Carotid
Artery Disease
Carotid
artery disease, also called carotid artery stenosis,
occurs when the carotid arteries, the main blood
vessels that carry oxygenated blood to the brain,
become narrowed. The narrowing of the carotid
arteries is most commonly related to atherosclerosis
(a build-up of plaque, which is a deposit of fatty
substances, cholesterol, cellular waste products,
calcium, and fibrin in the inner lining of an
artery). Atherosclerosis, or "hardening of
the arteries," is a vascular disease (disease
of the arteries and veins). Carotid artery disease
is similar to coronary artery disease, in which
blockages occur in the arteries of the heart,
and may cause a heart attack.
To better
understand how carotid artery disease affects
the brain, a basic review of the anatomy of the
circulation system of the brain follows.
What are the
carotid arteries?
The
main supply of blood to the brain is carried by
the carotid arteries. The carotid arteries branch
off from the aorta (the largest artery in the
body) a short distance from the heart, and extend
upward through the neck carrying oxygen-rich blood
to the brain.
There
are four carotid arteries: the right and left
internal carotid arteries and the right and left
external carotid arteries. One pair (external
and internal) is located on each side of the neck.
Just as a pulse can be felt in the wrists, a pulse
can also be felt on either side of the neck over
the carotid arteries.
Because
the carotid arteries deliver blood to the brain,
carotid artery disease can have serious implications
by reducing the flow of oxygen and nutrients to
the brain. The brain needs a constant supply of
oxygen and nutrients in order to function. Even
a brief interruption in blood supply can cause
problems. Brain cells begin to die after just
a few minutes without blood or oxygen. If the
narrowing of the carotid arteries becomes severe
enough to block blood flow, or a piece of atherosclerotic
plaque breaks off and obstructs blood flow to
the brain, a stroke may occur.
Atherosclerosis
is the most common cause of carotid artery disease.
It is unknown exactly how atherosclerosis begins
or what causes it. Atherosclerosis is a slow,
progressive, vascular disease that may start as
early as childhood. However, the disease has the
potential to progress rapidly. It is generally
characterized by the accumulation of fatty deposits
along the innermost layer of the arteries. If
the disease process progresses, plaque formation
may take place. Plaque is made up of deposits
of smooth muscle cells, fatty substances, cholesterol,
calcium, and cellular waste products. This thickening
narrows the arteries and can decrease blood flow
or completely block the flow of blood to the brain.
Atherosclerosis
is thought to play an important role in the development
of carotid artery disease. Risk factors associated
with atherosclerosis include:
- older age
- male
- family history
- race or ethnicity
- genetic factors
- hyperlipidemia (elevated
fats in the blood)
- hypertension (high
blood pressure)
- smoking
- diabetes
- obesity
- diet high in saturated
fat
A risk
factor is anything that may increase a person's
chance of developing a disease. It may be an activity,
such as smoking, diet, family history, or many
other things. Different diseases have different
risk factors.
Although
these risk factors increase a person's risk,
they do not necessarily cause the disease. Some
people with one or more risk factors never develop
the disease, while others develop disease and
have no known risk factors. Knowing your risk
factors to any disease can help to guide you into
the appropriate actions, including changing behaviors
and being clinically monitored for the disease.
Carotid
artery disease may be asymptomatic (without symptoms)
or symptomatic (with symptoms). Asymptomatic carotid
disease is the presence of a significant amount
of atherosclerotic build-up without obstructing
enough blood flow to cause symptoms. Symptomatic
carotid artery disease may result in either a
transient ischemic attack (TIA) and/or a stroke
(brain attack).
A transient
ischemic attack is a sudden or a temporary loss
of blood flow to an area of the brain, usually
lasting less than five minutes but not longer
than 24 hours, with complete recovery. Symptoms
of a TIA may include, but are not limited to,
the following:
- sudden weakness or
clumsiness of an arm and/or leg on one side
of the body
- sudden paralysis (inability
to move) of an arm and/or leg on one side of
the body
- loss of coordination
or movement
- confusion, dizziness,
fainting, and/or headache
- numbness or loss of
sensation (feeling) in the face
- numbness or loss of
sensation in an arm and/or leg
- temporary loss of vision
or blurred vision
- inability to speak
clearly or slurred speech
TIA
may be related to severe narrowing or blockage
or from small pieces of an atherosclerotic plaque
breaking off, traveling through the bloodstream,
and lodging in small blood vessels in the brain.
With TIA, there is rarely permanent brain damage.
Call
for medical help immediately if you suspect a
person is having a TIA, as it may be a warning
sign that a stroke is about to occur. Not all
strokes, however, are preceded by TIAs.
Stroke
is another indicator of carotid artery disease.
The symptoms of a stroke are the same as for a
TIA. A stroke is loss of blood flow (ischemia)
to the brain that continues long enough to cause
permanent brain damage. Brain cells begin to die
after just a few minutes without blood or oxygen.
The area of dead cells in tissues is called an
infarct.
The
area of the brain that suffered the loss of blood
flow will determine what the physical or mental
disability may be. This may include impaired ability
with movement, speech, thinking and memory, bowel
and bladder function, eating, emotional control,
and other vital body functions. Recovery from
the specific ability affected depends on the size
and location of the stroke. A minor stroke may
result in only minor problems such as weakness
in an arm or leg. More severe strokes may cause
paralysis, loss of speech, or even death.
The
symptoms of carotid artery disease may resemble
other medical conditions or problems. Always consult
your physician for a diagnosis.
