Pulmonary Arteriovenous Malformation

What is Pulmonary Arteriovenous Malformation?

Pulmonary arteriovenous malformation (PAVM) is a rare lung condition where there’s an abnormal connection between the lung’s artery and vein. This leads to an unusual and harmful pathway of blood flow inside the lung from the right side to the left side. These conditions may also be referred to as pulmonary arteriovenous fistulae, aneurysms, or pulmonary hemangiomas. The connection between this lung condition and hereditary hemorrhagic telangiectasia (HHT), also known as Osler-Weber-Rendu syndrome, was first made over a century ago.

Many individuals with PAVMs don’t show symptoms but for those who go undiagnosed, serious complications could occur. These include stroke, heart attacks, brain abscesses, severe coughing up of blood and pooling of blood in the chest. Even though this condition doesn’t occur frequently, doctors need to consider PAVMs when patients complain of symptoms like nosebleeds, low oxygen levels in the blood or shortness of breath upon exertion. Understanding the origin, occurrence, signs and symptoms, evaluation, and treatment of this condition can provide useful insights for patients with PAVMs.

What Causes Pulmonary Arteriovenous Malformation?

Pulmonary arteriovenous malformations (PAVMs), which are abnormal connections between the arteries and veins in your lungs, can be present from birth or develop later in life. Most often, these are linked to a disease called Hereditary Hemorrhagic Telangiectasia (HHT). In fact, a significant majority of people – between 80 to 90% – who have PAVMs may eventually be diagnosed with HHT. Conversely, about 30 to 50% of individuals with HHT might also have PAVMs.

PAVMs can also occur independently of HHT, but that’s pretty rare. These cases are often associated with various health conditions like liver disease, chest surgery, trauma, parasitic infections, certain bacterial infections, heart valve disease, an inherited disorder that affects kidney function known as Fanconi syndrome, a liver condition related to liver disease called hepatopulmonary syndrome, and spread of cancer (metastatic carcinoma). PAVMs can also develop as a complication after surgery for heart defects in children. Besides, for some individuals, the cause may be unknown, which is referred to as idiopathic.

Risk Factors and Frequency for Pulmonary Arteriovenous Malformation

PAVMs, or Pulmonary Arteriovenous Malformations, are relatively rare. Detecting them can be difficult and varies based on the approach used for examination. They’re often hard to diagnose without detailed medical exams. For example, back in 1953, an autopsy study at Johns Hopkins Hospital may not have identified all cases, especially for small PAVMs that aren’t easily seen during routine reviews.

Further research, such as case studies from the Mayo Clinic, has given us a better idea of how often PAVMs occur. About 4.3 cases are identified each year at the Mayo Clinic. In addition, a large study that included over 21,000 chest CT scans showed that PAVMs struck about 1 in every 2,600 people.

• PAVMs are twice as common in women as in men.
• Most PAVMs (over 90%) are usually found on one side of the body and are singular.

PAVMs are often associated with a genetic disorder called HHT, or Hereditary Hemorrhagic Telangiectasia. This condition affects 1 in every 5,000 to 8,000 people and causes abnormal blood vessels to form in various parts of the body. About half of the people with HHT who also have PAVMs are women, and these vascular malformations are usually multiple and spread evenly throughout the lungs. Because of the strong link between HHT and PAVMs, doctors recommend screening for PAVMs in individuals diagnosed with HHT. This proactive approach can help doctors find these malformations early, manage them in time, and reduce health complications.

Signs and Symptoms of Pulmonary Arteriovenous Malformation

Most people with Pulmonary Arteriovenous Malformations (PAVMs) do not have symptoms and are usually discovered during chest scans or when screening for the related Hereditary Hemorrhagic Telangiectasia (HHT). However, for those who do have symptoms, they often start showing between the age of 40 and 60, while those with HHT may experience symptoms much earlier.

The most common symptom for those with HHT is nosebleeds, which happen because of bleeding from small blood vessels in the mucous membranes. Breathlessness is the second most common symptom, and it is especially common in patients with clubbed fingers or those with large or multiple PAVMs. Some patients can experience platypnea, which is a rare condition where breathlessness increases when standing up, but it is relieved when lying down.

One complication for PAVM patients can be coughing up blood – this happens when the PAVMs in the lung tissue or airways rupture, and this can be very serious. It’s important to check for PAVMs in patients who have unexplained breathlessness or low oxygen levels in their blood and in those who have lung abnormalities and a history of strokes or brain abscesses. These are common complications of PAVMs, often caused by a blood clot moving from the body to the brain (paradoxical embolization).

