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
-
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 or branching showing widely patent
arteries. However note the mild degree of wall thickening in
this exceptional image.
Figure 2 The internal carotid artery, which is
the main blood supply to the brain, is 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 narroing in the artery.
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 -
Patients with disease can dramatically lessen the
likelihood of the narrowing becoming worse. Most
importantly, stop smoking! This is the #1 bad
thing you do for your arteries. Make sure to exercise
regularly, control blood pressure, blood sugar, and
cholesterol levels, and maintain proper weight and
diet.
-
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. The schedule that
is best for you depends upon the initial severity and
you and your physician's preference.
-
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. Your physician will decide if this may be
right for you.
-
Surgery - Studies
indicate that patients with symptoms or with a severe
narrowing may benefit from surgery to remove the plaque
buildup. While this surgery does carry risk of
complications (just like any surgery) it 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
Diagram of a Guidant "Acculink" carotid stent with
a device to catch any pieces that could break loose during
the procedure.
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