Carotid endarterectomy

Carotid endarterectomy (CEA) is a surgical procedure used to correct carotid stenosis (narrowing of the carotid artery lumen by atheroma), used particularly when this causes medical problems, such as transient ischemic attacks (TIAs) or cerebrovascular accidents (CVAs, strokes). Endarterectomy is the removal of material on the inside (end-) of an artery. Angioplasty and stenting of the carotid artery are undergoing investigation as alternatives to carotid endarterectomy.

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 or without a wire-mesh shunt. The safety and effectiveness of these procedures is controversial. 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. However, Cambria concluded that the study was not sufficiently powered to detect differences in stroke and death, and final conclusions must await larger trials.

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 or magnetic resonance arteriography (MRA). 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. 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 (greater than 75%). 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 patients will suffer neurological complications as a result of the procedure. Hemorrhage of the wound bed 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.