeons use a prosthetic patch to close the arteriotomy. Infection of the patch necessitates reoperation and patch excision. Antibiotics are administered within 1 hour before incision.
Patient Positioning and Preparation
II. The patient is placed in the supine position with an inflatable bag under the shoulders. This results in neck extension, which moves the carotid bifurcation downward and anteriorly, facilitating exposure.
III. The table is placed in “beach chair” position (i.e., the hips and knees are flexed), and the table is placed in reverse Trendelenburg position (Fig. 24-1).
Incision and Exposure
I. The CEA procedure is frequently performed through an incision along the anterior border of the sternocleidomastoid muscle, with a slight posterior curve away from the greater auricular nerve superiorly (Fig. 24-2). Alternatively, a curvilinear or hockey stick incision is used, which may provide for better cosmesis.
IV. The facial vein, a branch of the internal jugular vein that typically crosses over the carotid bifurcation, is identified and divided (Fig. 24-3). Care is taken to avoid injuries to the 12th cranial nerve (CN XII), which often lies immediately posterior to the facial vein.
V. The common, internal, and external carotid arteries are dissected free from surrounding tissues and encircled with vessel loops. The superior thyroid artery, which is the first branch of the external carotid, is likewise encircled with a vessel loop.
VI. CN XII, which typically crosses over the external and internal carotid arteries approximately 1.5 cm above the carotid bulb, is identified and preserved. The vagus nerve (CN X) is identified within the carotid sheath; it usually resides posterior to the common carotid artery but can occasionally be identified more laterally or even anteriorly.
VII. Aggressive retraction is avoided to prevent traction injuries to CN X, the hypoglossal nerve (CN XII), and the marginal mandibular branch of CN VII (Fig. 24-4).
Figure 24-2 Incision for carotid endarterectomy and its relationship to the carotid bifurcation.
(From Rutherford RB: Vascular Surgery, 6th ed. Philadelphia, Saunders, 2005.)
Endarterectomy
II. The internal, common, and external carotid arteries are sequentially clamped. An abnormal EEG reading at this juncture is an indication for the use of a shunt.
III. An arteriotomy is made at the carotid bifurcation and extended proximally and distally (into the internal carotid artery) beyond the area of gross disease. If appropriate, a shunt is placed in the lumen of the internal carotid artery distally and the common carotid artery proximally to allow for continuous blood flow during the endarterectomy.
IV. Plaque is dissected off of the artery wall with a blunt dissector. The appropriate plane of dissection removes diseased intima from the media at the level of the internal elastic lamina. This plane is most easily established proximally, at the carotid bulb opposite the external carotid artery, where disease is typically most severe (Fig. 24-5).
V. The distal aspect of the plaque is visualized and separated from the intima of the adjacent, normal artery, leaving a smooth residual surface. Occasionally, the endarterectomy leaves behind a flap of intima, which, if left alone, may serve as a nidus for postoperative thrombus formation. Fine suture may be used to tack down a residual intimal flap.
Arterial Reconstruction and Wound Closure
I. The arteriotomy is closed with a patch of polyester, polytetrafluoroethylene, bovine pericardium, or autogenous vein. The edges of the arteriotomy are sewn to the patch with a running suture.
II. Before completion of the arteriotomy closure, the clamps on the external, internal, and common carotid arteries are sequentially released briefly to flush out debris and air. The arterial reconstruction is then completed.
III. The surgical site is inspected for hemostasis, and a pulse in the internal carotid artery is confirmed.
VI. Before extubation, neurologic function is grossly assessed. Once the patient is extubated, a more extensive neurologic examination is performed to exclude contralateral motor or sensory disturbances. An attempt is made to elicit signs associated with injuries to CN X (vocal weakness), CN XII (tongue deviation), and the marginal mandibular branch of CN VII (lip droop).
COMPLICATIONS
I. Perioperative stroke occurs in a small, but finite number of patients. Etiologies include embolization of debris during dissection, thrombosis resulting from creation of an intimal flap or other technical errors, and reperfusion injury. If the patient emerges from anesthesia with a neurologic deficit or has a deficit within 24 hours of surgery, operative re-exploration is typically performed to exclude the presence of an intimal flap and correct technical problems. If the findings on exploration are negative, a thromboembolic event is more likely. A CT of the head is performed to rule out a hemorrhagic stroke. In the absence of intracranial hemorrhage, heparin therapy is initiated.
II. Reperfusion injury is believed to result from rupture of chronically dilated small vessels and capillaries after restoration of blood flow. Such injuries are often heralded by the clinical triad of ipsilateral headache, seizure, and intracerebral edema or hemorrhage, and are most often seen between 48 and 72 hours after surgery. Hypertension may contribute to the pathogenesis of these injuries, and blood pressure should therefore be tightly controlled postoperatively. Patients with contralateral internal carotid artery occlusion are at elevated risk for reperfusion injuries.
III. Neck hematoma may occur in the face of inadequate hemostasis or systolic hypertension during emergence from anesthesia. Large neck hematomas may cause airway compromise. Stridor or difficulty breathing should prompt emergent exploration of the neck incision and evacuation of the hematoma.
CAROTID ANGIOPLASTY AND STENTING
III. Arterial access is obtained through placement of an arterial sheath, usually into the right common femoral artery.
IV. A series of wire and catheter manipulations is used to position a shuttle sheath into the mid-common carotid artery. An angiogram is performed to help delineate the anatomy. A distal embolic protection device is positioned in the distal internal carotid artery.
V. Stents are deployed across the lesion and across the carotid bifurcation, covering the external carotid artery.
VI. Balloon angioplasty of the stent is then performed. Manipulation of the carotid bulb may result in profound bradycardia, which is effectively treated with atropine.
VII. A completion angiogram is performed to confirm adequate treatment of the lesion and restoration of flow. The embolic protection device is removed under fluoroscopic guidance. All catheters and wires are removed, and the sheath is pulled back into the external iliac artery and secured in place.
. Endarterectomy for asymptomatic carotid artery stenosis [Executive Committee for the Asymptomatic Carotid Atherosclerosis Study. JAMA. 1995;173:1421-1428.
Ferguson GG, Eliasziw M, Barr HW, et al. The North American Symptomatic Carotid Endarterectomy Trial: Surgical results in 1415 patients. Stroke. 1999;30:1751-1758.
Krupski WC, Moore WS. Indications, surgical technique and results for repair of extracranial occlusive lesions. In Rutherford RB, editor: Vascular Surgery, 6th ed, Philadelphia: Saunders, 2005.
Moore WS. Extracranial cerebrovascular: the carotid artery. In Moore WS, editor: Vascular and Endovascular Surgery: A Comprehensive Review, 7th ed, Philadelphia: Saunders, 2006.
