7 Key Symptoms of Arteriovenous Fistula You Should Know

An arteriovenous fistula (AVF) is an abnormal connection between an artery and a vein, bypassing the capillary system. This condition can occur naturally due to genetic factors or develop as a result of injury, surgery, or medical procedures. When an AV fistula forms, oxygen-rich blood flows directly from an artery into a vein, which can lead to various complications if left untreated. Understanding the symptoms of this condition is crucial for early detection and proper medical management.

While some arteriovenous fistulas are intentionally created for medical purposes such as dialysis access, others may develop spontaneously and cause significant health concerns. The severity of symptoms depends on the location and size of the fistula. Small AVFs may produce no noticeable symptoms, while larger ones can significantly impact your cardiovascular system and overall health.

1. Purplish or Bulging Veins

One of the most visible signs of an arteriovenous fistula is the appearance of purplish, bulging veins similar to varicose veins. These enlarged veins occur because the abnormal connection allows high-pressure arterial blood to flow directly into the low-pressure venous system.

The affected veins become distended and may appear rope-like or twisted beneath the skin’s surface. This symptom is particularly noticeable in superficial AVFs located close to the skin. The veins may feel warm to the touch due to the increased blood flow, and the overlying skin might appear discolored or take on a bluish-purple hue.

In some cases, these bulging veins can be tender or sensitive to pressure. The visibility of this symptom often depends on the location of the fistula—those in the extremities are typically more noticeable than those located deeper within the body or in internal organs.

2. Swelling (Edema)

Swelling in the affected area is a common symptom of arteriovenous fistula. This occurs because the abnormal blood flow pattern disrupts normal circulation, causing fluid to accumulate in the surrounding tissues. The swelling, medically known as edema, typically develops in the limb or body part where the AV fistula is located.

The edema associated with AVF can range from mild to severe. You may notice that the affected area appears puffy or enlarged, and the skin may feel tight or stretched. When you press on the swollen area, it might leave a temporary indentation, a characteristic known as pitting edema.

Progressive swelling can interfere with normal function and mobility, particularly when the fistula is located in an arm or leg. The swelling may worsen throughout the day and improve slightly with elevation of the affected limb. If the swelling becomes severe, it can lead to skin changes, including thinning, shininess, or increased susceptibility to injury.

3. Heart-Related Symptoms

An arteriovenous fistula can place significant strain on your cardiovascular system, leading to various heart-related symptoms. Because the fistula creates a shortcut in your circulatory system, your heart must work harder to pump adequate blood throughout your body.

Common cardiac symptoms include:

• Heart palpitations: You may experience a racing, pounding, or fluttering sensation in your chest as your heart attempts to compensate for the altered blood flow pattern.
• Shortness of breath: Difficulty breathing, especially during physical activity or when lying flat, can occur as the heart struggles to meet your body’s oxygen demands.
• Fatigue: Persistent tiredness and reduced exercise tolerance are common as your cardiovascular system becomes overworked.
• Chest discomfort: Some people experience chest tightness or pressure due to the increased cardiac workload.

In cases of large AVFs, the continuous high-volume blood flow can eventually lead to high-output heart failure if left untreated. This is why recognizing and addressing these cardiac symptoms early is essential for preventing serious complications.

4. A Machinelike Sound (Bruit) Over the Fistula

A distinctive characteristic of arteriovenous fistula is an abnormal sound called a bruit, which can be heard when a stethoscope is placed over the affected area. This machinelike, whooshing, or continuous humming sound results from the turbulent blood flow through the abnormal connection between the artery and vein.

Healthcare providers routinely listen for this sound when examining suspected AVFs, as it serves as an important diagnostic indicator. The bruit is typically continuous, though it may have a rhythmic quality synchronized with your heartbeat. The intensity and character of the sound can provide information about the size and flow rate through the fistula.

In some cases, particularly with superficial fistulas or very large AVFs, you might be able to feel a corresponding vibration or buzzing sensation when placing your hand over the area. This palpable vibration is called a thrill and represents the same turbulent blood flow that creates the audible bruit.

5. Decreased Blood Pressure Below the Fistula

When an arteriovenous fistula forms in a limb, it can cause reduced blood pressure in the portion of the limb located downstream from the fistula. This occurs because arterial blood is being diverted into the venous system before it can reach the tissues beyond the fistula.

This symptom may manifest as:

• Coolness in the affected extremity below the fistula location
• Pale or blanched skin appearance
• Numbness or tingling sensations
• Weakness in the affected limb
• Slow wound healing in the underperfused area

In severe cases, inadequate blood flow to tissues beyond the fistula can lead to ischemia, a condition where tissues don’t receive enough oxygen. This is particularly concerning in extremities and requires prompt medical evaluation to prevent tissue damage or loss.

