Cartiod

Introduction

There are four major arteries that feed nutrient rich blood from the heart to the brain. Two of these arteries run along the back of the neck, are smaller in diameter, and are named the vertebrals. The larger of the arteries that feed the brain are in the front of the neck and are named the carotid arteries. The carotid arteries are often involved with atherosclerosis (hardening of the arteries) that results in narrowing of the lumen (opening) of the blood vessel and can create a rough surface for the blood to travel over.

Stroke

Discussion of carotid artery disease must begin with a basic understanding of stroke. Stroke, the third leading cause of death in the United States, should be defined as permanent injury to nerve tissues of the brain. Stroke (the medical term for stroke is Cerebro-Vascular Accident or CVA) can be a result of bleeding into the brain tissue itself, spasm of small arteries that feed nutrients to the brain, or more commonly failure of blood to reach a portion of the brain due to blocked blood vessels. The issue was confused for many years, but now a clearer understanding of how atherosclerosis (hardening of the arteries) results in stroke has been well accepted by the medical community.

Survival of a stroke can leave someone permanently disabled, with loss of function of arms, legs, facial muscles, or speech. The brain has two sides, or hemispheres, with functions assigned to different areas on each side. The ability to move and feel things is located along the outer surface of the brain on both sides. One of the interesting components of stroke is that the nerve fibers from the brain cross as they enter the spinal cord. Thus, injury to the right brain results in left body weakness or numbness, and vice versa. Symptoms of stroke include sudden loss of speech, loss of sensation, loss of movement, loss of vision, in a specific region or 'side' of the body. In general, complaints of these events occurring on both sides of the body at the same time (arms, both legs, both eyes) would not fulfil the classic 'stroke' pattern.

The most common form of stroke is ischemic in nature (not enough blood to an area of the brain for too long a period of time) and results from sudden occlusion of the branch artery that feeds blood to the outer portion of the brain. The most common artery involved with this sudden occlusion is known as the middle cerebral artery (MCA), which is the major branch of the front neck artery, called the internal carotid artery. Ischemic stroke occurs when a piece of the diseased portion of the artery 'upstream' from the brain breaks off and travels downstream to the smaller blood vessels (embolus) until it gets stuck (impacts) and stops blood from flowing to a particular portion of the brain. The diseased portion of the artery can be part of the material of atherosclerosis itself (called plaque-pronounced 'plack') or collections of small clots that form on the rough surface of the diseased artery. The main component of these small clots is often a circulating blood component known as the platelet.

Sometimes the 'clumped' platelets will impact into the MCA and result in symptoms of stroke, but just as suddenly will break up and circulation to the brain will be restored. These events when symptoms of stroke come and go quickly are called transient ischemic attacks (TIA's). These are warning signs that a major disabling stroke may be imminent. People who have a transient ischemic attack have a 10-15% chance of having a major disabling stroke within 1 year, and then a 3-5% per year chance after that. Thus, the risk of stroke in these patients can be as high as 20-25% (roughly 1 in 4) in three years with treatment by medications alone.

Since there is no way to replace or to grow brain tissue in the adult, the best treatment for stroke is prevention. Surgery on the artery, called a carotid endarterectomy, is a way of removing the blockage and the reducing the risk of crumbling plaque becoming an embolus and the rough plaque surface causing platelets to 'clump'. Medications such as aspirin can reduce the chances of stroke and are advocated for this very reason (They also reduce the risk of heart attacks for the same principles). Nevertheless, recent studies have conclusively demonstrated that medication therapy is inferior to surgery in several instances.

Carotid Endarterectomy

The surgical removal of the material inside the arteries at the front of the neck that provide blood to the brain is called a carotid endarterectomy (CEA). This procedure can be performed with the patient awake (local anesthesia) or asleep (general anesthesia). Precautions are usually taken to ensure adequate blood flow to the brain during the operation and may include; the monitoring of brain waves (EEG), keeping the patient awake for repeated examinations, monitoring 'back pressure' in the clamped artery, or placing a diverting tube to allow continued blood flow to the brain (shunt). Each method is acceptable, and choice should be determined based upon the surgeon, the patient, and the facility at which the operation is performed. The patient has an incision in the front of the neck along where the artery lies. Further description of the procedure can be found at the PVSS website at www.pvss.org in the photoatlas section.

The major risks of CEA are stroke, bleeding, heart attack, death, infection, and cranial nerve injury. CEA does prevent stroke statistically, but there is also a risk of stroke with the operation. Stroke occurs about 2% of the time when the artery is operated for the amount of blockage alone, and about 3-5% of the time when the artery is already causing problems such as transient ischemic attacks (see above). This may seem strange that the operation causes the very thing it is trying to prevent, but it is one of the unavoidable possibilities of this operation. The risk of heart attack is real for many of the patients undergoing CEA. The risk of heart attack is not so much from the stress of the operation, as it is having blockages in your carotid arteries is a risk for having disease in the arteries that feed the heart. The incidence of significant bleeding and infection are actually small. Cranial nerves are nerves that control such things as the tongue, the voice box, the face, and swallowing. These nerves can be injured with operation, usually a 'stretch' injury. The vast majority of these nerve injuries are partial, not disabling, and fortunately temporary. There are some superficial nerves that can (and sometimes must) be severed to complete the operation. These superficial nerves provide 'feeling' to the ear and neck. Patients comment after the operation of numbness or a strange feeling (especially men who shave), but it is very rare for this to be more than minor problem.

