Arteriovenous Fistula

An arteriovenous (AV) fistula is an unusual connection between an artery and a vein. Normally, blood travels from arteries through tiny blood vessels called capillaries to veins. This journey is how the body's tissues get the nutrients and oxygen they need.

In an AV fistula, blood takes a shortcut, flowing directly from the artery to the vein. This bypasses the capillaries. As a result, the tissues that rely on the skipped capillaries don't get as much blood, nutrients, and oxygen as they should.

Small connections between arteries and veins (arteriovenous fistulas) in the legs, arms, lungs, kidneys, or brain are often unnoticed. These small fistulas usually don't need any special treatment, just regular checkups with a doctor.

However, larger fistulas can cause problems. Signs and symptoms of an arteriovenous fistula can include:

• Visible, bulging, purplish veins: These might look similar to varicose veins, but they're different. The veins might be more noticeable because of the abnormal blood flow.
• Swelling in the arms or legs: Extra fluid can build up in the affected area due to the altered blood flow.
• Low blood pressure: The fistula can interfere with the body's ability to regulate blood pressure.
• Feeling tired or weak (fatigue): The body might be working harder to compensate for the abnormal blood flow.
• Heart problems (heart failure): In some cases, a large fistula can strain the heart, leading to heart failure.

A large fistula in the lungs (pulmonary arteriovenous fistula) is a more serious concern. It can lead to:

• Bluish or grayish discoloration of the lips and fingernails (cyanosis): This happens because not enough oxygen-rich blood is reaching these parts of the body.
• Rounded, swollen fingertips (clubbing): This is a sign of long-term low oxygen levels.
• Coughing up blood (hemoptysis): Blood in the cough is a serious symptom.

A fistula in the digestive tract can cause bleeding in the stomach or intestines (gastrointestinal bleeding). This can lead to symptoms like stomach pain and vomiting blood.

In short, while small arteriovenous fistulas may not cause any problems, larger ones can lead to a range of symptoms, some of which can be serious. Regular checkups and prompt medical attention are important if you experience any of these signs.

If you notice any signs or symptoms of an arteriovenous fistula (AVF), schedule a visit with your doctor. Catching an AVF early can often make it easier to treat. Early diagnosis also helps lower the chances of problems like blood clots or heart failure.

Arteriovenous fistulas (AVFs) can happen in two ways: some are present from birth (congenital), while others develop later in life (acquired). Here's what can cause them:

• Physical injury: If a wound, like a gunshot or stab wound, goes through the skin and hits a vein and artery close together, it can create an AVF. Think of it like a connection being made between the blood vessels that shouldn't be there.

• Birth defects (congenital AVFs): Sometimes, during pregnancy, the arteries and veins in a baby don't form correctly. Doctors aren't always sure why this happens.

• Inherited conditions: AVFs, especially in the lungs (pulmonary AVFs), can be linked to certain genetic conditions. These conditions cause unusual blood vessel growth, often leading to problems throughout the body, particularly in the lungs. One example is Osler-Weber-Rendu syndrome, which is also known as hereditary hemorrhagic telangiectasia. This means the condition is passed down through families.

• Kidney dialysis: For people with severe kidney disease needing dialysis, a surgeon might create an AVF in their forearm. This makes it easier and more efficient to access the blood vessels for the dialysis procedure. Essentially, a planned connection is made between an artery and a vein to improve access for the dialysis treatment.

Some people are born with certain health conditions that make them more likely to develop arteriovenous fistulas (AVFs). These are abnormal connections between arteries and veins. There are other things that can raise the chances of getting an AVF, too.

