Arteriovenous malformation embolization

Normally, blood flows from arteries into a web of tiny vessels called capillaries, which slow it down and feed the tissue, and then into veins. In an arteriovenous malformation (AVM), some arteries connect straight to veins, skipping the capillaries. The center of these abnormal connections is called the nidus, from the Latin word for nest. Blood rushes through at high pressure, and over time the veins stretch and the tissue around them can swell, hurt, break down or bleed.

AVMs are present from birth and can be found almost anywhere: the arms and legs, pelvis, face, lungs, kidneys or liver. This page covers AVMs outside the brain and spine, which are treated by interventional radiologists. Brain AVMs are usually treated by neurointerventional and neurosurgery teams. For the bigger picture, see arteriovenous malformations and vascular malformations.

Embolization means blocking blood vessels on purpose. For an AVM, the goal is to fill and seal the nidus and the start of the draining vein, so blood has to take the normal route again.

Treating an AVM that causes no symptoms is not always wise. Partial treatment can sometimes make an AVM more active. That is why we weigh the risks carefully and treat when the benefit is clear, with one important exception: lung AVMs are often treated even without symptoms, because they carry a risk of stroke.

Surgery can cure an AVM if the whole nidus is removed, but when the AVM involves muscle, organs, nerves or tendons, surgery can cause more harm than good. Embolization and surgery are often combined, with embolization done 1 to 3 days before surgery to make the operation safer. Compression garments help with swelling and pain but do not treat the AVM itself.

We start with an ultrasound, often in the office, and an MRI or CT scan to confirm the diagnosis and map the AVM. Complex cases are reviewed by a team that includes interventional radiology and vascular surgery. Sometimes we do a separate diagnostic angiogram first, to see exactly which arteries feed the AVM and how fast the flow is, and then bring you back for staged treatment.

1. 1
   Getting comfortable

   The procedure is done at El Camino Hospital in Mountain View, in a room with X-ray, ultrasound and CT imaging. You receive local numbing and twilight sedation, or general anesthesia for large, painful or complex AVMs.

2. 2
   Mapping the AVM

   A small tube is placed in the groin or wrist artery, or a thin needle is placed directly into the malformation. Contrast dye shows the feeding arteries, the nidus and the draining veins.

3. 3
   Closing the connections

   We deliver embolic agents into the nidus: liquid glues or gels that harden in place, alcohol that seals the vessel lining, or tiny coils and plugs. Sometimes a vein is temporarily blocked with a balloon to slow flow while we work.

4. 4
   Checking and finishing

   Repeat pictures confirm how much of the AVM is closed. The tubes are removed and pressure or a closure device seals the pinhole. No stitches are needed.

What we see

Before every AVM embolization I study the angiogram frame by frame to see exactly where the arteries meet the veins, because that meeting point is what has to be closed. Blocking only the arteries feeding it is like closing a highway exit: the traffic just finds another route. I tell patients up front that we usually work in stages, and that my first priority is to protect the normal skin, nerves and muscle around the AVM.

Fabio Komlos, MD, interventional radiologist · About Dr. Fabio Komlos

You are monitored for at least 2 hours to make sure there is no bleeding. Most people go home the same day. After a large treatment or general anesthesia, you may stay overnight.

1. First 24 hours
   Rest with the treated area raised. No driving, alcohol or important decisions after sedation. You may shower the next day unless told otherwise.
2. Days 2–5
   Pain and swelling are usually at their worst, and can be significant. Take prescribed pain medicine and anti-inflammatories, use ice, and keep the area raised. Sometimes steroids are given to calm the swelling.
3. 1–2 weeks
   Swelling goes down and most people are back to normal activity. The area may feel firm as the treated vessels scar down. Avoid heavy lifting with a treated arm or leg until comfortable.
4. About 1 month
   Clinic visit, and imaging if needed, to decide whether another session will help. Visits continue until symptoms settle.

Results depend a lot on the type of AVM. Small AVMs, especially those that drain into a single vein, have a good chance of being cured with embolization alone. Large, widespread AVMs are often not curable, and the goal is to control pain, bleeding and swelling. Most people have at least some improvement in their symptoms after treatment.

AVMs can come back, sometimes years later, as new vessels grow in. Repeat treatment is common and is part of the plan, not a failure. Hormone changes, injury and surgery can make an AVM more active, so long-term follow-up matters.

Because every AVM is different, we will talk through the specific risks in your case before treatment.