Cerebrovascular & Carotid
Artery Disease
How Can Carotid Artery Disease Be Diagnosed?
Introduction
Duplex Ultrasound
CT Scan
Magnetic Resonance Angiography
Angiography
Introduction
First your physician asks you questions about your general health, medical
history, and symptoms. In addition, your physician conducts
a physical exam. Together these are known as a patient history and exam.
As part of your history and exam, your physician will ask you if you smoke
or have high blood pressure. Your physician will also want to know when
your symptoms occur and how often.
During your exam, your physician will listen for sounds of
turbulent blood flow in your carotid arteries. He or she
may also measure your blood pressure.
After the history and exam, if your physician suspects you
have carotid artery disease, he or she will perform a carotid
duplex ulrasound. In this painless test, a technician holds
a small ultrasound probe to your neck. The probe emits high-frequency
sound waves that bounce off of blood cells and blood vessels
to show blood flow and problems with the structure of blood vessels. This
test can show your physician how open your carotid arteries are and how
quickly blood flows through them.
Carotid duplex ultrasound detects most cases of carotid artery
disease. Therefore, your physician usually may not need
to perform other tests. However, if ultrasound does not
provide enough information, your physician may order one or
more of the following:
- CT scan and CT Angiography (CTA): CT and CTA scans take
x-ray pictures in the form of slices of the brain and
the arteries in your neck. CT scans can show an area of the
brain that has poor blood flow. Your physician may inject
a contrast dye to make blood vessels visible on the x-ray
image. CTA shows the arteries in the next and head and will
identify areas of arterial narrowing.
- Magnetic resonance angiography
(MRA): MRA uses radio waves and magnetic fields to create
detailed images. Some forms of this test can show moving
blood flow and may help evaluate carotid artery disease.
To improve the test's accuracy, physicians sometimes inject
a material, called gadolinium, to make the arteries more visible.
- Angiography:
In this test, your physician injects a contrast dye through
a catheter that is threaded into your arteries and then takes x-ray pictures.
The structure of your arteries appears on the x-ray images because x-rays
themselves cannot pass through the dye. This test shows how
blood flows through the arteries and whether they are narrowed. Angiography
carries some risks, including a small incidence of stroke, which is one
reason that physicians do not always use it as the first test to diagnose
or follow carotid artery disease. Vascular surgeons also use angiography
during carotid angioplasty and stenting, which is discussed
later in this article
Duplex Ultrasound
What is duplex ultrasound?
Duplex ultrasound combines Doppler and conventional
ultrasound to allow physicians to see the
structure of your blood vessels. Duplex ultrasound shows
how blood is flowing through your vessels and measures the
speed of the flow of blood.
Conventional ultrasound uses sound waves higher
than the human ear can detect that bounce
off of blood vessels. A computer converts the sound waves
into two-dimensional, black and white moving images.
Doppler ultrasound measures how sound waves
reflect off of moving objects. A wand
bounces short bursts of sound waves off of red
blood cells and sends the information to a computer. Doppler
ultrasound produces two-dimensional color images that show
if blood flow is affected by problems in the blood vessels.
When performing duplex ultrasound, your
physician uses the two forms of ultrasound
together. The conventional ultrasound shows the structure
of your blood vessels and Doppler ultrasound
shows the movement of your red blood cells through the
vessels. Duplex ultrasound produces images that can be color coded to show
physicians where your blood flow is severely blocked.
You may have the test performed in an ultrasound lab. The lab may
be part of the physician's office or it may
be in a hospital. In some cases your vascular physician may perform the
test. Usually, however, a specially trained vascular ultrasound technologist
performs duplex ultrasound.
The test usually lasts about 30 minutes.
How do I prepare?
For most types of duplex ultrasound not involving
the abdomen, you will not have to follow
any special instructions. Your physician or the center
performing the test may have specific instructions for
a particular type of duplex ultrasound. For instance, you
may have to fast overnight before having an abdominal ultrasound.
Ultrasound waves cannot break through gas in the bowels or air in the lungs.
