| Catheter Embolization
What is Catheter Embolization? Back to Top
Embolization is a
way of occluding (closing) one or more blood vessels that are doing
more harm than good. Various materials may be used, depending on
whether vessel occlusion is to be temporary or permanent, or whether
large or small vessels are being treated. The material is passed
through a catheter (a small plastic tube) with its tip lying in or near
the vessel to be closed. This approach can be used to control or
prevent abnormal bleeding as well as shut down the vessels that support
a growing tumor. Therapeutic embolization may also serve to eliminate
an arteriovenous malformation (AVM), an abnormal connection between an
artery and a vein. The term "embolization" derives from embolus, which
can be any object that circulates in the bloodstream until it lodges in
a blood vessel—in this case, a synthetic material or medication
specially designed to occlude the blood vessels.
What are some common uses of the procedure? Back to Top
Catheter embolization may be used as the sole treatment or may be combined with other treatments such as surgery or radiation.
The most common use of catheter embolization is to control bleeding
from injury, a tumor, a stomach ulcer or some other cause on an
emergency basis. Controlling bleeding into the abdomen or pelvis from
injuries caused in an auto accident is especially suitable for this
approach.
Occluding the blood vessels that feed a tumor can help control
symptoms when the tumor cannot be removed or might be difficult and
risky to remove, such as liver cancer. All tumors need a rich supply of
blood to continue growing. After embolization a tumor may shrink, or it
may continue to grow but more slowly than before. It now is possible to
combine the embolic material with chemotherapy, which may better treat
the tumor.
Fibroid tumors of the uterus, though not malignant (cancerous), may
cause long menstrual periods or heavy menstrual bleeding. They also may
produce pain in the pelvic area or the back, as well as pressure on the
bladder or bowel. Embolization may prove to be an alternative to the
surgical removal of the uterus (a hysterectomy). Because fibroids have
a large blood supply they will tend to shrink or even disappear if this
blood supply is interrupted. Multiple fibroids can be treated in the
same session. (See the Uterine Fibroid Embolization page for a detailed
description.)
Embolization is an excellent therapy for treating arteriovenous
malformations (AVMs). These lesions may occur anywhere in the body,
including the brain or spinal cord. AVMs are treated because the
abnormal connection of the artery and vein has the effect of a "short
circuit." The blood does not go where it is needed; instead it is
pumped through the connection (shunt) and back to the heart. AVMs are
commonly treated by embolization because of potentially severe
complications of surgical treatment. An AVM is a rare abnormality that
may cause pain and loss of function; embolization may control these
symptoms.
Embolization may also be used to plug the artery
supplying an aneurysm (ballooning out of the artery wall) within the
brain as an alternative to surgery.
Hemangiomas are highly vascular tumors often found on the face,
where they may deform and discolor the skin. Embolization is a sensible
alternative to surgical removal, which may leave an unsightly scar.
How should I prepare for the procedure? Back to Top
At least
one day before embolization you will receive instructions from the
office staff of the physician who will be performing the procedure—an
interventional radiologist. Prior to the procedure you may have blood
drawn at the hospital or at a local clinic to learn how well your
kidneys are functioning and whether your blood clots normally. Staff
also will advise you if there is to be a change in your medication
schedule. You will be admitted to the hospital the morning of the
embolization and examined by the radiologist before the procedure
begins. Do not eat or drink after midnight the morning before the
procedure, unless specifically instructed otherwise.
Prior to embolization, ultrasound, CAT scan or magnetic resonance imaging (MRI) will be performed as a necessary first step.
What does the equipment look like? Back to Top
The x-ray
equipment and catheters are the same as those used for catheter
angiography. A wide variety of materials is available to plug blood
vessels. Some are intended to occlude only very small arteries or large
ones, and some to occlude the vessels either temporarily or permanently.
Gelfoam™, a gelatin sponge material, is cut into small pieces that
are injected into an artery and float downstream until they can go no
farther. In this way the artery can be blocked for a few days or up to
two weeks. Gelfoam is used to control bleeding until the cause—such as
a bone fracture—can be identified and fixed, or until it has time to
heal on its own.
