Carotid Endarterectomy - Indications

Indications

The aim of CEA is to prevent the adverse sequelae of carotid artery stenosis secondary to atherosclerotic disease, i.e. ischemic 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 CEA risks for combined 30 day mortality and stroke risk should be < 3% for asymptomatic patients and ≤ 6% for symptomatic patients. Symptomatic patients typically have either transient ischemic attack (TIA) or minor stroke, defined as a focal neurologic defect affecting one side of the body, speech, or vision. Asymptomatic patients have narrowing of their carotid arteries, but have not experienced a TIA or stroke.

Carotid stenosis is diagnosed with ultrasound doppler studies of the neck arteries, magnetic resonance angiography (MRA) or computed tomography angiography (CTA) or invasive angiography. Revascularization of symptomatic stenoses has a much higher therapeutic index compared to asymptomatic lesions.

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 in symptomatic patients. 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 ) / ( poststenotic diameter ) ) × 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 rate and hence benefit less from the procedure. For maximum benefit patients should be operated on soon after a TIA or stroke, preferably within the first 2 weeks.

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. The key in estimating the potential benefit for revascularization in asymptomatic patients is understanding the natural history of the disease, including the annual risk of stroke. Most agree that the annual risk of stroke in patients with asymptomatic carotid disease is between 1% and 2%, although some patients are considered to be at higher risk such as those with ulcerated plaques. In randomized trials of CEA compared to medication therapy, it has been shown that stroke is reduced by surgery, but the benefit does not appear for several years after the surgery is performed. This is because there are peri-operative complications (stroke and death) in the surgical patients. The longer a patient lives after surgery magnifies the surgical benefit. Typically, asymptomatic patients must be expected to survive at least 5 years after surgery to warrant accepting the risk of surgery. Current surgical best-practice restricts surgery for asymptomatic carotid stenosis to patients with ≥80% carotid stenosis if the surgery can be performed with ≤3% risk of 30 day stroke and death.