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.