The benefit of CEA has been established in two major United States trials in the last 15 years. These trails were established because of the belief by many doctors that aspirin and drugs were superior in the prevention of stroke to surgical operation. These beliefs were put to the test in a randomized, prospective, blinded, multi-center trails (this represents the best form of medical evidence) in both the United States and Europe. The studies results in Europe and the United States had similar findings, in that surgery significantly reduced the risk of stroke compared to medication therapy in certain instances. The risk of stroke and death in three years on medication for a patient having symptoms from the involved carotid artery was 22%, and only 12.3% if surgery was performed (about half that of medication alone). When the carotid artery was blocked by more than 60% even if not causing the patient any problems, the risk of stroke in five years with medications was 11%, and only about 5% with surgery.

Frequently Asked Questions: FAQ's

1. My physician had me go for a test that they ran a probe over my neck. What is that and what is it for?

Answer: The most common test used to find blockages in the arteries of the neck is an ultrasound study called a carotid duplex. The study involves having the patient lay still while sound waves are used to make pictures of the artery and find how tight the blockages in the artery are. The test is not painful, can be accurate if in well trained hands. Your physician may have heard an abnormal sound (bruit) while listening to your neck and may have been concerned that it was caused by turbulent (uneven) blood blow that occurs when a blockage in the artery is present.

2. I have a blockage in my artery of the neck and have been told that I would do better with an operation. Who should do the surgery?

Answer: The training, experience, and number of similar operations performed by a surgeon, as well as the facility, have been implicated in publications as affecting the results of the operation. Vascular surgeons are general surgeons with extended training in the diagnosis, treatment, and operative intervention of vascular diseases, including carotid diseases. Finding a board certified/board eligible (BC/BE) peripheral vascular surgeon will establish that specialized training in this area has occurred. The understanding of 'specialists' in this are can be confusing. Currently the following types of surgeons may perform carotid endarterectomy: Neurosurgeons, Cardiac Surgeons, General Surgeons, and Vascular Surgeons, any of which may or may not be board certified/board eligible in their specialty. The United States studies that established the safety record for CEA were based in institutions were many operations were performed, mostly by BE/BC Vascular Surgeons, but on instances other specialists with high volume of this surgery were included. The finding of 'results' and comparing them to expectations for hospitals and surgeons can be difficult. Reasonably, a trained and experienced surgeon, performing at least 25 CEAs a year, who has some verification of results, should be available in your area and provide a safe operation.

3. I had my artery operated on and they keep sending me to get more ultrasounds. Why? 

Answer: In a small number of patients, the artery makes to much scar tissue (intimal hyperplasia) as it heals and this blocks up the artery again. Fortunately, these scar blockages (re-stenosis) do not often require another operation. Another good reason to get the ultrasounds is to monitor the artery that was not operated on, which in fact is more likely to require subsequent operation.

4. Why can't you put up a balloon in the artery and open it up like they did in my heart? 

Answer: Carotid balloon angioplasty (balloon in the artery) is in fact a reality, it must be considered experimental! This procedure is done usually from a groin puncture using a local anesthetic. The risk of cranial nerve injury is very low, as is the risk of infection and bleeding. However, the risk of stroke with Carotid Angioplasty is not well established but appears to be somewhere in the range of 8-12+% (compared to 1.8% for CEA for asymptomatic disease and 3-5% for symptomatic disease). There are many physicians now, most not surgeons, performing carotid angioplasty. The results seem to vary from publication to publication and generally do not contain good controls. While published reports for carotid angioplasty have dotted the literature for more than 5 years, and numerous physicians untrained in the medical treatment of peripheral vascular diseases are performing them, there has been no prospective trail to compare the results to standard surgery yet.

The surgical trails for carotid surgery for blockages demonstrated that a low operative risk was necessary to have statistical reduction in risk of stroke. Thus, if the operation can not be done with a low risk of stroke (<3-4% risk) it should NOT be performed as it would be of no 'statistical' benefit to patients. It is ludicrous to justify a procedure (carotid angioplasty) with an 8-12% immediate risk and completely unknown later risks, when the risk of the artery causing a stroke is only 11% in 5 years! Therefore, your five-year risk of stroke with carotid balloon angioplasty could very well be MUCH HIGHER than if you were to have just left it alone. Based upon current evidence, it is strongly suggested that consultation with a BE/BC peripheral vascular surgeon to discuss treatment options and to ensure that "informed consent" have been achieved prior to signing any consent for carotid balloon angioplasty. The issues of risk reduction, operative and procedure risks, natural history, and understanding of the national and international trials, are complex and someone with documented specialty training in vascular diseases can make a significant impact on your, as well as families, potential future quality of life. This is not to say that carotid balloon angioplasty should never be performed, but to ensure that the person who undergoes the risk of stroke well understands the risks and benefits (informed consent) of all treatment options.

5. How does my brain get blood while your operating on it?

There are several blood vessels capable of bringing blood to the brain while the operated artery is clamped for repair. The majority of patients (nearly 75% or more) will have adequate blood flow even with one carotid artery clamped to prevent injury. Understanding that the rough surface of the disease inside the artery is causing embolus to travel downstream and block up a small channel rather than a problem with the flow itself explains why the majority of patients can have one artery safely clamped during the time for the operation. The brain can receive blood temporarily via a shunt (a plastic tube placed into the artery above and below that plaque) should it become necessary.

We at the PVSS hopes this information as answered what may be some of your questions about carotid artery blockage and surgery.

Sincerely,

Peter S. Dovgan, M.D. for the PVSS

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