Factors that increase the risk of AVFs include:

• Being older: As you get older, your risk generally increases.
• Being female: Women tend to have a slightly higher risk than men.
• Having a cardiac catheterization: This is a medical procedure where a thin tube is inserted into a blood vessel. If the procedure is done in the groin area, this increases the risk. This is because the groin area is a place where blood vessels are close together, making it easier for an AVF to form.
• Taking certain medicines: Some blood thinners (anticoagulants) and medicines to stop bleeding (antifibrinolytics) can raise the risk of AVFs. This is because these drugs can make the blood vessels more prone to bleeding and damage.
• High blood pressure: Having high blood pressure can stress the blood vessels and make them more vulnerable to problems like AVFs.
• High body mass index (BMI): Having a higher BMI (a measure of body fat based on height and weight) may also slightly increase the chance of developing an AVF. This is likely due to the higher pressure on blood vessels from excess weight.

An arteriovenous fistula, if left unmanaged, can lead to several problems. Some of these complications can be serious.

• Heart Trouble (Heart Failure): A fistula lets blood rush through it faster than normal blood vessels. This faster flow puts extra work on the heart, making it pump harder. Over time, this extra strain can cause the heart to weaken and fail to pump effectively. This is a serious problem. Large fistulas are more likely to cause this.

• Blood Clots: A fistula in the leg can sometimes cause blood clots to form. These clots can be dangerous. If a blood clot breaks off and travels to the lungs, it can be life-threatening (called a pulmonary embolism). Blood clots can also form in other areas, potentially leading to a stroke if the clot travels to the brain.

• Leg Pain (Claudication): A fistula can sometimes block the blood supply to the muscles in the legs. This lack of blood flow can cause pain when walking or exercising (claudication). It's like your muscles aren't getting enough oxygen.

• Internal Bleeding: Fistulas can sometimes cause bleeding inside your body, potentially affecting your stomach or intestines. This can be a dangerous complication.

Doctors use several methods to find arteriovenous fistulas (AVFs). An AVF is an abnormal connection between an artery and a vein. One simple way to potentially detect an AVF is by listening to the blood flow in your arms and legs with a stethoscope. A rushing or humming sound might indicate an AVF.

If a doctor suspects an AVF, they'll likely order more tests to confirm the diagnosis. These tests help them see the blood flow more clearly.

• Duplex Ultrasound: This is a common and often the first test used. It uses sound waves to map the speed and direction of blood flow in your arteries and veins. This helps the doctor see if blood is flowing unusually quickly or in an unusual pattern, which could suggest an AVF.

• CT Angiogram: This test uses X-rays and a special dye (contrast) injected into your veins. The dye makes blood vessels stand out more clearly on the images. The CT scan can show the entire body, including blood vessels, and help determine if blood is flowing directly from an artery to a vein, bypassing the tiny blood vessels (capillaries) in between. This is important because it helps pinpoint the location and severity of the AVF.

• MRA (Magnetic Resonance Angiography): Similar to a regular MRI, an MRA uses powerful magnets and radio waves to create detailed images of blood vessels. It also uses a special dye (contrast) to highlight the blood vessels. Doctors may use an MRA if the AVF is suspected to be deeper under the skin, where it might be harder to see with other tests. MRA gives doctors a more detailed picture of the blood vessels in the area.

Small arteriovenous fistulas (AVFs) that aren't causing other health problems often only need regular checkups by a doctor. Sometimes, these small AVFs will heal on their own.

However, if an AVF needs treatment, there are several options your doctor might suggest:

• Ultrasound-guided compression: This is a good choice for AVFs in the legs that are easy to see with an ultrasound machine. A special probe is used to press on the AVF for about 10 minutes. This pressure stops blood flow to the abnormal blood vessels, effectively closing the fistula.

• Catheter embolization: A thin, flexible tube (a catheter) is inserted into an artery near the AVF. A small coil or a tiny scaffold-like structure (a stent) is then placed at the site of the fistula. This redirects the blood flow away from the abnormal connection. Most people who have this procedure are able to go home the same day or the next, and they can usually return to their normal routine within a week.

• Surgery: Larger AVFs that can't be treated with catheter embolization might need surgery. The specific type of surgery will depend on how big the AVF is and where it's located. The surgeon will choose the best approach to address the abnormal connection and restore normal blood flow.

Essentially, the best treatment for an AVF depends on its size, location, and whether it's causing other problems. Your doctor will discuss the best option for you.