Other symptoms of PAVMs include: low oxygen levels in the blood, intolerance to exercise, chest pain, coughing, abnormal heart sounds, clubbed fingers, and bluish skin due to low oxygen. Symptoms can worsen in the third trimester of pregnancy due to increased blood volume, increased heart rate, and more flexible blood vessels – which lead to a greater blood flow through the PAVMs.

• Nosebleeds
• Breathlessness
• Platypnea (breathlessness that worsens with standing)
• Coughing up blood
• Low oxygen levels in the blood
• Exercise intolerance
• Chest pain
• Coughing
• Abnormal heart sounds
• Clubbed fingers
• Blue skin due to low oxygen
• Worsening symptoms during late pregnancy

One-third of PAVMs patients may also have orthodeoxia, wherein the oxygen levels in your blood drop by 2% or more when you stand up from lying down. Both orthodeoxia and platypnea can be symptoms of other conditions like liver-lung syndrome and atrial septal defects (holes in the heart).

Testing for Pulmonary Arteriovenous Malformation

If you have lung spots seen in X-ray images, a known or suspected diagnosis of a genetic disorder called Hereditary Hemorrhagic Telangiectasia (HHT), or unexplained symptoms like low blood oxygen level, shortness of breath, coughing up blood, bluish skin, changes to the shape of your fingers or toes, or sudden severe headache and vomiting, your doctor would want to investigate further. There are several easily-performed tests available to check for lung abnormalities known as Pulmonary Arteriovenous Malformations (PAVMs), such as studying the flow of your blood, lung scans and heart imaging. The most reliable test to diagnose PAVMs has traditionally been a lung x-ray where a special dye is injected into your blood vessels.

When you have PAVMs, more of your blood than normal (over 5%) bypasses the lungs and goes directly from the right side of your heart to the left. Your doctor can diagnose this by having you breathe in pure oxygen for 15 to 20 minutes and then measuring the oxygen in your blood. If more than 5% of your blood bypasses the lungs, your doctor will likely recommend further evaluation.

Chest X-rays are often the first step because they are easy, affordable, and use a low dose of radiation. However, they may miss smaller PAVMs, in which case more sensitive imaging would be needed for a more comprehensive evaluation.

The preferred screening test involves introducing a harmless saline solution into your blood and using ultrasound to track its flow through your heart. The appearance of bubbles in the left side of your heart would indicate the presence of PAVMs. This test also provides useful information about the risk of a future stroke or other serious conditions.

A lung scan can also be a helpful alternative. This test involves injecting a harmless radioactive protein into your blood and measuring how much bypasses the lungs and goes to your kidney. The lung scan cannot tell where else in the heart this could be happening, may be expensive, and is not available in all medical facilities.

A chest CT scan with a special dye is the preferred imaging test for confirming and visualizing the PAVMs. The CT scan often follows the saline solution test used to identify how much blood is bypassing the lungs. Especially in high-risk conditions or abnormal test results, and when the saline test shows lots of bubbles.

The choice to go for lung x-ray with a special dye, which traditionally has been considered the most reliable test for diagnosing PAVMs, often depends on the size of the feeding artery from the CT scan. If the artery has a diameter of 2 to 3 mm or more, your doctor may recommend a lung x-ray with a special dye. If you have specific symptoms, such as unexplained shortness of breath or low oxygen in your blood, you may still be referred for this test even if the artery is smaller.

If either the CT scan does not detect PAVMs but shunting is observed on saline ultrasound test, you may still need to have regular check-ups and repeat testing every 3 to 5 years. If the CT scan is not clear, further evaluation will depend on how high the suspicion is. You may need to go for lung x-ray with special dye if you have high-grade shunts. Otherwise, observation and follow-up scans, especially for those with mild symptoms or low-grade shunt, may be appropriate.

If you can’t have a lung x-ray with special dye, Contrast-enhanced magnetic resonance angiography (MRA), which can show the blood vessels in your lungs, may be used. However, this test can be expensive and is not usually readily available.

If you have a suspected or confirmed diagnosis of PAVM but have not been diagnosed with HHT, your doctor will pay special attention to your family and personal medical history and physical exam. They would recommend genetic testing when available and routine testing for family members. In families where HHT is known and one person has PAVMs, it is likely that about 35% will also have a PAVM. A negative screening result for HHT does not completely rule out the condition, especially if you have other known risk factors.