What happens during a duplex ultrasound?
Before the test begins, your physician or
the technician will ask you to lie
on the table with your head slightly elevated. The technician
will also ask you to lie still because any movement could
change the image. The technician then spreads a special gel
over the area that he or she will examine. The technician presses
the ultrasound wand against your skin and moves it back
and forth. As the wand moves back and forth, it sends the
information to the computer that produces the images. During
the test, you may hear a whooshing sound, which is the sound that the ultrasound
machine makes to represent your blood moving through your body.
What can I expect after a duplex ultrasound?
There are no special instructions for you
to follow after the test. You may
resume all of your normal activities.
Are there any complications?
Complications are very rare with
ultrasound.
CT Scan
What is a CT scan?
Computerized tomography scanning, also called
CT or CAT scanning, is a test that uses
x rays and computers to create detailed images
of the internal structures of the body. These images, known as CT scans,
show cross-sections, or slices, of your body.
CT scanning is painless and usually takes fewer than 30 minutes.
CT scans can show the anatomy of a variety
of sections of the body, including:
- Your abdomen, which contains important
blood vessels like your abdominal aorta
(your main artery) and your liver and kidneys
- Your
chest
- Your neck
- Your arms or legs
- Your brain
Your physician might order a CT scan to
help diagnose vascular conditions,
tumors, infections, and other conditions.
During a CT scan, you lie down on a
table. The table passes through
a donut-shaped device. Inside the device, a machine
takes x rays in arcs around the area
of your body being examined. Tissues of varying densities
absorb these x rays. The computer assigns these densities
different numerical values and then plots an image based
on these values, mainly in shades of gray. In general, CT scans
display bones as white, gases and liquids as black, and tissues
as varying shades of gray.
Physicians may find it helpful to
compare two CT scans of the same
anatomical area. One without the administration of a dye-like
material called contrast, and one
with this contrast material. Contrast material makes hollow
or fluid-filled structures more visible and highlights
the presence and extent of abnormalities, such as blood
vessel abnormalities, cysts, tumors, and abscesses.
How do I prepare?
If your test will include contrast, your
physician will ask you to avoid foods and liquids for about
4 hours before the test. If you will be having abdominal
contrast images, you will drink a liquid version of the
contrast agent 1 to 2 hours before your test.
Before the test is performed, you change into a hospital
gown and remove all jewelry and other metal
objects, which interfere with x rays. If you will be receiving
a head CT scan, you will be able to wear street clothes.
If you fear being in small, confined spaces, your physician
may give you a sedative to help you relax. If you
receive a sedative, you should arrange for a ride home after
the test.
Am I at risk for complications?
Because CT scanning is an x ray test, it sends radiation
through your body. The amount of radiation is small,
but radiation can damage body cells.
Contrast material carries a slight risk of causing
an allergic reaction. If you know that you are allergic
to contrast material or dye, let your physician know
before you receive the contrast material. The contrast
material is also eliminated by the kidneys and can affect
their function, especially if you have kidney problems
already.
You may be unsuited for a CT scan if you:
- Are pregnant, because radiation may harm the fetus
- Have an allergy
to contrast dye
- Have unstable vital signs
- Weigh more than 300 pounds, because the table
cannot support the weight
- Have kidney problems
What happens during a CT scan?
If the physician chooses to perform CT scanning
with contrast, he or she will inject the contrast material
into a vein in your arm or hand. The contrast material may
make your feel flushed, warm, and mildly sick to your stomach.
This will only last for about 30 seconds.
You will lie still on the scan table that slides
into the gantry, the donut-shaped device that houses the
scanning equipment. The machine is quiet and relatively
open; only the part of the body being examined lies inside
the gantry. As a medical technician operates the scanning machine in another
room, he or she watches and speaks to you through speakers in the
CT scan room.
