Pulmonary Arteriovenous Fistula
What is a Pulmonary Arteriovenous Fistula?
A pulmonary arteriovenous fistula is an abnormal blood vessel that creates a potentially
troublesome connection between a vein and an artery in the lung. It acts as a detour,
sidestepping the normal route the blood is supposed to take. If a patient has symptoms
or problems, medical attention is essential.
Pulmonary arteriovenous fistulas are congenital malformations—that is, they’re
present at birth. They appear slightly more often in females than in males. People
with hereditary hemorrhagic telangiectasis (HHT) sometimes have these fistulas in
different parts of the body, including the lungs. Pulmonary arteriovenous fistulas
more commonly appear on their own, independent of an underlying disease.
The Mechanics of Pulmonary Arteriovenous Fistulas
Pulmonary arteriovenous fistulas develop as the child develops in the womb. These
abnormal vessels carry blood out of the lung before it is oxygenated—that is,
replenished with oxygen. The process is called a “right-to-left shunting” of blood.
The outlook is less favorable for patients with HHT than for patients not suffering
In many cases there are no symptoms. In more serious cases, this circumstance
can starve the body of oxygen and lead to a variety of complications. In addition,
left untreated, these fistulas might lead to a “paradoxical embolism”—a blood clot
that travels from the lungs to the arms, legs or brain.
Symptoms of Pulmonary Arteriovenous Fistulas
The most common symptoms are difficulty breathing and blood in the patient’s sputum.
But symptoms also can include:
- Fingers and toes turning bluish
- Fingers and toes becoming puffy or enlarged (clubbing)
- A “murmur” in the lung· Nosebleeds in HHT patients
Causes of Pulmonary Arteriovenous Fistulas
Pulmonary arteriovenous fistulas occur in about one third of all patients with
HHT. But the majority of cases are present at birth. Doctors do not know what causes
them, and there is no known way to prevent them.
Diagnosing Pulmonary Arteriovenous Fistulas
A diagnosis usually begins with the patient “presenting” one or more of the symptoms.
The doctor will run tests to see if the oxygen level in the blood is abnormally
low, or if the red cell count in the blood is abnormally high.
In addition the common symptoms, if there is evidence of these blood conditions,
the following tests probably will be performed:
- Listening for a murmur in the lungs with a stethoscope
- A chest x-ray to locate the fistula
- A CT (computed tomography) scan to gather details about the fistula’s
structure and condition
- A pulmonary arteriogram—a video of dye moving through the blood vessels to map
Treating Pulmonary Arteriovenous Fistulas
Small pulmonary arteriovenous fistulas might require no treatment at all. In
most cases, however, these fistulas need to be corrected. There are two treatments
- Surgery to remove the abnormal blood vessel and nearby lung tissue
- Embolization (at the time of the arteriogram) to block the fistula and the
flow of blood
Surgery is almost always successful. With embolization, however, the problem can
recur if the blockage gives way or is overcome. For that reason, patients usually
are screened for “favorable anatomy” before a decision is made to perform an embolization.
Oxygen is Job 1
Of all the illnesses that can affect the lungs, a pulmonary arteriovenous fistula
might reveal their key function best. The lungs act as “transfer stations,” delivering
much-needed oxygen to the blood as it passes through them. Interrupt or sidestep
these deliveries and things break down. The good news: These deliveries can be
restored relatively easily with removal or repair of the fistula.