In addition
to a complete medical history and physical examination,
diagnostic procedures for carotid artery disease
may include any, or a combination, of the following:
- auscultation (listening
to) of carotid arteries - placement of a stethoscope
over the carotid artery to listen for a particular
sound called a bruit (pronounced brew-ee). A
bruit is an abnormal sound that is produced
by blood passing through a narrowed artery.
A bruit is generally considered a sign of an
atherosclerotic artery; however, an artery may
be diseased without producing this sound.
- carotid artery duplex
scan - a type of vascular ultrasound study performed
to assess the blood flow of the carotid arteries.
A carotid artery duplex scan is a noninvasive
(the skin is not pierced) procedure. A transducer
sends out ultrasonic sound waves at a frequency
too high to be heard. When the transducer (like
a microphone) is placed on the carotid arteries
at certain locations and angles, the ultrasonic
sound waves move through the skin and other
body tissues to the blood vessels, where the
waves echo off of the blood cells. The transducer
picks up the reflected waves and sends them
to an amplifier, which makes the ultrasonic
sound waves audible. Absence or faintness of
these sounds may indicate an obstruction to
the blood flow.
- magnetic resonance
imaging (MRI) - a diagnostic procedure that
uses a combination of large magnets, radiofrequencies,
and a computer to produce detailed images of
organs and structures within the body.
- magnetic resonance
angiography (MRA) - a noninvasive diagnostic
procedure that uses a combination of magnetic
resonance technology (MRI) and intravenous (IV)
contrast dye to visualize blood vessels. Contrast
dye causes blood vessels to appear opaque on
the MRI image, allowing the physician to visualize
the blood vessels being evaluated.
- computed tomography
scan (Also called a CT or CAT scan.) - a diagnostic
imaging procedure that uses a combination of
x-rays and computer technology to produce cross-sectional
images (often called slices), both horizontally
and vertically, of the body. A CT scan shows
detailed images of any part of the body, including
the bones, muscles, fat, and organs. CT scans
are more detailed than general x-rays.
- angiography - an invasive
procedure used to assess the degree of blockage
or narrowing of the carotid arteries by taking
x-ray images while a contrast dye in injected.
The contrast dye helps to visualize the shape
and flow of blood through the arteries as x-ray
images are made.
Specific
treatment for carotid artery disease will be determined
by your physician based on:
- your age, overall health,
and medical history
- extent of the disease
- your signs and symptoms
- your tolerance of specific
medications, procedures, or therapies
- expectations for the
course of the disease
- your opinion or preference
Carotid
artery disease (asymptomatic or symptomatic) in
which the narrowing of the carotid artery is less
than 50 percent is most often treated medically.
Asymptomatic disease with less than 70 percent
narrowing may also be treated medically, depending
on the individual situation.
Medical
treatment for carotid artery disease may include:
- modification of risk
factors
Risk factors that may be modified include smoking,
elevated cholesterol levels, elevated blood
glucose levels, lack of exercise, poor dietary
habits, and elevated blood pressure.
- medications-
Medications that may be used to treat carotid
artery disease include:
- antiplatelet medications
- medications used to decrease the ability
of platelets in the blood to stick together
and cause clots. Aspirin, clopidogrel (Plavix®),
ticlopidine (Ticlid®), and dipyridamole
(Persantine®) are examples of antiplatelet
medications.
- anticoagulants
- also described as "blood thinners,"
these medications work differently than
antiplatelet medications to decrease the
ability of the blood to clot. An example
of an anticoagulant is warfarin (Coumadin®).
- antihyperlipidemics
- medications used to lower lipids (fats)
in the blood, particularly cholesterol. Statins
are a group of antihyperlipidemic medications,
and include simvastatin (Zocor®), atorvastatin
(Lipitor®), and pravastatin (Pravachol®),
among others. Studies have shown that certain
statins can decrease the thickness of the
carotid artery wall and increase the size
of the lumen (opening) of the artery.
- antihypertensives
- medications used to lower blood pressure.
There are several different groups of medications
which act in different ways to lower blood
pressure.
In persons
with narrowing of the carotid artery greater than
50 percent to 69 percent, a more aggressive treatment
may be recommended, particularly in persons with
symptoms. Surgical treatment decreases the risk
for stroke after symptoms such as TIA or minor
stroke, especially in persons with an occlusion
(blockage) of more than 70 percent who are good
candidates for surgery.
Surgical
treatment of carotid artery disease includes:
- carotid endarterectomy
(CEA)
Carotid endarterectomy is a procedure used to
remove plaque and clots from the carotid arteries,
located in the neck. Endarterectomy may help
prevent a stroke from occurring, particularly
in persons with a carotid artery narrowing of
80 percent or more.
- carotid artery angioplasty
with stenting (CAS)
Carotid angioplasty with stenting is a minimally
invasive procedure in which a very small hollow
tube, or catheter, is advanced from a blood
vessel in the groin to the carotid arteries.
Once the catheter is in place, a balloon may
be inflated to open the artery and a stent is
placed. A stent is a cylinder-like tube made
of thin metal-mesh framework used to hold the
artery open. Because there is a risk of stroke
from bits of plaque breaking off during the
procedure, an apparatus, called an embolic protection
device, may be used. An embolic protection device
is a filter (like a small basket) that is attached
on a guidewire to catch any debris that may
break off during the procedure. While this procedure
is performed widely, the long-term effects are
still being studied.
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