What is Catheter Embolization?

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 communication 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.

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What are some common uses of the procedure?

Catheter embolization may be used as the sole treatment or may be combined with other treatments such as surgery or radiation. In some cases it is an emergency means of controlling bleeding until the patient can undergo final treatment, if need be.

• 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.

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How should I prepare for the procedure?

At least one day before embolization you will receive instructions from 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.

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What does the equipment look like?

The x-ray equipment and catheters are the same as those used for catheter angiography. A wide variety of materials are 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.

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How does the procedure work?

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 mechanically 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.

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How is the procedure performed?

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 an 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 couple of minutes to prevent bleeding from the site of catheter insertion. You can expect to stay in bed for six to eight hours afterwards.

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.
 

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What will I experience during the procedure?

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.
 

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Who interprets the results and how do I get them?

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.

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What are the benefits vs. risks?

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.
• About one 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.

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What are the limitations of Catheter Embolization?

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).

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