Permanent particulate agents, including Polyvinyl alcohol (PVA) and
gelatin-impregnated acrylic polymer spheres, are suspended in liquid
and injected into the bloodstream to block small vessels. These agents
are used to occlude vessels permanently. They are used to stop bleeding
or block arteries to a tumor when the underlying lesion is not likely
to heal. They are the materials used most often to embolize uterine
fibroid tumors.
Metal coils made of stainless steel or platinum may be used to
occlude large arteries. They can be positioned very precisely to stop
bleeding from an injured artery or halt arterial blood flow into an
aneurysm. The coils come in a range of sizes, allowing the radiologist
to choose one that will match the size of the artery.
Liquid sclerosing agents such as alcohols are used to purposely
destroy tissue. This might be desired to treat a large malformation of
veins by filling it with the liquid to induce clotting and damage the
inner lining of the veins. In successful cases the veins close up and
the malformation becomes much smaller.
Glue that starts out in a liquid state to penetrate small vessels
and then hardens is the most effective embolic material for treating an
arteriovenous malformation (AVM) in the brain.
How does the procedure work? Back to Top
Temporary embolic
agents block up blood vessels a long enough time (days to weeks) for
the body to heal the underlying health problem. For example, after a
car accident, Gelfoam embolization can stop internal bleeding. After
several days the body begins to heal the injury. By the time the
Gelfoam dissolves, the healing process at the site of injury is far
enough along to prevent rebleeding. Permanent embolic agents physically
plug-up blood vessels and cause scar tissue to form in the vessel that
doesn't go away. This is important in treating arteriovenous
malformation and tumors; in these cases, if the embolic agent
dissolved, the problem could recur. In all embolization procedures, the
radiologist will inject contrast material into the vessel to measure
the progress of the procedure and to decide when embolization is
complete.
Uterine fibroids and other types of tumors, like all tissues, depend
on a steady supply of oxygen and nutrients that are carried by the
arteries that feed them. Once the supply is cut off by embolization,
the tissue starts to break down and, in successful cases, the tumor
grows smaller or occasionally is eliminated.
How is the procedure performed? Back to Top
The first step
is angiography (injection of x-ray dye into an artery or vein) to
locate the exact site of bleeding or abnormality. A sedative is
injected through an intravenous line to relax you. Occasionally a
general anesthetic is given instead. The radiologist will numb an area
of the groin just over the hip joint with a local anesthetic. A thin
plastic tube (catheter) is introduced through a very small incision
into the femoral artery, a large groin blood vessel, and guided by TV
monitoring as close as possible to the area of abnormality. Contrast
material then is injected and a series of x-rays are taken where even
tiny thread-like vessels can be seen. An appropriate embolic material
then is chosen and injected through the catheter to lodge at the
treatment site. Repeat angiograms are done until bleeding is controlled
or there is enough embolic material in a tumor or vascular
malformation. At the end of the procedure the radiologist removes the
catheter and presses on the groin area for a short time to prevent
bleeding from the site of catheter insertion. You can expect to stay in
bed for six to eight hours afterward.
When uterine fibroids are treated, the arteries serving the uterus
are catheterized and embolic material is introduced (see the Uterine
Fibroid Embolization page). The procedure can cause pelvic pain, which
is controlled during the procedure with intravenous or epidural pain
medication. Fibroid embolization frequently requires overnight
hospitalization.
If you are treated by embolization for an intracranial arteriovenous
malformation (AVM), a small test injection of embolic material is done
first and neurological function is tested to make sure that no
important brain area will be damaged. Each vessel feeding the AVM then
is injected. Large AVMs may require multiple embolization procedures on
separate days for complete treatment. For example, two or three
treatments may be given at intervals of two to six weeks.
What will I experience during the procedure? Back to Top
The
intravenous (IV) sedative will make you feel relaxed and sleepy and you
may nod off for brief periods, but generally you will remain awake
throughout the procedure. You may feel slight pressure when the
catheter is inserted, but no serious discomfort. Most patients
experience some side effects after embolization. Pain is the most
common and can readily be controlled by oral or intravenous medication.
