What Is an Arteriovenous Fistula

An arteriovenous (AV) fistula is an abnormal connection between an artery and a vein. This connection prevents blood from flowing from the artery to the capillaries, which are meant to supply oxygenated blood to the body’s various tissues before the blood passes into the veins.

Because of an AV fistula, arterial blood flows directly into the vein without reaching the capillaries, leading to a lack of blood supply in certain tissues.

An arteriovenous fistula can occur due to various causes, including:

• Skin ruptures from puncture wounds that affect veins adjacent to arteries.
• Congenital abnormalities.
• Hereditary hemorrhagic telangiectasia.

Potential risk factors for developing the condition include:

• High blood pressure.
• Overweight and obesity.
• Being a senior citizen.
• Being female.
• Having undergone cardiac catheterizations.
• Taking anticoagulants.
• Using antifibrinolytics.

Although arteriovenous fistulas appear most frequently in the lower limbs, they can occur in any area of the body. There are also fistulas surgically created to help the dialysis process in patients with kidney failure.

In serious cases, it’s important to diagnose and treat it promptly because it can lead to severe complications such as:

• Deep vein thrombosis.
• Heart failure.
• Permanent pain.
• Hemorrhages.

The presence of an AV fistula can go unnoticed in its initial stages. However, as the communication between veins and arteries is affected and blood flow changes, signs and symptoms begin to appear. These vary depending on the size and location of the fistula.

Fistulas in the Arm and Leg

When an arteriovenous fistula develops in the limbs, symptoms are usually related to the abnormal increase in blood flow and the overload on the veins.

The skin near the affected area often shows visible redness. The veins may also appear dilated or feel palpable, and an unusual pulse or a bruit (a specific sound heard with a stethoscope) may be felt due to the turbulent blood flow.

The patient may also experience swelling, a sensation of local warmth, and pain or cramps that worsen with physical activity.

If the fistula is large or not treated properly, it can lead to limb fatigue, muscle weakness, and trophic changes in the skin, meaning the development of ulcers or discoloration due to poor oxygen supply to the tissues.

Pulmonary Fistulas

Pulmonary arteriovenous fistulas cause blood to pass directly from the pulmonary arteries to the veins without proper oxygen exchange in the capillaries.

This situation causes deficient oxygenation, which generally manifests as shortness of breath, especially during physical exertion. Fatigue, dizziness, and cyanosis—a bluish discoloration of the lips, nails, or skin—also often develop due to hypoxemia.

In more advanced cases, or where there are large fistulas, coughing with blood (known as hemoptysis), chest pain, and episodes of migraines or neurological symptoms may occur. This is because unfiltered blood can allow microemboli to pass into the brain.

For all these reasons, early detection is crucial to prevent serious events, including the development of a stroke.

The diagnosis of an arteriovenous fistula begins with a clinical history and a physical examination. During the exam, the doctor may detect characteristic signs like a bruit or a palpable vibration in the affected area.

Visual inspection can also help in some cases by revealing dilated veins, changes in skin color, and signs of local circulatory insufficiency.

If the fistula is internal, both the patient’s symptoms and medical history help guide the suspicion, but imaging studies will be necessary to reach a definitive diagnosis.

Doppler ultrasound is one of the most frequently used tests as it allows for the visualization of blood flow and its direction. Angiography is also employed, providing a detailed image of the abnormal connection between arteries and veins.

MRI and CT scans are useful for locating deep fistulas or those in internal organs.

Specifically for pulmonary fistulas, oximetry and arterial blood gas analysis help identify alterations in oxygenation.

The treatment for an arteriovenous fistula depends on its location, size, and the symptoms it causes.

If it’s a small fistula that is asymptomatic and carries no risk of complications, your doctor may recommend only periodic monitoring and follow-up with check-ups and imaging studies.

However, regardless of its size, if a fistula causes symptoms or compromises the function of an organ or poses a risk of serious complications, intervention is necessary.

Treatment options include open surgery to repair or close the abnormal connection. Minimally invasive procedures such as endovascular embolization can also be performed, which uses catheters to block the flow in the fistula. Sometimes, the use of stents or vascular grafts may be required to restore normal blood flow.

Early treatment is key to preventing irreversible tissue damage and systemic complications.

At the  Vascular, Arterial, and Venous Disease  area of Centro Médico ABC, we can provide you with specialized care. Contact us!