| Catheter Angiography
What is Catheter Angiography? Back to Top
Angiography is a
type of x-ray that is done to image blood vessels in various parts of
the body, including the heart, brain and kidneys, so as to determine
whether the vessels are diseased, narrowed, enlarged or blocked
altogether. After passing a catheter through an artery leading to the
body area of interest, a contrast material is injected to highlight the
vessels when x-rays are taken. Today, many catheter angiographic
studies have been replaced by less invasive methods, such as computed
tomography (CT) angiography and magnetic resonance (MR) angiography,
that do not require that a catheter be inserted. Catheter angiography
still is widely used in patients who may undergo surgery, angioplasty,
or stent placement.
What are some common uses of the procedure? Back to Top
Common
reasons to do catheter angiography are to detect narrowing or blockage
of a blood vessel, identify abnormally dilated blood vessels, and
determine the site of internal bleeding. The procedure is able to:
- Show atherosclerotic disease in the carotid artery of the
neck, which may limit blood flow to the brain and even cause a stroke.
- Demonstrate an intracranial aneurysm or other disorders of the blood vessels in the brain.
- Indicate disease in the renal artery or help prepare for a kidney transplant.
- Determine the state of the aorta and detect an aneurysm of this vessel.
- Demonstrate a source of bleeding, such as a stomach ulcer.
- Help prepare for surgery on diseased blood vessels in the legs of patients who have severe leg pain when walking.
- Show the extent and severity of atherosclerosis in the coronary arteries.
- Surgeons
sometimes use angiography to plan an operation, like coronary bypass
surgery, or to decide on the best surgical procedure.
- Using
catheter angiography as an aid to see inside blood vessels, surgeons
can repair diseased vessels from within using tiny instruments and
inserting a stent to keep the vessel open.
How should I prepare for the procedure? Back to Top
If you
are to have a sedative during the procedure, you may be asked not to
eat or drink anything (except sips of water to take pills) for four to
eight hours ahead of time. Some hospitals, however, allow clear fluids
until shortly before the examination. Be sure that you have clear
instructions from your health care facility. You will probably receive
an intravenous (IV) sedative in preparation for angiography, and you
should not drive for 24 hours afterward. Because an observation period
is necessary before you can leave, you may be admitted to the hospital
for an overnight stay if you live more than an hour away.
If
you will be going home the same day, you should arrange alternative
transportation. After removing jewelry and donning a hospital gown, you
should empty your bladder. A small amount of blood will be drawn before
starting the procedure to make sure that your kidneys are working and
that your blood will clot normally, and an IV line will be set up.
Before
the procedure you will have to give your consent. This usually involves
a face-to-face talk with a physician, but in some cases you will read a
brief description of angiography or view a videotape instead. If you
have any allergies, you should tell the physician before the exam
begins. Also, the radiology staff should know if there is a possibility
that you may be pregnant.
What does the angiography equipment look like? Back to Top
The
angiographic catheter is a long plastic tube about as thick as a strand
of spaghetti. The x-ray equipment is mounted on a C-shaped gantry with
the x-ray tube itself beneath the table on which the patient lies. Over
the patient is an image intensifier that receives the x-ray signals
after they pass through the patient, amplifies them and sends them to a
TV monitor.
How does the procedure work? Back to Top
The
basic idea of catheter angiography is the same as a regular x-ray. The
x-rays passed through the patient's body are absorbed to different
degrees by various tissues, and each type of tissue has its own
distinctive appearance. A stream of dye, or contrast material, is
injected into the catheter to obtain a detailed picture from inside the
blood vessel. X-ray images are stored in a computer or captured on
film. In this way, the procedure can be viewed like a movie and played
over as often as necessary.
How is the procedure performed? Back to Top
A
small dose of sedative is usually given through the IV line, not to
make the patient sleep but to lessen their anxiety during the
procedure. Local anesthesia is injected into the skin at the site of
puncture, which is most often at the top of the leg at the site of the
femoral artery. A small incision is made after cleaning and shaving the
skin at this site in order to introduce the catheter into the artery.
The radiologist threads the catheter through the arterial system to the
desired location and then injects the contrast material. Usually
several sets of x-rays are taken and, after the procedure is completed,
the catheter is removed and the puncture site closed by compressing it
for about 10 minutes (or by using a special closure device). You will
have to lie flat for two to six hours after angiography, depending on
the reason for the exam, the catheter size, and the type of device used
to close up the artery. During this time, you should inform the nurse
if you notice any bleeding, swelling or pain at the site where the
catheter entered the skin. The entire procedure may take less than an
hour or as long as several hours.
What will I experience during the procedure? Back to Top
Injecting
a local anesthetic may sting briefly but makes the rest of the
procedure pain-free. You will not feel the catheter in your artery, but
when contrast material is injected you may have a feeling of warmth or,
occasionally, a slight burning sensation. The most difficult part of
the procedure may be lying flat for several hours.
Who interprets the results and how do I get them? Back to Top
The
radiologist will examine all of the images. In some instances, he or
she will discuss the findings with you. Otherwise, he or she will
report the findings to your physician, who in turn will discuss them
with you.
What are the benefits vs. risks? Back to Top
Benefits
- Catheter angiography presents a very detailed, clear and
accurate picture of the blood vessels. This is especially helpful when
a surgical procedure or some percutaneous intervention is being
considered.
- By selecting the arteries through which
the catheter passes, it is possible to assess vessels in several
specific body sites. In fact, a smaller catheter may be passed through
the larger one into a branch artery supplying a small area of tissue or
a tumor; this is called "superselective angiography."
- Unlike
computed tomography (CT) or magnetic resonance (MR) angiography, use of
a catheter makes it possible to combine diagnosis and treatment in a
single procedure. An example is finding an area of severe arterial
narrowing, followed by angioplasty and placement of a stent.
- The degree of detail displayed by catheter angiography may not be available with any other noninvasive procedure.
Risks
- You may have an allergic reaction to the dye, and this
could lead to a skin reaction, a drop in blood pressure, difficulty
breathing or even loss of consciousness.
- There is a
small risk that blood will form a clot around the tip of the catheter,
blocking the artery and making it necessary to operate to reopen the
vessel.
- If you have diabetes or kidney disease, the kidneys may be injured when contrast material is eliminated through the urine.
- Rarely,
the catheter punctures the artery, causing internal bleeding. It also
is possible that the catheter tip will separate material from the inner
lining of the artery, causing a block "downstream."
- Women should always inform their doctor or x-ray technologist if there is any possibility that they are pregnant.
What are the limitations of Catheter Angiography? Back to Top
Patients
with impaired kidney function, especially those who also have diabetes,
are not good candidates for this procedure. Patients who have
previously had allergic reactions to x-ray contrast materials are at
risk of having a reaction to contrast materials that contain iodine. If
angiography is essential, a variety of methods is used to decrease risk
of allergy. You may be given one or more doses of a steroid medication
ahead of time. Contrast material without iodine may be used instead of
standard x-ray dye. Catheter angiography should be done very
cautiously—if at all—in patients who have a tendency to bleed. Back to Top
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