Download Carotid Stenosis, Transient Ischemic Attacks, and Strokes

Carotid Stenosis, Transient Ischemic
Attacks, and Strokes
Brian Dobecki
Prof. Gary Zimmerman
RDSC 326
February 22, 2006
Carotid Stenosis
The narrowing or constriction of
the carotid artery as a result of
disease.
Transient Ischemic Attacks or TIA
A "mini-stroke" caused by temporary
disturbance of blood supply to an area of the
brain, resulting in a sudden, brief decrease in
brain function. When the symptoms resolve
completely in less than 24 hours, typically
under one hour, it is called a TIA.
Stroke
Blockage or hemorrhage of a blood vessel supplying
the brain, causing inadequate oxygen supply,
resulting in such symptoms as weakness, paralysis,
speech difficulties, and if severe, loss of
consciousness or death. If the symptoms do not
resolve in under 24 hours, the event is called a
stroke. If the blood flow is not restored the brain cells
die and permanent brain damage results, resulting in
disability or death.
A Description of a Carotid Stenosis
The carotid arteries run up the sides of the neck, and
are a vital route of blood to the anterior part of the
brain and, via branches, to the eyes, forehead, and
nose. When fatty and inflammatory tissue builds up
on the inside surface of an artery, it forms a plaque.
Platelets, fibrin and other blood products can stick to
this as part of a clot or Thrombus. This leads to
some degree of blockage of flow through the artery,
plaque formation can become so severe that an
artery is effectively blocked.
Demographics
Carotid artery stenosis, or CAS, is widespread and
represents a significant public health problem.
Stroke is the third leading cause of death in the
United States after coronary artery disease and
cancer, with approximately 750,000 strokes and
more than 150,000 deaths occurring each year in the
Unites States costing an estimated $40 Billion
annually. One half of all strokes are believed to be
the result of atherosclerotic plaque/disease found in
the carotid artery.
Risk Factors
There are many risk factors associated with carotid
stenosis. First is age, the older you are the higher
the risk. High levels of cholesterol, LDL's, accelerate
development. Diabetes or high blood sugar is a
contributing factor. A sedentary lifestyle, smoking
and obesity also increase the risk of high blood
pressure as well as the development of
atherosclerosis. High blood pressure should be
treated and maintained below 140/90. So with the
exception of age, all of the other risk factors are
within our control.
Symptoms
Symptoms of TIA are the same as those that occur in
stroke and include the sudden development of:
numbness, tingling, changes in sensation such as
vertigo. Speech difficulty expressed as garbled or
slurred speech. Falling caused by weakness in the
legs, loss of balance or lack of coordination,
staggering, and heavy feeling of extremities. The
previous symptoms are a result of decreased blood
flow to the brain. Since the carotid artery also
supplies the eyes, a vision change such as
decreased or double vision, or the loss of vision in
one eye, are also symptoms of CAS.
Symptoms
Specific symptoms vary depending on the
location (which vessel is involved), the
degree of vessel involvement, and the extent
of collateral circulation. Symptoms usually
occur on the same side of the body if more
than one body part is involved. Symptoms
can also be absent, with the stenosis
discovered only incidentally during a clinical
examination.
Diagnostic Tests
Neurological, motor, and sensory examinations may
be done to determine specific neurological deficits,
because they often correspond closely to the
location of the injury to the brain. A physical
examination may be abnormal during an episode but
normal after a TIA has passed. It may also be used
to rule out a stroke in evolution rather than TIA. The
examination may show high blood pressure, emboli
in the retina, abnormal reflexes, muscle weakness,
decreased sensation or other changes.
Doppler Ultrasound
The initial screening test that is most often used in
evaluating patients is a Carotid duplex or Doppler
ultrasound.
This noninvasive test uses high frequency sound
waves to reconstruct a two dimensional image of the
carotid arteries and real time blood flow through the
arteries. The results of this test are usually given as
a range of stenosis; for example, 1% to 15%, 16% to
49%, 50% to 79%, or 80% to 99%. The blockage can
be measured and it may create a jet effect that
results in abnormally high flow velocity.
Doppler Ultrasound
This exam does have certain limitations. It
can falsely indicate a patent vessel as totally
occluded. The accuracy of the test result
depends greatly on the skill of the
sonographer.
Doppler Ultrasound
Doppler Ultrasound
assessment of blood
flow.
MRI and MRA
The second diagnostic test utilizes an MRI to
perform a magnetic resonance angiography of the
brain vessels and neck vessels. High grade
stenosis, greater than seventy percent occlusion,
may result in only a trickle of blood flow distant to the
blockage, this trickle may appear as a "string sign"
because it looks like a string of remaining flow.
However, compared with conventional cerebral
angiography, this test tents to overestimate the
degree of stenosis in the neck. It can also be
inaccurate in cases of flow turbulence or vessel
tortuosity.
MRI and MRA
However, compared with conventional
cerebral angiography, this test tents to
overestimate the degree of stenosis in the
neck. It can also be inaccurate in cases of
flow turbulence or vessel tortuosity.
MRI and MRA
High grade stenosis of
the internal carotid artery.
