Arteriovenous Malformations (AVM)

People with HHT are missing capillaries in some of their blood vessels. These abnormal blood vessels are known as arteriovenous malformations (AVM). Because there’s nothing to lower the pressure of the blood before it flows into the veins, people with HHT often experience strained veins that may eventually rupture. When large AVMs occur, hemorrhages can occur. Hemorrhages in these areas can become life-threatening: the brain, the lungs, the liver, the gastrointestinal tract. AVMs can be particularly dangerous when they occur in the brain. When one bleeds, it can cause seizures and minor strokes.

Symptoms of a hemorrhage depend on location of the AVM, as well as the severity of the bleed. These symptoms may include: sudden and severe headache, nausea, vomiting, seizure, loss of consciousness, “stroke-like” symptoms, problems speaking, numbness, tingling, muscle weakness, changes in vision.

Though most people with it lead perfectly normal lives, HHT is life-threatening when an internal AVM begins to bleed uncontrollably. Visit your doctor regularly, so that they can monitor any internal AVMs.

AVM Quick Facts

  • AVMs arise in the brain, spine, lungs, kidneys and skin. Brain AVMs are the most common.
  • The overall ratio of AVMs to aneurysms is probably in the range of 1:10.
  • Most patients present between the ages of 20 and 60 years of age. The mean age is about 35-40.
  • AVMs are equally distributed between male/female.
  • Patients with AVMs may have additional vascular anomalies that increase the complexity of treatment. Approximately 10-58% of patients have various kinds of aneurysms.
  • It is estimated that in the United States 18 in 100,000 have an AVM in the brain.
  • When an AVM bleeds, there is a 10-15% risk of death related to each bleed and a 20-30% chance of permanent brain damage.
  • The risk of bleeding is higher in the first years after the first bleed.
  • In about 50% of patients the presentation is a sudden hemorrhage, or bleeding into the brain, a form of stroke. Other potential complications include seizures, headaches, and stroke-like symptoms (difficulty with movement, speech, and vision). These complications may occur in conjunction with, or independently of, hemorrhage.
  • About 5-10% of AVMs are discovered by accident while the individual is being tested for other unrelated medical problems.