Introduction
Carotid Endarterectomy is a surgical procedure to remove atherosclerotic plaque from the carotid arteries to prevent a stroke.
A stroke can be a severe disabling or fatal event. Stenosis (narrowing) of the carotid arteries is a common cause of stroke. The narrowing is due to a buildup of plaque within the carotid artery. As more plaque develops, it can become soft and friable, with plaque and clotted blood being dislodged and travelling up to the Brain. This material can block the small arteries in the Brain, cause damage to the Brain tissue, and subsequently the symptoms of a stroke. The amount of damage and the part of the Brain affected will determine the type of symptoms and the amount of recovery.
Indications
Carotid Endarterectomy is performed to treat a narrowing (Stenosis) of the carotid artery. The aim of the surgery is to prevent a stroke from developing. There are 2 main indications for the surgery:
- Patients having symptoms from the carotid stenosis.
- Stroke – arm or leg weakness, facial droop, speech difficulties.
- Transient Ischaemic Attack – the same symptoms of stroke but recovering in <24 hours.
- Visual Loss (Amaurosis Fugax) – the temporary or permanent loss of vision form the eye on the same side as the stenosis.
- Asymptomatic (No Symptoms) Severe Stenosis.
There is significant work-up to determine which patients would benefit from carotid surgery. Carotid Endarterectomy is a very effective operation; however, it can cause some cardiac stress and there is a small risk of stroke form the surgery. The benefits vs risks need to be evaluated very carefully before deciding on surgery.
For most patients with Symptomatic disease, carotid surgery is recommended as there is a high risk of recurrent events and the potential for more disabling symptoms. In some situations, if the risk of surgery is high due to other medical issues, then optimisation of medications and extra blood thinners may be recommended.
In asymptomatic patients, the benefit of carotid surgery is not as well defined. Generally, surgery is recommended in patients who are considered a low risk of surgery, with minimal other medical issues, and a severe narrowing or stenosis. In lesser degrees of stenosis, medical treatment and surveillance is recommended.
Preoperative Instructions
Ultrasound scans are usually the first line investigation in assessing the degree of carotid arterial narrowing. A CT angiogram is performed when planning surgery or to assess the nature of the atherosclerotic plaque causing the narrowing. A review of other medical issue is performed to assess fitness for surgery. This may include a cardiac stress test.
Most patients will be admitted the day prior to surgery to review medications and ensure that the blood pressure is in a normal range. It is important to avoid surgery if the blood pressure is too high or too low. It is helpful to bring a list of current medications into the hospital. Blood thinning and diabetic medications in particular need reviewing prior to surgery.
Procedure
The surgery is performed under general anaesthesia. Several catheters will be inserted by the anaesthetist to allow monitoring during the operation. Careful blood pressure control is critical throughout the operation and the post-operative period.
During the operation, the carotid vessels are exposed though an incision on the side of the neck. Several important nerves are carefully separated from the artery. Once the artery is exposed, strong blood thinners are administered. The arteries are then clamped to stop the blood flow. The artery is then opened along its length at the site of the plaque. To maintain blood flow to the brain during the operation, a small tube (Shunt) is inserted to allow blood flow whilst the plaque is removed. Most patients do not require a shunt and the need is assessed at the time of surgery.
The plaque that causes the narrowing builds up on the inner part of the artery wall. This can be scraped away leaving a smooth surface. The remaining artery is quite strong and is closed with an artificial patch that increases the size of the artery, makes it easier to suture and reduces the risk of further narrowing developing.
The surgical wound is then closed with a dissolving suture that will not require removal. A drainage tube is placed in the wound to minimize the risk of swelling in the neck.
Routine monitoring is then performed in the Intensive Care Unit, to monitor Blood Pressure and Neurological observations closely.
Postoperative Instructions
Most patients will be transferred to the surgical ward from intensive care on the day following surgery. The drain and most of the monitoring catheters will be removed.
Once on the ward, returning to normal mobilization is encouraged with assistance from the Physiotherapist as required. Ongoing blood pressure monitoring is performed.
Discharge home will usually occur on the 2-3 post operative day. Some patients may require further rehabilitation if they have suffered from a stroke prior to their surgery.
Follow-up appointments will occur at 2 weeks and then 6 weeks with an Ultrasound scan. Routine annual surveillance will then be performed to monitor the surgical site and carotid artery on the other side.
Risks
Whilst very effective at removing the carotid plaque, carotid surgery does have a number of potentially very serious complications. These include:
- Bleeding – the carotid arteries are large and there is the potential of bleeding from any vascular procedure. If significant bleeding did occur then urgent re-operation would be required.
- Infection
- Stoke – the aim of surgery is to prevent stroke. There is a small risk of stroke from carotid surgery. This may occur due to clamping the arteries, dislodging plaque during exposure or due to clot formation on the treated artery. Stroke following surgery can be very minor with full recovery or a severe disabling stroke. Symptoms can include arm or leg weakness, speech difficulty or visual loss. In severe cases there is a risk of life-threatening damage.
- Nerve injury – numbness along the jaw line will occur. This will generally improve over several months. The vagus nerve is very close to the artery and damage can cause hoarseness of the voice. It will generally improve with time but in rare situations can be permanent. The hypoglossal nerve is close to the carotid vessels and damage can produce difficulty with speech and swallowing. This usually resolves with time.
- Cardiac Complications – carotid surgery can cause fluctuations of blood pressure This in turn can cause some cardiac stress with the risk of a heart attack developing.
- Intra-cranial Haemorrhage – this is a very rare complication and can develop if the blood pressure is too high. Removing the plaque does increase the blood flow to the brain tissue on that side which can pose a risk of bleeding, particularly if a previous large stroke has occurred.
- Re-Narrowing – whilst uncommon, it is possible that the treated artery can re-narrow over time. This can be due to more plaque development or due to scarring at the site of the surgery. Most re-narrowing is treated with medications, however re-operation may be required.
Treatment Alternatives
Medical treatment is the main alternative to carotid surgery. The use of blood thinners and cholesterol medications to stabilize the plaque is indicated in lower degrees of stenosis or if severe other medical issues increase the risk of surgery. These treatments are always instigated even if surgery is recommended.
Carotid stenting is an alternative to surgery. Stenting causes less stress on the patient and is useful in patients with a higher risk for carotid endarterectomy. The risk of neurological complications is higher with stenting so endarterectomy is generally preferred for most patients.