An x ray tube slides around the gantry, passing
narrow beams of low-dosage x rays in an arc over the
body. These beams reflect onto a detector positioned opposite
the x ray source. After the x ray source completes an arc,
the scanning table moves forward a small distance and the
x ray source transmits another arc of x rays. The detector
transmits the x ray energy to a computer, which transforms the information
about the reflected energy into an image. To create images from different
angles, the technician adjusts the position of the scanning table.
You must remain still as the CT scanning machine
operates. The technician may ask you to hold your breath
for 20 seconds at a time, because even the motion of breathing
can blur the images. If you are being scanned for brain images,
you may rest your head on a rubber cap within a water-filled
box or within a stationary head brace.
The entire procedure usually takes 10 to 15
minutes.
What can I expect after a CT scan?
There are no restrictions after a CT scan and
you can resume normal activities immediately.
If your physician gave you a contrast agent,
you should drink fluids following the test to speed excretion
of the agent and to guard against dehydration.
Are there any complications?
The most serious complication of CT scanning
is an allergic reaction to the contrast dye. Reactions
usually occur immediately and include flushing, itching,
or difficulty breathing or swallowing. Notify your
physician if you experience any of these symptoms. Sometimes contrast
dye leaks under your skin at the injection site. This
can cause redness, swelling, or pain.
Magnetic Resonance Angiography
What is Magnetic Resonance Angiography?
"Magnetic resonance angiography (MRA) uses magnetic fields and radio
waves to produce two-dimensional or three-dimensional images of the structures
inside your body, such as blood vessels. MRA is also sometimes referred
to as MRI (magnetic resonance imaging) scanning. MRA helps your physician
diagnose the following conditions:"
- Bulges in your aorta, called aneurysms
- Tears in your aorta,
called dissections
- Problems with your
heart that you may be born with, called congenital heart
disorders
- Narrowing of the arteries in and around your kidneys,
called renal artery stenosis
- Inflammation in your blood
vessels, called vasculitis
- Hardening of the arteries (called
atherosclerosis) involving the legs or arms
- Blockages in
the major arteries that supply blood to your brain, called
carotid artery disease
The MRA equipment consists of a table that slides in and
out of a donut-shaped machine. A computer attached to the machine processes
radio waves and magnetic fields to create two-dimensional
or three-dimensional images.
MRA not only helps your physician diagnose
your condition, it also helps him or her plan treatment.
MRA also may, in some circumstances, have advantages that other
tests do not. For instance, MRA does not require X-ray exposure to detect
narrowing of arteries, unlike computed tomography (CT) scans or angiograms.
How do I prepare?
Your physician may ask you not to eat 4 to
6 hours before the test, but usually no other preparation
is necessary.
You may not be eligible for an MRA if you:
- Weigh more than 300 pounds
- Have a pacemaker or other metallic devices
inside your body, such as joints, pins, clips, or valves
- Are on continuous life support devices, such as oxygen
- Are pregnant
- Are claustrophobic
- Are extremely anxious, confused, or agitated
If you are claustrophobic, your physician may recommend an open
MRA.
What happens during an MRA?
Your physician will direct you to a special
lab or room where a technician will perform
the test. The technician will instruct you to change
into a hospital gown and remove any jewelry or metallic objects.
The technician may give you a sedative to make sure that you lie still
during the procedure.
The technician will ask you to lie on the
MRA table. The table slides slowly through
a hollow, donut-shaped chamber that exposes you to
magnetic fields and pulses of radio waves. These magnetic fields
and radio waves are harmless and painless. The only discomfort that you
may feel will be from lying still on the hard table in an
enclosed area.
During the test, the technician may speak
to you through a speaker that is inside
the MRA room.
Sometimes the technician may inject a contrast
dye into your hand or forearm to improve
the quality of the images.
An MRA lasts between 30 to 90 minutes.
What can I expect after an MRA?
Your physician will instruct you to arrange
for a ride home if you receive a sedative.
Are there any complications?
Complications from an MRA, such as
a reaction to the contrast dye, are very
unusual.
Angiography
What is an angiogram?
