Arteriovenous Malformations (AVMs)
An arteriovenous malformation (AVM) is a tangle of abnormally connecting arteries and veins. An arteriovenous fistula (AVF) is also a combination of vessels with abnormal connections. These two entities are very similar differing only in the type of connection between the artery and the vein.
As normal vessels course towards the region of brain that they supply, they divide into smaller and smaller branches. By the time they reach their destination, they have branched into many tiny vessels called capillaries. AVMs have abnormal connections between arteries and veins, with no capillaries between. The blood coursing through the abnormal vessels of an AVM is under high pressure. Veins are not used to such high pressure–they usually have the capillaries between them and the arteries to buffer that high pressure. Therefore there is the risk of rupture at this high pressure interface or the abnormality may exert pressure against the adjacent brain, resulting in seizures. A stroke can occur if blood that is supposed to supply a portion of the brain instead gets diverted through the AVM.
AVM’s can be treated from outside the blood vessels using surgery or radiation therapy. Alternatively the AVM may be treated from inside the blood vessels using endovascular embolization. Sometimes doctors use a combination of these three techniques.
A surgical approach requires brain surgery through an opening in the skull through which the surgeon’s instruments can enter. The AVM is removed, and any vessels supplying it are disconnected.The radiation therapy mode is called "radiosurgery" which is confusing since no surgery is actually performed. Radiosurgery tightly focuses a beam of radiation on the abnormal vessels and after a period varying between six months and two years the vessels gradually close off and are replaced with scar tissue. Radiosurgery is an option that is limited to AVM’s which are small.
Endovascular techniques can also be used to treat an AVM without brain surgery. The treatment is performed in the angiography suite with a catheter (a long thin tube) similar to that used during the arteriogram. Through the catheter, the AVM is blocked off (embolized) so that blood no longer flows through it. A variety of different materials may be used to close off the AVM, including types of biosafe glues and particles. Endovascular embolization of an AVM can be performed to cure the AVM by itself or before surgery to minimize blood loss, making the operation safer and shorter. It can also be performed before radiosurgery to make the AVM smaller and increase the chance that radiosurgery will be successful. The endovascular treatment of AVM’s is a relatively new procedure and requires specialized training. Most endovascular therapists are neuroradiologists who have completed additional training–ranging from one to three years–in endovascular techniques.
We should make sure you understand that multiple embolization procedures may be necessary to completely block off the AVM, or to block off as much as possible before surgery or radiosurgery. It is not unusual for you to have 2,3 or more trips to the neuroradiologist as he or she embolizes different areas of the abnormal connections between vessels. This is to ensure your safety. In general there are fewer abnormal connections with arteriovenous fistulas (AVFs) than arteriovenous malformations (AVMs).
How to Prepare:
You will be seen by a Neuroradiologist prior to your procedure, either in our clinic or on the day of the procedure. We will perform a thorough history and physical and review medications and any allergies you might have. Films such as CT scans and MRIs will be reviewed as well. A plan of treatment will be established and the details will be discussed with you. At that time, you will be given instructions for your procedure. We will need to have current labs. We will go over your medications and tell you which to take the morning of your procedure. You may be put on additional medications specific for the type of procedure you are having. If the Neuroradiologist orders the procedure to be done under General Anesthesia, you will be sent to the Pre Anesthesia Evaluation Center for part of the work-up. If your procedure can be done with nursing sedation, you will not need an anesthesia evaluation.
When your appointment is made, you will be given instructions as to where and when to come in for the procedure. You will also be given a phone number to call with questions. We ask that you follow medication instructions carefully. You will not be allowed to eat anything after midnight but you may drink clear liquids up until 2 hours before your procedure. Leave jewelry and other valuables at home. You must have someone to drive you home after your procedure. If your condition is treated during the angiogram, you will stay overnight in an ICU to be monitored, and go home the following day.
Where to go the day of the procedure:
You will need to check in at Radiology Reception one hour prior to your scheduled procedure time. This will give us time to get you ready. One of the staff will pick you up after you have registered.