In conclusion, to diagnose if you have PAVMs, your doctor uses a combination of tests ranging from noninvasive methods, imaging studies and, when necessary, the most reliable test – lung x-ray with special dye. The choice of test largely depends on what is available and affordable, and your symptoms. Additionally, it’s also crucial to screen for HHT, especially in patients with a suspected or confirmed diagnosis of PAVM.

Treatment Options for Pulmonary Arteriovenous Malformation

The aim of treating Pulmonary Arteriovenous Malformations (PAVMs), air sacs in your lungs that help exchange gases between your blood and the air you breathe, is to stop complications such as brain infections and strokes, and decrease symptoms like difficulty breathing and low oxygen levels in the blood. The decision to start treatment depends on factors like your symptoms, the size of the feeding artery (the blood vessel supplying the PAVM), and whether you’re capable of going through the procedure.

It’s ideal for patients to be managed at specialized facilities like Hereditary Hemorrhagic Telangiectasia (HHT) centers, where experts in PAVM treatment can provide the most appropriate care, as each case has potential complexities.

Prioritizing treatment is dependent on factors like the presence of symptoms, the feeding artery diameter, and the patient’s ability to tolerate procedures. Asymptomatic patients, or those without symptoms and a feeding artery diameter less than 2 mm, might just need periodic medical monitoring, and CT scans every 5 to 10 years to check the PAVMs. However, for patients that do have symptoms, smaller lesions or a certain level of shunting, treatment is generally recommended. PAVMs with feeding artery diameter 3 mm or more as seen in chest CT scans should undergo pulmonary angiography for further evaluation.

One of the most effective treatments is Embolization therapy, where the feeding artery of the PAVM is blocked using coils or balloons. This restricts blood flow to the affected area. It’s often used for patients with symptoms or those with small lesions, particularly if associated with symptoms. It’s important to have follow-up imaging to confirm closure (successful blockage of the feeding artery).

Immediate benefits of embolization therapy include the stop of blood flow, relief from symptoms such as difficulty in breathing and improved oxygen levels in the blood. Long-term, it greatly reduces complications such as strokes and infections in the brain. Potential complications include chest pain, stroke, transient ischemic attack (a temporary neurological dysfunction due to lack of blood flow to the brain), and clinical embolization (introduction of air into the circulation, usually during the treatment). These risks would need to be weighed against the risks of untreated PAVMs.

With embolization therapy, follow-up is recommended 3 to 6 months post-procedure, with a contrast-enhanced chest CT and TTE (transthoracic echocardiogram which is an ultrasound of the heart) to confirm closure of the PAVMs. If a PAVM persists a year after initial treatment, repeat pulmonary angiography and transcatheter embolization are recommended. New or worsening pulmonary hypertension (high blood pressure in the lungs) can develop after embolization or extensive PAVM resection (surgical removal of the affected area).

There are also alternatives in case embolization therapy is not effective, although they are typically reserved for specific situations. Surgical excision, or removal, of the PAVM is recommended for patients where embolization therapy did not work or are experiencing life-threatening lung bleeds from ruptured PAVMs. Lung transplantation may be considered for severe cases, particularly patients resistant to repeated embolization procedures or with a high risk of dying, especially when involving both lungs (bilateral disease). This treatment is relatively uncommon and is often the last resort when other treatments have not been successful or feasible.

Supportive therapies for PAVMs might also be considered to complement primary treatments or manage symptoms. These include oxygen therapy to manage low oxygen levels, anticoagulation medications to prevent complications like stroke, and lifelong antibiotic prophylaxis (preventive treatment) before dental or surgical procedures even after embolization therapy to prevent infections in the blood and brain abscesses (collection of pus). Bevacizumab, a medication, has shown promise in decreasing the duration and number of epistaxis episodes (nosebleeds).

The treatment of PAVMs varies depending on factors like the presence of severe pulmonary hypertension (special caution may be required), management of pregnant women (consideration of safety measures and potential risk of PAVM to both mother and baby must be taken into account), administration of intravenous fluids or medications (considering the risk of air embolism), and lifestyle adaptations like not scuba diving due to the potential risks associated with PAVMs. Regular follow-up is important to monitor the effectiveness of the treatment and potential complications or the PAVMs returning.

What else can Pulmonary Arteriovenous Malformation be?

Pulmonary Arteriovenous Malformations (PAVMs) are rare and can cause numerous symptoms ranging from lung nodules, breathlessness, coughing up blood, stroke, and even brain abscess. They should be considered if more common causes of these symptoms have been ruled out.