An angiogram uses x rays to view your body’s
blood vessels. Physicians often use this
test to study narrow, blocked, enlarged, or malformed arteries in many parts
of your body, including your brain, heart, abdomen, and legs. When the arteries
are studied, the test is also called an arteriogram. If the veins are studied,
it is called a venogram.
To create the x ray images, your physician
will inject a dye through a thin, flexible
tube, called a catheter. He or she threads the catheter
into the desired artery from an access point. The access point is usually
in your groin but it can also be in your arm. This dye, called contrast, makes
blood vessels visible on an x ray. Your physician will recommend an angiogram
to diagnose vascular conditions, including:
- Blockages of the arteries outside of your
heart, called peripheral artery disease (PAD)
- Enlargements
of the arteries, called aneurysms
- Kidney artery conditions, called renovascular
conditions
- Problems in the arteries that branch off the aorta, called aortic
arch conditions
- Malformed arteries, called
vascular malformations
Sometimes physicians can also treat a problem during an angiogram.
For instance, your physician may dissolve a
clot that he or she discovers during the test. A physician may also perform
an angioplasty and stenting procedure to clear blocked arteries during an angiogram,
depending on the location and extent of the blockage. An angiogram can also
help your physician plan operations to repair the arteries for more extensive
problems.
How do I prepare?
Your physician will perform blood tests to
determine your blood’s ability to clot
and to assess your kidney function. Based on the test results, your physician
may instruct you to stop taking aspirin or other drugs that prevent clotting.
Your physician will also tell you which medications you should continue
to take. Usually your physician will ask you not to eat or drink anything
within 6 hours of your angiogram. Because you shouldn't drive after an
angiogram, you should arrange for a ride home.
Am I at risk for complications?
Blood clotting problems, kidney problems,
and advanced age can increase your
risk for developing complications during and after an angiogram. Allergies
can increase your risk of a reaction to the contrast dye.
What happens during an angiogram?
Your test will take place in a room equipped
with a specialized x ray machine. Your
physician will insert an IV to provide
you with fluids and medications. Your physician will choose where
to insert the catheter, usually into an artery in your groin
or your elbow. Before the insertion, he or she will clean your skin and shave
any hair to reduce your risk of infection. Your physician numbs
your skin with a local anesthetic and then makes a tiny puncture to reach
the artery below. He or she punctures your artery with a hollow
needle, advances a thin wire through the needle, threads a
catheter over the wire, and guides it to the desired location.
Your physician takes x rays that are projected on a video screen to see
the catheter as it moves through your arteries.
Once your physician has positioned the
catheter properly, he or she injects
the contrast dye. The contrast causes a brief,
mild warm feeling as it enters your bloodstream.
Your physician takes more x ray images
to see how the contrast is flowing through your arteries. During
the test, your physician may ask you to hold your breath for
about 5 to 15 seconds. In addition, your physician may ask
you to lie perfectly still to prevent sudden movements from blurring
the x ray pictures.
When the test is over, your physician will
remove the catheter and press the insertion
site for 10 to 20 minutes to help stop
bleeding.
Angiograms generally take about 1 hour
to complete if only xrays are required.
It may take longer if your physician also
performs angioplasty and stenting.
What can I expect after an angiogram?
After the test, the medical team will monitor
you for about 6 hours. During this time,
you should keep the arm or leg that was
punctured straight to minimize bleeding
from the puncture site. You will also
be asked to drink fluids to prevent dehydration
and flush the dye from your kidneys.
Once any bleeding from the insertion site has
stopped and your vital signs are normal,
your physician will tell you that you can
leave.
At home, you can eat normally, but you
should continue drinking extra fluids
for 1 to 2 days. For at least 12 hours
after the angiogram, avoid physical activities
such as climbing stairs, driving, and
walking. You should be able to resume normal
activities within a day or two of the procedure.
Are there any complications?
Complications from angiography include
bleeding, pain, or swelling where the
catheter was inserted, and pain, numbness, or coolness
in your arm or leg. Bruising at the
puncture site is common and usually resolves on
its own.
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