Pulmonary arteriovenous malformation

A pulmonary arteriovenous malformation is a rare, unusual connection between an artery and a vein in the lungs. It also is called a pulmonary AVM or PAVM. One estimate suggests that about 1 person in 2,630 has a PAVM.

Some people with PAVMs have no symptoms. But a PAVM can cause serious health complications, including stroke, bleeding and an increased risk of developing an infection in the brain called a brain abscess.

A PAVM can be treated with a procedure called embolization. This procedure blocks blood flow through the PAVM. It can be an effective treatment for PAVMs.

Types

An artery that carries blood into a PAVM is called a feeding artery. A vein that carries blood away from it is called a draining vein.

There are different types of pulmonary arteriovenous malformations (PAVMs). PAVMs are grouped as simple, complex or diffuse based on the structure of the blood vessels.

• Simple PAVM. This type has one artery that carries blood into the PAVM.
• Complex PAVM. This type has two or more feeding arteries that carry blood into the PAVM.
• Diffuse PAVMs. These PAVMs involve blood vessels in a larger area of the lung.
• Multiple PAVMs. These PAVMs involve multiple sites within the lung rather than multiple blood vessels.

You can have one or more PAVMs. Having more than one PAVM is different from having a complex PAVM.

The size and number of PAVMs and how much blood flows through them can affect whether you have symptoms. Having larger PAVMs or having several PAVMs can allow more blood to pass through the lungs without picking up enough oxygen. This may lower your blood oxygen level and make symptoms more noticeable.

Many people with pulmonary arteriovenous malformations (PAVMs) have no symptoms. When symptoms occur, some are related to lower oxygen levels because blood is bypassing the tiny blood vessels in the lungs where it typically picks up oxygen.

Symptoms may include:

• Trouble breathing.
• Tiredness or trouble with physical activity.
• Low oxygen levels in the blood.
• A change in skin or lip color caused by low oxygen levels.
• Chest pain.
• Coughing up blood.
• Clubbing.

Some PAVM symptoms may affect the whole body, not just the lungs.

To understand what causes a pulmonary arteriovenous malformation (PAVM), it can be helpful to know how the blood usually flows. Typically, blood flows through tiny blood vessels called capillaries into the lungs. There, the blood picks up oxygen before it goes back to the heart.

In a PAVM, some blood flows straight from a lung artery, called a pulmonary artery, to a lung vein, called a pulmonary vein. In a PAVM, some blood skips the capillaries and goes back to the heart without picking up enough oxygen in the lungs. This is called a right-to-left shunt. A right-to-left shunt can affect the whole body due to less oxygen in the blood.

Common causes of PAVMs include:

• Congenital occurrence. The unusual blood vessel connection may develop before birth or after surgery to correct some congenital heart conditions.
• Hereditary hemorrhagic telangiectasia (HHT). HHT is an inherited condition that affects blood vessels in different parts of the body. Not everyone with a PAVM has HHT.
• Cirrhosis. Long-standing liver disease may result in a PAVM.
• Injury to the chest. Trauma to the chest area may cause a PAVM.
• Fanconi syndrome. This uncommon kidney disease may result in a PAVM.

Pulmonary arteriovenous malformations (PAVMs) are more common in people with a condition called hereditary hemorrhagic telangiectasia (HHT), also known as Osler-Weber-Rendu syndrome. HHT is an inherited condition that affects the links between arteries and veins.

If you have HHT and have children, ask your child's healthcare team whether your child should be checked for HHT. HHT can affect children even if they do not have symptoms.

A pulmonary arteriovenous malformation (PAVM) can cause serious complications even when you have few or no breathing symptoms. In a PAVM, some blood bypasses the tiny blood vessels in the lungs that typically help your blood pick up oxygen and filter material from your bloodstream. As a result, your blood may carry less oxygen, and material that usually would be filtered out can travel to other parts of your body.

Complications may include:

• Stroke or transient ischemic attack (TIA). A blood clot can pass through a PAVM and travel to the brain. A TIA is a short-lasting interruption of blood flow to the brain. It causes strokelike symptoms that go away and do not cause long-term damage.
• Brain abscess. Bacteria can pass through a PAVM and lead to a serious infection in the brain called an abscess.
• Low blood oxygen. A PAVM can allow blood to return to the heart without picking up enough oxygen in the lungs. As a result, this can lower the oxygen level in the blood and may cause symptoms such as shortness of breath.
• Serious bleeding. A PAVM can bleed into the lung or chest and may cause coughing up of blood.

Some PAVM complications can be life-threatening.

You may need several tests so that your healthcare team can diagnose and evaluate a pulmonary arteriovenous malformation (PAVM).

