Carotid Endarterectomy

Stroke is diagnosed one half million times each year and consumes a tremendous amount of medical resources. It is rare in medicine that a surgical procedure, such as carotid endarterectomy, is subjected to rigorous scientific study of its efficacy. In this instance, does removal of a stenosis in a carotid artery reduce the incidence of stroke? In the early 1990's several well-designed studies clearly demonstrated the advantage of carotid endarterectomy over medical therapy in selected patients. Success of this surgery depends not only on patient selection but surgeon selection since the advantage of surgery is present only if the surgeon has a low incidence of complications such as stroke.

Arteries become narrowed (stenosis) by the formation of a plaque. The plaque is composed of fatty material and occasionally contains calcium. It is sometimes coated with small pieces of clot. For some unknown reason a common place for a stenosis to occur is at the point where the internal carotid artery branches from the common carotid artery. When a plaque narrows the vessel lumen (inside of the vessel) by 60-70%, the chance of a major stroke is statistically less with surgery than with medication. The chance of a major stroke is also greater if the patient has had a previous small stroke than if he has not had a small stroke. The stroke may occur because:
• the stenosis in the artery limits the flow of blood to the brain
• a blood clot forms in a brain artery (thrombosis)
• a small piece of blood clot or plaque breaks off and lodges in one of the arteries in the brain (embolus) When an artery to a part of the brain is blocked
• the region that the artery feeds dies (an infarct)

This produces the symptoms of a stroke (Figure 2a, 2b). A hemorrhagic stroke occurs when there is also bleeding into the brain.

Signs and Symtoms of a Stroke

A patient may or may not have symptoms of a small stroke (transient ischemic attack, TIA or mini-stroke). The symptoms of a TIA include:
• Sudden numbness or weakness of the face, arm or leg on one side of the body
• Loss of speech
• Trouble talking or trouble understanding speech
• Sudden dimness or loss of vision in one eye

Additional symptoms that may represent a stroke are:
• Unexplained dizziness
• Unsteadiness, or fall
• Severe, unexplained headache
• Double vision
• Drowsiness
• Nausea and vomiting

An individual having the above symptoms should immediately go to the nearest hospital emergency room that is able to treat a stroke or call 911. If seen in the emergency room within three hours, medication that dissolves the blood clot in the blocked artery can be given and the stroke reversed.

Indications:

There are various risk factors that heighten the incidence of stroke. They are:
• Increased age
• Male
• African-American
• Family history of stroke
• Diabetes mellitus
• High blood cholesterol
• Obesity
• Inactivity
• High blood pressure
• Smoking
• Heart disease
• Radiation therapy to the neck

On examination your doctor using a stethoscope may hear a bruit (swishing sound synchronous with the heart pulse) over the carotid artery. The bruit usually means that there is a significant stenosis of the carotid artery. When there are no associated symptoms, this is designated as an asymptomatic carotid stenosis. The stenosis is designated as symptomatic when associated with symptoms of small stroke:
• There may be weakness of one side of the body (the side opposite the stenosis)
• Speech may be garbled or not understood
• There may be a loss of vision in one eye
• The blood vessels of the retina of the eye may show tiny spots that are very small emboli
• There may be confusion and difficulty in recalling recent events

Preoperative Evaluation:

Doppler/Duplex Ultrasound: A sensor connected to a special computer and monitor is placed over the carotid artery in the neck and images the flow of blood in the artery. The presence and approximate degree of stenosis can be determined. Angiography: A catheter introduced into the femoral artery in the groin is passed upwards through the aorta and then under fluoroscopic control into each common carotid artery. A dye that shows up on X-ray is injected through the catheter. Serial X-ray films or angiograms are then obtained of the carotid artery circulation. Review of the films demonstrates whether a stenosis is present and the degree of the stenosis An ulcer in the wall of the artery may also be found. Furthermore, examination of the remainder of the circulation may show a second point of narrowing or the occlusion of a vessel in the brain. The review will also help your surgeon in planning future surgery. Computerized Tomography (CT) and Magnetic Resonance Imaging (MRI): Both these exams produce images of the brain which may demonstrate evidence of present or past strokes or evidence of a blood clot. CT or MRI Angiography: These are special types of CT and MRI that produce angiograms without the passing a catheter. These tests are more accurate than Duplex Ultrasound but not as accurate as the standard angiograms.

Who should be selected for surgery? This at times can be a difficult question for your surgeon to answer. Some indications are listed:
• Surgery is most appropriate in a symptomatic patient with greater than a 70% carotid artery stenosis
• Surgery is appropriate in a symptomatic or asymptomatic patient with greater than 60% stenosis, particularly if the plaque is ulcerated
• The patient remains symptomatic on aspirin
• The opposite carotid artery is blocked
• The degree of stenosis is greater, particularly if serial studies demonstrate progressive narrowing
• Evidence on CT or MRI of a small stroke that did not produce symptoms
• The patient is relatively young

Surgery is not appropriate when:
• The stenosis is less than 50% in a symptomatic patient
• The stenosis is less than 60% in an asymptomatic patient
• The patient has a recent large area of dead brain on studies
• The patient is in poor medical condition
• The surgeon's surgical incidence of stroke or death is greater than 3%

Procedure:

The procedure may be carried out with the patient asleep under general anesthesia or awake under local anesthesia depending on the preference of the surgeon.
• An incision is made in the neck.
• The dissection is carried down to the carotid artery.
• Care is taken to not injure the jugular vein, vagus nerve (to the heart and bowel), the hypoglossal nerve (to the tongue), and the recurrent laryngeal nerve (to the vocal cords).
• The common, external and internal carotid arteries are separated from the surrounding tissues.
• Heparin, a blood thinner, is injected to prevent blood clotting during surgery on the vessels. An elevated blood pressure is maintained to improve the flow of blood through other vessels going to the brain.
• The three carotid arteries are clamped with special vascular clamps and the status of the patient monitored . The carotid arteries are dissected from the surrounding tissues and clamps applied.
• The common carotid artery is opened below the plaque and carried upward into the internal carotid artery
Some surgeons:
• always place a shunt between the common carotid artery below the plaque and the internal carotid artery above the plaque
• place a shunt only when monitoring indicates an inadequate amount of blood is getting to the brain
• always insert a patch graft into the vessel to make it wider while others only insert a patch graft when they believe it is necessary
• The incision is closed after a drain is inserted to drain away blood that may accumulate in the wound

Complications:

• A major complication of this procedure is a stroke, just the medical problem that the patient is trying to avoid by having the surgery. The stroke may be minor or major and can lead to death
• Death is usually due to a heart attack because many of the patients having a carotid endarterectomy also have:
• Significant coronary artery disease
• Blood clot in the neck
• Injury to various nerves in the neck:
• Hypoglossal nerve - weakness of the tongue
• Vagus nerve - may effect the heart or bowel
• Facial nerve - weakness of the face
• Accessory nerve- weakness in turning the head to the opposite
side due to weakness of the sternomastoid muscle
• Recurrent laryngeal nerve- vocal cord paralysis
• Infection


Recovery:

After surgery, the patient is closely monitored for any change in level of consciousness and for excessively high or low blood pressure. The drain is removed and the patient may be discharged on the first post-operative day if there are no medical or surgical problems. A change in life style reduces the risk of further problems in the arteries:
• Stop smoking
• Begin a low fat diet
• Check blood cholesterol at least twice per year
• Control diabetes and high blood pressure
• Have a regular exercise program
• Follow up with your doctor at regular intervals