Carotid endarterectomy - When carotid endarterectomy is needed

A carotid endarterectomy may be needed if one or both of your carotid arteries become narrowed because of a build-up of fatty deposits (plaque).

This is known as carotid artery disease or carotid artery stenosis, and it significantly increases your risk of having a stroke or a transient ischaemic attack (TIA).

Why carotid artery disease develops

Normal healthy arteries are elastic and smooth on the inside, allowing blood to easily flow through them. As a person gets older, plaque can build up inside the arteries, making them narrower and stiffer. This process is called atherosclerosis.

As well as ageing, there are several other factors that can contribute to a build-up of plaque, including:

• a high-fat diet
• high blood pressure (hypertension) 
• diabetes – a lifelong condition that causes a person's blood sugar level to become too high
• smoking

Read more about the causes of atherosclerosis.

Carotid artery disease and stroke

There are two ways that a stroke or TIA could occur if the flow of blood through your carotid arteries becomes blocked or restricted. These are described below:

• if the carotid artery is completely blocked, limiting the blood supply to your brain – this type of stroke is known as an ischaemic stroke
• if a blood clot forms on the roughened surface of the carotid artery and breaks off it may block one or more arteries in the brain – this type of stroke is known as an embolic stroke

Diagnosing carotid artery disease

Carotid artery disease is usually diagnosed if a person has the symptoms of a stroke or TIA, such as the face drooping on one side, numbness or weakness in the arms or legs, speech problems or loss of vision in one eye.

However, occasionally narrowing of the carotid arteries may be diagnosed if you are having tests for another reason and the doctor testing you notices that your arteries are narrowed. This is called an asymptomatic carotid stenosis.

If you have recently had a stroke or a TIA, you will be referred for some brain imaging tests. This will allow the blood supply to your brain to be checked and any narrowing in your carotid arteries to be diagnosed.

Several tests can be used to examine your carotid arteries and find out how much plaque has built up inside them. These include:

• duplex ultrasound scan – sound waves are used to produce an image of your blood vessels and measure the blood flow through them; it can also show how narrow your blood vessels are
• computerised tomography (CT) scan – a series of X-rays are taken at slightly different angles, and a computer assembles the images to create a detailed picture of the inside of your body
• computed tomographic angiogram (CTA) – a special dye is injected into a vein and a CT machine is used to take X-rays to build up a picture of your neck arteries
• magnetic resonance angiography (MRA) – a magnetic field and radio waves are used to produce images of your arteries and the blood flow within them

An ultrasound scan is usually used first to check if there is any narrowing in your arteries and to determine whether it is severe enough for you to benefit from having surgery.

If your arteries are narrowed, you may need to have further tests to confirm the diagnosis, such as a CTA or MRA.

Grading narrowed arteries

If tests indicate that your carotid arteries are narrowed, the severity of the narrowing (stenosis) will be graded to determine if you need surgery.

In the UK, the most common grading system used is the North American Symptomatic Carotid Endarterectomy Trial (NASCET) scale. The scale has three categories:

• minor – 0-49% narrowed
• moderate – 50-69% narrowed
• severe – 70-99% blocked

When surgery is recommended

The National Institute for Health and Care Excellence (NICE) recommends that people who have had a stroke or TIA and have severe stenosis should have a carotid endarterectomy.

You should be assessed within a week of the start of your stroke or TIA symptoms, and the operation will ideally be carried out within two weeks of the start of your symptoms.

It is crucial that you seek medical advice as soon as possible if you develop symptoms of a stroke or TIA. Surgery has the best chance of preventing a further stroke if it is performed as soon as possible.

Surgery will sometimes be recommended if you have not previously had a stroke or a TIA, but you are found to have severe stenosis.

Surgery will not be recommended if you have minor stenosis (less than 50%). This is because surgery has the most benefit for people with moderate and severe stenosis (more than 50%), with the maximum benefit being seen in those with severe stenosis (70-99%).

A carotid endarterectomy is not of any benefit in people with a complete blockage of their carotid artery.