MRI and MRA
Motion Artifact
from swallowing.
Carotid Angiography
The third technique is Carotid Angiography.
An angiogram is an examination that utilizes
a fluoroscope after a small catheter is
inserted into the base of the carotid artery. A
contrast dye is then injected into one or both
of the carotid or vertebral arteries in the
neck. The contrast dye reveals the areas of
the regions of the artery that are narrow or
blocked.
Carotid Angiography
Digital subtraction angiography (DSI), uses a
computer to "subtract" out the bones and
tissues in the region viewed such that only
the vessels filled with contrast are seen. This
test is currently considered the gold
standard. However, no method of detection
for any disease is 100 percent accurate.
Carotid Angiography
False color carotid angiogram.
Carotid Bruit
Although not as accurate as
other methods, a physician
can listen to the pulsing of
blood through the carotid
artery by means of a
stethoscope. The weaker
pulse that is a result of
stenosis will be evident in the
form of altered sounds (Bruit),
as the blood flows past the
area of disturbance.
Treatment Options
Carotid stenosis treatment is carried out to prevent
stroke, or if a limited stroke has occurred, to prevent
further debilitating stroke. Treatment usually
requires admission to the hospital for evaluation of
the specific cause and determination of long term
treatment. Underlying disorders should be treated
appropriately, including such disorders as
hypertension, heart disease, diabetes, arteritis and
blood disorder. Treatment is carried out either
surgically or medically.
Medications
For a patient with a less than fifty percent occluded
artery, medication may be prescribed to try and
prevent a thromboembolic event. Medications
include anticholesterol or antilipid and
antihypertension agents, and antiplatelet agents
(medications which stop platelets sticking) such as
acetyl salicylic acid (ASA, Aspirin), clopidogrel
(Plavix) and ticlodipine (Ticlid) and their equivalents.
Treatment may be continued for an indefinite time
period.
Medications
Normal Circulation
Less than 50% Stenosis
Carotid Endarterectomy
Surgery should be done for those who have carotid
artery blockages which cut off between 75-99% of
blood flow. Carotid Endarterectomy is the surgical
exposure of the carotid artery and the removal of the
plaque. A surgeon makes an incision in the neck,
accesses the carotid artery, opens them and cleans
out the plaque. The vessel is then sewn closed with
or without a synthetic patch graft (one made of GoreTex or an equivalent biocompatible fabric). This
surgery is usually highly effective. This approach is
the method of choice for most patients.
Carotid Endarterectomy
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The risks of surgery usually include the risk of stroke
and the risk of a heart attack around the time of the
surgery (as most patients with carotid disease also
have some degree of coronary artery disease,
whether they know it or not). Risks of surgery also
include a small risk of infection and neck blood clots,
as well as injury to the nerves of speech, swallowing
and tongue movement.
However, Large studies have shown that for people
with such severe blockages, even if they have no
symptoms at all, the risk of stroke is reduced with
surgery.
Carotid Endarterectomy
High Grade Stenosis
Carotid Endarterectomy
Carotid Stenting
For patients who are unable to undergo
surgery, the endovascular alternative to
surgery is carotid stenting. In this approach
a catheter that contains an expandable
region at one end is fed through the femoral
artery up into the carotid artery. The end of
the catheter is then expanded. This "balloon"
squeezes the plaque against the arterial wall,
increasing the effective diameter of the
artery.
Carotid Stenting
Carotid Stenting
A stent is then placed inside the artery. A
stent is a tubular arrangement of fibers
somewhat similar visually to wire fencing
rolled up into a tube. The stent reinforces the
carotid artery to prevent its collapse and to
keep the plaque tightly against the arterial
wall.
Carotid Stenting
Prevention
Prevention includes controlling the risk
factors. Hypertension, diabetes, heart
disease, and other associated disorders
should be treated as appropriate. Smoking
should be stopped. The use of blood
thinners may prevent strokes in some
patients who have blood clots or atrial
fibrillation.
Prevention
Aspirin is the most commonly used
medication, only a child's aspirin a day
before bedtime yields positive results.
Prevention options include life-style (risk
factor) modification (more exercise, better
diet). A reduced amount of sodium in the
diet to help control high blood pressure, a
diet for diabetics, reduced dietary fat, or
other dietary changes are also
recommended.
Prognosis
“With prompt medical treatment, including
surgery, recovery from carotid stenosis can
be complete with no residual effects. If
carotid stenosis is dealt with promptly by
surgery, medicine, or lifestyle modifications,
prognosis is good. For example, at the John
Hopkins Medical school, carotid stenosis
corrective surgery has a mortality rate of
0.8% and a morbidity rate of 1.8%”.
Conclusion
Strokes caused by embolization from atherosclerotic
disease at the carotid artery are common and can
occur without warning. Strokes are the third leading
cause of death in the Unites States; half of those
strokes are attributed to coronary stenosis. Most of
the risk factors that contribute to arterial disease are
within our own control. Diet, exercise and
preventative medications can help those who do
develop symptoms. Diagnosis is not a death
sentence with several very successful treatment
options such as Carotid Endarterectomy and Carotid
Stenting available.
The End