Carotid Artery Disease

Carotid artery disease is the most common cause of stroke in the USA and early detection with accurate assessment is the key to prevention.

How does the cerebrovascular system work? - Blood leaves the heart via the aorta and into the common carotid arteries (CCA) on each side of the neck. About half way up the neck, this artery branches into the external carotid (ECA) that supplies the face and scalp, and the  internal carotid artery (ICA) that supplies the brain and the eye. The split or bifurcation  is a common area for disease to occur. The vertebral  arteries branch off the subclavian arteries, course along the spinal cord and supply the back of the brain. These 4 vessels make up the primary blood supply to the brain and these can be easily evaluated by noninvasive methods.

Atherosclerosis, commonly known as hardening  of the arteries, is responsible for the majority of problems in the carotid arteries. Normally the inner wall of an artery called the  intima   is smooth and elastic, allowing blood to flow freely. In vessels affected by atherosclerosis, the intima   becomes thickened and rough by a build up cholesterol or fatty materials. This build up, much like rust in a pipe, is called plaque. As this plaque increases, it obstructs the opening or lumen   of the blood vessel and may alter or limit the flow of blood. If the artery is severely narrowed, the amount of blood getting past can be so limited, that various symptoms can result. However, as long as this is a gradual process, the body is often very good at developing alternative pathways for blood flow called collaterals.   As the artery narrows, the same amount of blood wants to get through so it has to speed up, much like a “kink” in a garden hose. This fast, turbulent blood flow can break down the surface of the plaque and cause pieces of plaque called emboli   to break loose. These can travel to the brain or the eye often with dire consequences. Turbulent blood flow can produce a sound called a bruit   that can be heard with a stethoscope and is often the first sign of disease.

Diagrams of increasing build-up of deposits within the artery wall, gradually bulging the inner layer of the artery wall into the lumen or opening inside the vessel resulting in a restriction of the blood flow. Small plaques that do not result in flow disturbances are unlikely to cause symptoms. In contrast, narrowings that limit the blood flow cause increased blood velocities and turbulent flow (like a kink in a garden hose.) This results in stresses on the inside layer of the vessel. If this lining breaks down, particles called emboli are carried to the brain and can result in a stroke.

Symptoms -

Lack of blood flow to the brain can cause a variety of symptoms. Stroke (cerebrovascular accident or CVA) occurs when there is permanent damage to the brain. If blood flow is restored quickly, symptoms may resolve (Transient Ischemic Attack or TIA). There are several “classical” warning signs that should alert a person to seek immediate medical attention.

• Numbness, weakness or paralysis on one side of the body 
• Sudden temporary loss of vision in one eye or sudden blurred or double vision 
• Difficulty speaking, garbled speech, unable to use or undersstand common words 
• Loss of balance, equilibrium or falling for no apparent reason 

Diagnosis is most often made with ultrasound, a relatively inexpensive, completely safe and non-invasive technique that obtains pictures of the vessels and information about the blood flow. Plaque characteristics such as surface irregularities coupled with information about the blood flow allow an assessment of the risk a specific plaque presents to the patient. We are also able to evaluate the intracranial vessels for stenosis, arteriovenous malformation or vasospasm of the vessels within the skull. Traditionally, this information has only been obtainable by contrast angiography. Symptomatic patients without other explanation may benefit from this noninvasive test.

Figure 1                                          Figure 2

Figure 1 An ultrasound of the carotid artery bifurcation showing widely patent arteries. However note the mild degree of wall thickening in this exceptional image.

Figure 2 The internal carotid artery shown with gray scale and color Doppler. The red demonstrates blood flow to the brain while the blue is flow in the jugular vein. 

                     Figure 3                                             Figure 4

Figure 3 - The internal carotid artery showing a large plaque along the back wall of the artery

Figure 4 - This image of a carotid bifurcation uses a different Doppler processing the demonstrates the opening of the vessel extremely well. Note the "divot" which may represent an ulcer in the plaque.

                     Figure 5                                             Figure 6

The above images show a color Doppler image of an internal carotid artery with a severe stenosis. Figure 6 shows the spectral analysis which is a detailed analysis of the blood flow showing a high velocity flow pattern due to the narrowing in the artery.    

                   Figure 7                                              Figure 8

Figure 7 - Shows a common carotid artery with a dual streamline with faster flows along the walls of the vessel somewhat in contrast to typical assumption that the fastest flow is down the center of the vessel.  

Figure 8 - Another common carotid artery showing irregular palque with associated disturbance and flow eddies.

Treatments - 

Most patients with carotid artery disease do not have symptoms and are treated very conservatively without any intervention. But what else can be done??

• Modify risk factors - Smoking cessation, control of hypertension & diabetes, regular exercise

• Follow-up - Unfortunately, progression or worsening of disease does sometime occur even with modification of the risk factors and it is impossible to tell how quickly this may happen. Therefore, it is critically important that the severity of the plaque buildup be followed every 6 or 12 months by ultrasound testing to determine if there is any progression of disease.

• Medicine - While medicine will not generally lessen the plaque, there are several medications that may be prescribed to aid in controlling risk factors or to reduce the risk of symptoms.

• Surgery - Studies indicate that patients with symptoms and / or with a severe narrowing (greater than 75%) may benefit from surgery to remove the plaque buildup. Carotid endarterectomy has been done for many years and has been proven to reduce the risk of stroke in some patients with carotid artery disease.

• Angioplasty / Stenting - Called an endovascular procedure, this new technique uses a catheter inserted through the groin to open the artery and deploy a stent to hold it open. For the past several years, carotid artery stenting was only done in certain situations as it carried a slightly higher risk of stroke than the surgical procedure. However with newer devices such as those that employ an embolic protection device pictured below, the use and safety of this approach has increased significantly. For more information about stenting, click All About Stents!

Diagram of a Guidant "Acculink" carotid stent with a device to catch any pieces that could break loose during the procedure.