Peripheral Arteriovenous Malformations
When your blood vessels form incorrectly, disrupting communication between your arteries and your veins, you have an arteriovenous malformation (AVM). Typically, AVMs occur in the head, neck, and spine. If an AVM is anywhere else, including the arms, legs, heart, lungs, liver, or the reproductive or genital system, we call it a peripheral arteriovenous malformation.
Blood circulates in our bodies through blood vessels called arteries, capillaries, and veins. It leaves the heart in arteries, and then goes to the capillaries. Capillaries are the smallest blood vessels and pass through every tissue of the body carrying blood with oxygen and nutrients to the cells of the body. After the body takes what it needs from the blood, and deposits carbon dioxide and waste products into it, capillaries carry it back to the veins, which carry it back to the heart. The blood pressure in the normal veins is much lower than the blood pressure in the arteries.
If you have an arteriovenous malformation, some of the capillaries are replaced by larger channels that connect the arteries directly to the veins. The direct connection is called a shunt because it diverts the blood from the artery directly to the vein, bypassing the capillaries. We call these channels the “nidus” and they can consist of many tiny shunts or a smaller number of large ones.
In a peripheral AVM, the nidus reduces the blood supply with its nutrients and oxygen to the tissue around it, which raises the blood pressure in the draining veins and increases the amount of blood going through the arteries and veins. Over time, this process damages the surrounding tissue and forces your heart to work harder to circulate the blood.
The symptoms of peripheral AVM vary based on the size and number of shunts and the amount of tissue involved. In general, an AVM causes your tissue to enlarge because your arteries and veins expand and your affected tissue grows faster and larger than normal tissue. When there is an extremely large shunt, a peripheral AVM can cause heart failure.
Most AVMs get bigger over time. They often start out quietly and you may find that the skin over the AVM is reddish and warm. As the AVM progresses, your veins expand and the spot swells. If your peripheral AVM continues to progress, it can damage your tissue, causing pain, pressure sores and ulcers, and possibly bleeding.
It is hard to predict how quickly AVM will progress. It often takes years before it does real damage. Hormonal changes during puberty or pregnancy, trauma or injury, and surgery can affect how quickly the AVM grows.
Sometimes you can alleviate the swelling and discomfort from an AVM in your arm or leg by wearing a graded elastic compression sleeve or stocking. The compression stocking or sleeve squeezes the enlarged veins and reduces the swelling.
Another approach is embolization, which we typically do in a series of procedures spread out over time. It is important that we close the shunts themselves, not the feeding arteries or draining veins, using a permanent embolic agent such as embolization glue, Onyx liquid agent, and absolute ethanol.