What to bring:
Bring any existing CT, MRI, myelogram, and angiogram films and reports. If you have had a prior arteriogram bring those films or arrange to have them sent to us in advance of your test.
Bring information about existing conditions and medications.
Bring appropriate medical insurance materials.
What to Expect:
Prior to Your Procedure
When you arrive, you will be greeted by a member of our staff and registered for your procedure. A physician will explain your procedure, answer any questions, and have you sign a consent form. An intravenous line will be started in your arm to give you fluids and medications to relax you if you require them. You will be taken to the procedure room, where you will lie on your back during your angiogram. Cushions and pillows will be used to make you comfortable. The skin where the catheter will be inserted, which is usually in the upper thigh-groin region, will be cleansed, and you will be covered from the shoulders down with a sterile drape.
During your Procedure
The neuroradiologist will give you local anesthetic in your groin which may cause slight discomfort for a few seconds before going numb. A catheter will be inserted through a small incision in the skin. You will feel minimal pressure in the area. The catheter will be guided into the vessels to be examined.
When the neuroradiologist has placed the catheter in the correct position, contrast dye will be injected which may cause a warm, but not painful, feeling for a few seconds. During this time, you will also hear an x-ray machine taking pictures. It is important to remain still, without breathing or swallowing, while the dye is injected and the pictures are taken. A nurse will be with you at all times. Please tell us if you become uncomfortable.
You will probably not feel the effects of the occlusion of the AVM when it is embolized. We will be checking on you constantly to make sure you are feeling OK and are not having any neurologic problems during the procedures. You may be asked to perform simple tasks to ensure that the procedure is safely performed.
After your Procedure
In general, diagnostic procedures require about two hours of time to perform; therapeutic procedures typically require more. When your procedure is completed, pressure will be applied to the incision site for 10-20 minutes, after which a small bandage will be placed over the incision. No stitches are required. You will then need to lie on your back with your leg straight and still for four to six hours. A meal will be provided during this time.
After this procedure, you will be admitted to the hospital. This is so that we can monitor you and make sure that the procedure was successful and that you will have no problems thereafter.
If you are already an inpatient, you will be returned to your room for observation by your floor nurse.
The neuroradiologist will communicate the results of your examination to your physician, who will discuss the results with you at an appropriate time. The referring physicians often prefer that we refrain from discussing the findings with the patients, particularly before they have been notified.
After you Leave
You may resume your usual diet after the procedure. Fluid intake of 48-64 ounces during the next 24 hours is recommended as this aids in x-ray dye elimination.
Do not exert yourself for 24 hours following the procedure, after which normal activity may be resumed. If you are an outpatient, a family member or friend should drive you home and stay with you during the 24-hour period.
It is not unusual to have minor bruising around the incision, but if you experience bleeding or swelling there, or develop a cold or painful leg, contact us immediately.
We try to call our patients (outpatients) or visit them (inpatients) the day after the procedure. Please contact us at any time if you have concerns.
We are trained in the use of x-rays and every effort is taken to use the minimum of radiation. The small amount of x-rays used during routine neuroangiography will not be harmful to you. If you notice that the staff wear leaded aprons, it is because they work with x-rays everyday and their occupational exposure is high.
For additional information on the web, we recommend you click on the link below to visit the ACR and RSNA patient information site:
Billing and Insurance
If you are a self-pay patient, a bill will be issued at time of service and mailed to your home.
If you are covered by a commercial health insurance carrier, please bring your cards or proof of coverage should be brought with you the day of your study. We will file your claim for you. Please note that you will be billed for any balance not covered by your plan. If you belong to a Health Maintenance Organization (HMO) or Preferred Provider Organization (PPO) with which we have a contract, you must bring the referral and authorization form for the procedure to be covered.
If your visit is due to an accident (work-related, automobile, etc.), you must provide us with an authorization from the guarantor of your bill.
Note that separate bills are issued by the UVA (to cover facilities, equipment, and support personnel) and the Health Science Foundation (to cover the services of the physician neuroradiologists). So expect to see two bills for your study.