It occurs because the oxygen supply to the treated area is cut off.
Women who have embolization of fibroid tumors may have severe pain or
cramps, not during the procedure but for eight to 12 hours afterward.
Occasionally pain continues for as long as three or four days and may
require IV treatment in the hospital. Mild headache may follow
embolization of an intracranial arteriovenous malformation (AVM). Most
patients leave the hospital within 24 hours of the procedure, but those
who have considerable pain may have to stay for up to 48 hours. A
majority of patients can resume their normal activities within a week.
You may or may not remember some things about the procedure. Your
radiologist probably will want to check your condition six weeks after
embolization and again after three months and six months.
About one in five patients treated for fibroids will develop what is
called post-embolization syndrome, which consists of fever (up to 102°
F) that may be accompanied by loss of appetite and nausea or vomiting.
The syndrome may occur after any embolization procedure, but is more
prone to develop when a solid tumor is embolized. The symptoms usually
resolve within three days, though they sometimes last longer and
require medication to improve symptoms. These symptoms are the body's
reaction to breakdown products from the tumors and are most common when
very large tumors are embolized.
Who interprets the results and how do I get them? Back to Top
The
radiologist can advise you as to whether embolization was a technical
success when the procedure is completed. In cases of bleeding, it may
take 24 hours to know whether it has stopped. After embolization of a
tumor, uterine fibroids or arteriovenous malformation (AVM), one to
three months may have to pass before it is clear whether symptoms have
been controlled or eliminated.
What are the benefits vs. risks? Back to Top
Benefits
- Embolization is a highly effective way of controlling bleeding, especially in an emergency situation.
- Worldwide success rates of 85 percent and higher have been reported in women treated with embolization for uterine fibroids.
- Embolization
is much less invasive than conventional open surgery. As a result,
there are fewer complications and the hospital stay is relatively
brief—often only the night after the procedure. Blood loss is less than
with traditional surgical treatment, and there is no obvious surgical
incision.
- This method can be used to treat tumors
and vascular malformations that either cannot be removed surgically or
would involve great risk if surgery was attempted.
- When
embolization is used to treat an intracranial arteriovenous
malformation (AVM), injection of a small amount of material minimizes
the risk of serious brain dysfunction.
Risks
- There is always a chance that an embolus can lodge in the
wrong place and deprive normal tissue of its oxygen supply. If this
happens when treating an arteriovenous malformation (AVM) in the brain,
a stroke may result.
- There is a risk of infection after embolization, even if an antibiotic has been given.
- A
small percent of women have uterine injury from embolization of fibroid
tumors (see the Uterine Fibroid Embolization page), and this may make
it necessary to remove the uterus. In a few cases in women over age 45,
menopause has begun within one year of embolization of fibroids. The
effect of fibroid embolization on fertility is not clearly understood;
patients who wish future fertility should consult carefully with their
interventional radiologist prior to pursuing fibroid embolization as a
treatment option.
- Because angiography is part of the procedure, there is a risk of an allergic reaction to contrast material.
- Because
angiography is part of the procedure, there is a risk of kidney damage
in patients with diabetes or other pre-existing kidney disease.
What are the limitations of Catheter Embolization? Back to Top
Technically
successful embolization without injuring normal tissue requires that
the catheter be placed in a precise position. This means that the
catheter tip is situated so that embolic material can be deposited only
in vessels serving the abnormal area. In a small percentage of cases,
the procedure is not technically possible because the catheter cannot
be positioned appropriately. Whether clinical success is achieved
depends on many factors, including the size of a tumor, the location of
an arteriovenous malformation (AVM), and how the patient views the
outcome. Several sessions of embolization may be needed to reduce
symptoms from an AVM. Uterine fibroids respond well in a large majority
of cases, but perhaps 10 percent of women fail to improve (see the
Uterine Fibroid Embolization page). Back to Top
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