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Carotid endarterectomy
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Carotid endarterectomy (CEA) is a surgical procedure used to prevent stroke, by correcting stenosis in the 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.
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Carotid endarterectomy (CEA) is a surgical procedure used to prevent stroke, by correcting stenosis in the 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.
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. Surgeons are divided over whether asymptomatic patients should be treated with medication alone or should have surgery.
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. Although the guidelines describe carotid artery stenting as experimental and recommend that it be used only in clinical trials, many doctors perform this procedure outside of trials. In the early trials, carotid artery stenting caused more strokes and deaths than carotid endarterectomy, and the trials were stopped. More recently, the SAPPHIRE trial concluded that carotid artery stenting was not inferior to carotid endarterectomy after 3 years. However, Cambria concluded that the study was not sufficiently powered to detect differences in stroke and death, and final conclusions must await larger trials.Other trials are underway
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 shunt 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. 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.
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. 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 arteriography (MRA) or computerized tomographic angiography (CTA). The circle of Willis typically provides a collateral blood supply. Symptoms have to affect the other side of the body; if they do not, they may not be caused by the stenosis, in which case endarterectomy will be of minimal benefit.
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:
- percent stenosis = (1- (minimal diameter)/(post-stenotic 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 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 the either 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.
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