Diagnosing PAVMs depends on the patient’s symptoms and their overall health context. Their breathlessness (dyspnea) could also be the result of other conditions such as liver-lung syndrome, abnormal openings between the heart’s chambers (atrial septal defects), and other conditions. Chest images and lung function tests can help narrow down the diagnosis.

Coughing up blood (hemoptysis) might be caused by blood vessel abnormalities in the nose (nasal telangiectases), bronchial tubes (endobronchial telangiectases), or PAVMs in the case of Hereditary Hemorrhagic Telangiectasia (HHT). PAVMs can cause severe bleeding, especially during procedures like biopsies; hence caution is necessary.

Shortness of breath when sitting up (platypnea) and low oxygen levels when lying down (orthodeoxia) often indicate liver-lung syndrome. However, vascular abnormalities in the heart can also cause these symptoms. CT scans can help to differentiate PAVMs from primary or metastatic lung and brain lesions, while a brain MRI is useful in differentiating between stroke, abscess, and AVMs in the brain.

Given the many symptoms and imaging results that mirror other diseases, we can group them into two categories when considering PAVMs: vascular lesions and nonvascular lesions.

Vascular lesions include:

• Unusual systemic vessels
• Vascular tissue growth (vascular parenchymal mass)
• Born or developed abnormal artery or veins (pulmonary varix)
• Pulmonary artery pseudoaneurysm
• Abnormal liver vessel (hepatopulmonary vessel)
• Retroperitoneal varices

Nonvascular lesions include:

• Bronchoceles
• Mucoceles
• Granulomas
• Lung collapse (atelectasis)
• Primary lung cancer
• Carcinoid tumor
• Metastatic disease

These classifications help to separate PAVMs from other conditions with similar presentations, guiding appropriate diagnostic and treatment considerations.

What to expect with Pulmonary Arteriovenous Malformation

PAVMs, or Pulmonary Arteriovenous Malformations, do not disappear on their own and mostly stay the same size. However, about 25% of them can get bigger at a small rate of 0.2 to 0.3 millimeters per year.

There’s no exact data on how many people get sick or die because of PAVMs, but it can lead to serious problems like strokes or brain abscesses, which are collections of infectious material in the brain. If a PAVM isn’t treated, it can lead to death in up to 50% of cases, compared to only 3% in people who get treatment.

Women who are at the second and third stages of pregnancy face an increased risk of PAVM rupture, which can cause complications such as hemothorax (blood in the space between the chest wall and the lung), hemoptysis (coughing blood), and dangerous bleeding in the lungs. Regular check-ups and prompt intervention are crucial in managing PAVMs and preventing severe complications.

Possible Complications When Diagnosed with Pulmonary Arteriovenous Malformation

Complications of PAVMs, also known as pulmonary arteriovenous malformations, often occur due to unusual clots traveling through the body. These may lead to serious brain problems such as stroke and brain abscesses, with higher risk in patients with more than one PAVM.

Here are some other commonly observed PAVM-related complications:

• Fainting (Syncope)
• Double vision (Diplopia)
• Ringing in the ears (Tinnitus)
• Migraine
• Headache
• Transient ischemic attack (temporary blockage of blood flow in the brain)
• Seizures
• Cerebral AVMs (abnormal blood vessels in the brain)
• Congestive heart failure
• Blood in cough (Hemoptysis)
• Hemothorax or pulmonary hemorrhage (blood in the chest or lungs)
• Heightened blood pressure in the lungs (Pulmonary hypertension)
• Anemia (decreased number of red blood cells or hemoglobin)
• Infective endocarditis (infection of the heart’s inner lining)
• Myocardial infarction (heart attack)

Preventing Pulmonary Arteriovenous Malformation

If you’re diagnosed with pulmonary arteriovenous malformations (PAVMs) – abnormal connections between your lung’s blood vessels – it’s critical that you undergo a detailed health checkup. This checkup is necessary because PAVMs could lead to severe health issues. The process would include studying your medical history, a physical examination and, if necessary, special genetic tests to rule out a condition called Hereditary Hemorrhagic Telangiectasia (HHT), a disorder which can cause blood vessels to form abnormally.

It’s important that the doctor discusses with you the specific signs, symptoms, and potential complications that could arise. This discussion is to help you understand and be prepared for what could happen. Regular follow-up appointments are highly recommended to closely monitor any changes or progression in your condition, or any possible complications that could come from any treatments received.