Pulmonary Arteriovenous Malformation

A pulmonary arteriovenous malformation (PAVM) is an abnormal connection between blood vessels in your lungs. This connection disrupts normal blood flow between your heart and lungs. This can mean you’re more likely to have low blood-oxygen levels or get blood clots that could lead to a stroke.

Blood normally flows through your heart and into pulmonary arteries, which carry it to your lungs. From there, the blood enters tiny blood vessels (capillaries) that add oxygen, remove carbon dioxide and filter out particles, like blood clots. It then enters pulmonary veins and returns to your heart, where it gets pumped out to your body again.

PAVM lets some blood flow directly from a pulmonary artery to a pulmonary vein, without going through capillaries first. Your capillaries are an important stop. Without it, blood clots can escape filtering and go back out to your body. Plus, your body may not be able to exchange oxygen and carbon dioxide as it should. You can think of a PAVM like a shortcut that connects two roads but keeps you from passing by a gas station when you need one.

In general, PAVMs are rare. But they’re common among people who have a genetic condition called hereditary hemorrhagic telangiectasia (HHT). PAVMs are especially dangerous during pregnancy.

PAVM types

There are three main types of PAVM based on their structure:

• Simple: Just one artery leads into the PAVM. This is by far the most common type.
• Complex: Two or more arteries lead into the PAVM.
• Diffuse: Multiple arteries in one or more lung lobes connect to PAVMs.

Symptoms of pulmonary arteriovenous malformations

Many people with a PAVM don’t have any symptoms. But it’s possible to experience a range of symptoms affecting different parts of your body, including your cardiovascular and respiratory systems. You may have:

• Shortness of breath
• Limited ability to exercise
• Heart palpitations
• Chest pain or discomfort
• Cough (you may cough up blood)
• Bluish skin, lips and/or nails
• Clubbed fingers and toes

If you have HHT, you might also have nosebleeds. But this is a symptom of HHT, not PAVM.

PAVM causes

A difference in your genes causes pulmonary arteriovenous malformations. These changes are present at birth (congenital). Most people with a PAVM also have HHT. Certain gene changes in HHT affect how blood vessels form during fetal development. The most common genes affected are ENG, ACVRL1 and SMAD4.

These gene changes cause your pulmonary arteries and veins to connect in ways they shouldn’t — typically by forming a “sac.” That’s a bulging area that allows blood to flow directly between an artery and a vein. This keeps some blood from traveling to your lung capillaries. Instead, blood can reroute directly back to your heart — a bit like taking the wrong exit at a roundabout.

PAVMs rarely occur in people who don’t have HHT. This can also happen if you have trauma to your chest or complications from certain surgeries, like the Glenn procedure. Sometimes, the cause is unknown.

Complications of this condition

PAVMs can be dangerous because they allow unfiltered blood to move through your arteries. Normally, your lung capillaries filter blood to remove things that could harm you, like blood clots and small air bubbles. When some blood skips that step, clots and other debris could flow through your arteries and cause problems. PAVMs also keep some of your blood from picking up oxygen and getting rid of carbon dioxide.

Possible complications include:

• Migraines: Migraines affect about 2 to 4 out of every 10 people with a PAVM. Experts don’t know the exact reasons why.
• Stroke or transient ischemic attack (TIA): Blood clots can get stuck in an artery that supplies blood to your brain. This keeps your brain from getting enough blood, leading to a stroke or TIA.
• Brain abscess: Blood clots can sometimes get infected — for example, if bacteria get into your bloodstream during a dental procedure. The infected clot can travel to your brain, causing life-threatening issues.
• PAVM rupture: The PAVM “sac” has thin walls that can burst. This may lead to life-threatening internal bleeding and may present as coughing up a significant amount of blood. While this is a rare complication overall, the chances go up during pregnancy.

A healthcare provider will perform a physical exam and run tests. In some cases, providers suspect PAVMs because of an imaging test, like a chest X-ray or chest CT scan, that you had for other reasons. If this happens, they’ll run further tests to confirm the diagnosis. If you’ve been diagnosed with HHT, your provider will check for any signs of PAVMs, as they’re such a common feature.

Tests that commonly diagnose PAVMs include:

• Bubble study: A provider injects a substance with “microbubbles” into your veins while taking pictures of your heart and lungs. If the bubbles appear on the right side of your heart after a delay, that’s a sign of PAVM. It means some blood isn’t reaching your lung capillaries.
• CT scan: This imaging test can show PAVMs in great detail, including their exact location. Your provider may do this test if a bubble study comes back “positive” for the presence of a PAVM.

How are pulmonary arteriovenous malformations treated?

Treatment depends on the size and structure of the PAVM and how it’s affecting your body. You may not need treatment right away for a small, simple PAVM that doesn’t cause symptoms. Most PAVMs remain stable in size and can be monitored. Your provider will run imaging tests regularly to keep a close eye on your health. Complex or diffuse PAVMs, or any that cause symptoms, usually need treatment.

Treatments include:

• Embolization: This minimally invasive procedure is the most common treatment. Your provider places a tiny device, like a plug or coil, in or near the PAVM. This forces blood to take the proper path instead of going through the PAVM.
• Lung resection surgery: This is rare. You may need surgery if embolization isn’t possible — for example, if you have diffuse PAVMs or life-threatening bleeding. Providers may remove only the PAVMs or nearby lung tissue, too.
• Lung transplant: Receiving a new lung is a rare, last resort for diffuse PAVMs.

If you have HHT, you may need further treatments to manage other aspects of this condition. Your healthcare provider will help you understand each part of your care plan.

When should I see my healthcare provider?

Your provider will let you know how often you need follow-up visits and imaging tests. This follow-up care is key to managing your condition and reducing your risk of complications. PAVM monitoring is lifelong. That’s because it’s possible for PAVMs to form again even after treatment.

Contact your provider right away if you have new or changing symptoms.

What can I expect if I have this condition?

Your healthcare provider can explain what to expect based on your test results, symptoms and overall health. The effects of PAVMs vary from person to person. In general, embolization can improve symptoms in most people and significantly reduce the risk of serious complications, including stroke and infection in the brain.

Although embolization has excellent long-term success, some treated PAVMs can reopen over time, and new PAVMS may develop, especially in people with HHT. Regular follow-up imaging helps detect these changes, and repeat embolization can usually treat them successfully.

Is there anything I can do to feel better?

There are some things you can do in your daily life to reduce your risk of PAVM complications. You should always follow your healthcare provider’s advice, which is specific to your needs. But here are some general tips:

• Don’t smoke. Smoking harms your lungs in many ways. It also increases the risk that PAVMs will persist after treatment.
• Tell your dentist you have a PAVM. You need antibiotics before dental procedures. This lowers the risk of bacteria in your blood causing a brain abscess. It’s also important to see your dentist for routine cleanings and take extra good care of your teeth and gums at home.
• Talk to your provider about pregnancy. Pregnancy is high-risk when you have a PAVM. You need close monitoring and care throughout. Talk to your provider about the risks, ideally before getting pregnant.
• Avoid scuba diving. The sudden changes in pressure aren’t safe when you have a PAVM.

It’s also important to tell healthcare providers you have a PAVM before receiving IV medications or fluids.