An arteriovenous malformation (AVM) is an abnormal connection between an artery
(a blood vessel carrying blood
from the heart out to the body) and a vein (a vessel returning blood to the heart).
It's a shortcut that lets blood flow from an artery to a vein without passing through
tiny vessels called capillaries. That's important because oxygen and other nutrients
can only pass from the blood into the body parts that need them in capillaries.
Blood that takes a shortcut through an AVM returns oxygen-rich blood to the
heart instead of delivering it to the body where it's needed. That means some
of the heart's work is wasted, so the heart has to work harder than usual. Large AVMs
or multiple AVMs can waste so much of the heart's work that it cannot keep up.
What Are the Signs & Symptoms of an Arteriovenous Malformation (AVM)?
Bleeding from an AVM can be hard to stop. Frequent bleeding may lead to anemia.
Even small amounts of bleeding from an AVM inside the skull can be very dangerous.
AVMs may grow larger and cause trouble by pressing on other parts of the body.
What Causes Arteriovenous Malformations (AVMs)?
Arteriovenous malformations and venous
malformations are types of vascular malformations (also
called vascular anomalies). These are problems that happen when blood vessels (capillaries,
arteries, veins, or lymphatic vessels) don't develop as they should.
Doctors don't know what causes AVMs. Kids who have them are born with them, and
an AVM might get larger as the child grows.
AVMs can happen with some genetic syndromes, including:
Cobb syndrome: wine-colored birthmarks with AVMs in the spinal
hereditary hemorrhagic telangiectasia (HHT): AVMs in the lungs,
brain, and digestive tract
Parkes Weber syndrome: multiple AVMs in one arm or leg; the affected
arm or leg typically grows longer and larger than the same limb on the other side
Wyburn-Mason syndrome (also known as Bonnet-Dechaume-Blanc
syndrome): AVMs of the retina (the light-sensitive area in the back of the eye) and
brain, sometimes involving part of the face
How Is an Arteriovenous Malformation (AVM) Diagnosed?
An AVM is often found during an exam because a pulse may be felt in its vessels.
Then, other tools may be used to learn more about it and plan treatment, such as:
an ultrasound, to determine how much blood is flowing through
a CT scan or MRI, to see the AVM's size and how close it is to
normal body parts
an angiogram, to map of the AVM's blood vessels, which will help
doctors plan how to block blood flow to it
an MRA, or MRA angiogram, which combines the MRI and angiogram
techniques to map the AVM without using X-rays. Similarly, a CT angiogram can be performed.
a standard angiogram, which shows the arteries by putting dye
into a long thin tube (catheter) in the vessel while taking an X-ray
How Is an Arteriovenous Malformation (AVM) Treated?
The right treatment for an AVM depends on its location, size, and how it affects
Why treat an AVM?
When a child's heart must work harder than usual because of an AVM, prompt treatment
is important to prevent permanent changes. An AVM also might be treated to improve
pain, bleeding, or its appearance.
AVMs in the arms, legs, and body are easier to treat than AVMs in the head.
AVMs outside of the skull are treated with:
using catheter-guided tools to permanently block the arteries leading to the AVM
injection of a chemical into an AVM that shrinks the blood vessels
AVMs in the head are called intracranial AVMs and may be treated
with embolization, surgery using radiation
(radiosurgery), or surgery.
Embolization and sclerotherapy usually are done by interventional radiologists
(doctors who specialize in minimally
invasive, targeted treatments).
Treatment for an AVM depends on its location, size and the symptoms it causes.
A small AVM that's not in the head may never need treatment, but it could change as
a child grows. Some AVMs get bigger, so it's important to track its size and its effects
on a child's health and activities.