Tests may include:

• Chest CT scan. This test uses X-ray techniques to create images of the lungs. It is an important test for finding and evaluating a PAVM. It can show the PAVM along with its feeding artery and draining vein. This helps your healthcare team tell a PAVM from a lung nodule or another structure that may look similar.
• Bubble study. This test also is called transthoracic contrast echocardiography. Tiny bubbles in a saline solution are injected into a vein while ultrasound pictures of the heart are taken. If the bubbles appear in the left side of the heart after a short delay, this can suggest that a shunt is present through the lungs. A bubble study can show that blood is bypassing the usual blood flow through the lungs.
• Chest X-ray. A chest X-ray is an imaging test that may show some PAVMs, but it can miss smaller ones.
• Pulmonary angiography. This test may be done when your healthcare team plans to perform a procedure called embolization to treat the PAVM. Pulmonary angiography uses a long, thin tube called a catheter and a substance called contrast that helps to show the PAVM's blood vessels. This test helps your healthcare team identify the feeding artery or arteries that need treatment.

On an imaging test, a PAVM can look like a small, rounded spot in the lung called a lung nodule. But a PAVM is not a lung nodule. A PAVM is an unusual connection between blood vessels.

Treatment for pulmonary arteriovenous malformation (PAVM) aims to block the unusual blood flow through a PAVM. It also aims to prevent serious complications such as stroke, brain abscess and coughing up blood. Embolization is the main treatment for PAVMs that need treatment.

In the past, a feeding artery measuring 3 millimeters (mm) wide was commonly used as a cutoff for deciding whether to treat a PAVM. The 3-mm cutoff is no longer considered an absolute rule. With advances in embolization techniques, some PAVMs with smaller feeding arteries can be treated.

Embolization

Embolization is a procedure that blocks blood flow through the PAVM.

During embolization, a healthcare professional places a thin tube called a catheter into a vein and guides it through the blood vessel to the PAVM.

An imaging test called pulmonary angiography helps show the feeding artery and draining vein so your care team can plan where to block the blood flow.

Your care team places small devices such as coils or plugs through the catheter to block blood from flowing through the PAVM. Blocking the feeding artery lessens or stops the right-to-left shunt.

After embolization, you may need to rest in bed for a few hours. PAVM embolization often can be done in a procedure room in an outpatient setting. Many people can go home the same day. Some people have chest pain after the procedure.

Serious complications from embolization are not common, but they can occur. A treated PAVM also can stay partly open or regain blood flow later. This is one reason that follow-up is important.

Surgery

Surgery is a procedure that involves removing the PAVM or the part of your lung that contains it. Your healthcare team may consider surgery depending on your condition and which treatment benefits you. Care teams use surgery much less often than embolization to treat PAVMs.

Follow-up after treatment

Follow-up imaging helps your healthcare team check whether a treated PAVM stays closed. It also can help your care team identify a PAVM that still has blood flowing through it or that has regained blood flow. You may need long-term follow-up if some treated PAVMs stay open or regain blood flow.

Prognosis

Pulmonary arteriovenous malformations (PAVMs) are often effectively treated with embolization. Serious complications from the procedure are not common.

However, some treated PAVMs can stay open or regain blood flow over time. You may need long-term follow-up for your care team to check treated PAVMs and look for PAVMs that need more treatment.

Untreated PAVMs can lead to serious complications such as stroke, brain abscess, low oxygen levels and bleeding.

If a healthcare professional thinks you might have pulmonary arteriovenous malformations (PAVMs), you may be referred to a doctor trained in lung disease, also called a pulmonologist.

Here's some information to help you get ready for your appointment.

What you can do

• Ask if there is anything you need to do before your appointment. For example, your healthcare professional may tell you not to eat or drink for a short time before certain tests.
• Write down your symptoms, including any that may not seem related to PAVMs.
• Write down important personal information. This includes any major stresses or recent life changes.
• Make a list of all the medicines, vitamins and supplements you take. Include those you buy without a prescription. Also include the doses.
• Consider inviting someone you trust to go with you. Someone who goes with you can help you remember information you are given and what you discuss.
• Write down questions to ask the healthcare team.

Writing down questions can help you make the most of your visit. For a PAVM, some basic questions to ask your care team include:

• What's the most likely cause of my symptoms?
• What tests do I need? How do I get ready for them?
• I feel OK. Do I still need treatment?
• Which treatments may help me?
• Are there other treatment options?
• I have other health conditions. How can I best manage them together?
• Do I need to change my activities, exercise or diet?
• Should I see a specialist?
• Is there any information that I can take home with me?
• What websites do you recommend?

Don't hesitate to ask other questions.

What to expect from your doctor

Your healthcare team is likely to ask you many questions. Being ready to answer them may save time to go over any questions or concerns you want to spend more time on. Your care team may ask:

• When did you first have symptoms?
• Do you always have symptoms, or do they come and go?
• How much do your symptoms affect your daily activities?
• What, if anything, makes your symptoms better?
• What, if anything, makes your symptoms worse?