6. Pain or Tenderness

Pain and tenderness in the area of an arteriovenous fistula are common symptoms that can significantly impact quality of life. The discomfort can result from several factors related to the abnormal vascular connection.

The pain associated with AVF may be characterized as:

• Aching or throbbing: A persistent dull ache or rhythmic throbbing sensation in sync with your pulse, caused by the increased pressure and volume in the affected vessels
• Sharp or stabbing: Sudden, acute pain that may indicate complications or rapid changes in the fistula
• Pressure-like discomfort: A feeling of heaviness or fullness in the affected area due to vascular engorgement

The tenderness is often most pronounced directly over the fistula site and may worsen with activity or pressure on the area. Some people experience increased pain after prolonged standing or use of the affected limb. The pain can also intensify if complications such as infection or thrombosis develop.

7. Skin Changes and Ulceration

Chronic arteriovenous fistulas can lead to significant changes in the skin overlying and surrounding the abnormal connection. These changes occur due to altered blood flow, increased venous pressure, and potential tissue ischemia in areas beyond the fistula.

Common skin manifestations include:

• Discoloration: The skin may become reddish, brownish, or take on a mottled appearance due to chronic venous congestion and hemosiderin deposition
• Thinning and fragility: The skin may become thin, shiny, and more susceptible to injury
• Dryness and scaling: Poor circulation can lead to dry, flaky skin that may itch or crack
• Ulceration: In advanced cases, open sores or ulcers may develop, particularly in areas with poor blood flow
• Warmth: The skin over the fistula often feels warmer than surrounding areas due to increased blood flow

These skin changes develop gradually over time and tend to worsen if the AVF remains untreated. Ulcers associated with arteriovenous fistulas can be particularly difficult to heal due to the underlying circulatory abnormality, and they carry a risk of infection. Any open wounds or persistent skin changes should be evaluated by a healthcare provider.

Main Causes of Arteriovenous Fistula

Understanding what causes arteriovenous fistulas can help in recognizing risk factors and seeking appropriate medical care. AVFs can be classified as either congenital (present at birth) or acquired (developing later in life).

Congenital Arteriovenous Fistulas

Some people are born with arteriovenous fistulas due to abnormal vascular development during fetal growth. These congenital AVFs result from errors in the formation of the circulatory system and may be associated with certain genetic syndromes or occur as isolated anomalies. Congenital fistulas may not become apparent until later in life as they grow or become more symptomatic.

Traumatic Injury

Penetrating injuries are a common cause of acquired AVFs. When a sharp object, bullet, or shrapnel pierces both an artery and adjacent vein, an abnormal connection can form as the wounds heal. Blunt trauma can also cause AVFs, though less commonly. Motor vehicle accidents, stab wounds, and gunshot injuries are typical scenarios that may result in traumatic arteriovenous fistulas.

Medical Procedures

Certain medical interventions can inadvertently create arteriovenous fistulas. Cardiac catheterization, where a catheter is threaded through blood vessels to the heart, carries a small risk of creating an AV fistula at the access site (typically in the groin or wrist). Similarly, biopsies, surgical procedures, or placement of central venous catheters can occasionally result in AVF formation.

Intentional Surgical Creation

Healthcare providers deliberately create arteriovenous fistulas, most commonly in the arm, to provide vascular access for patients requiring long-term hemodialysis. These surgical AVFs are created by connecting an artery to a nearby vein, causing the vein to become larger and stronger for repeated needle insertions during dialysis treatments.

Complications of Medical Conditions

Certain diseases can increase the risk of spontaneous AVF formation. Conditions that weaken blood vessel walls, such as Ehlers-Danlos syndrome or other connective tissue disorders, may predispose individuals to developing arteriovenous fistulas. Additionally, erosion from tumors or severe infections can rarely cause vessels to connect abnormally.

Prevention Strategies

While not all arteriovenous fistulas can be prevented, particularly congenital forms, several strategies can reduce the risk of acquired AVFs:

Minimize Trauma Risk

Taking safety precautions to avoid penetrating injuries can help prevent traumatic AVFs. This includes wearing appropriate protective equipment during high-risk activities, following workplace safety protocols, and practicing defensive driving to reduce motor vehicle accident risk.

Careful Medical Procedures

When undergoing medical procedures involving vascular access, ensure they are performed by experienced healthcare professionals using appropriate techniques. While complications can occur even with skilled practitioners, proper training and careful technique minimize the risk of inadvertent AVF creation.

Post-Procedure Monitoring

After any procedure involving arterial or venous access, monitor the site for signs of AVF formation, such as unusual swelling, continuous buzzing sensation, or abnormal sounds. Report any concerning symptoms to your healthcare provider promptly for early detection and intervention.

Management of Risk Factors

If you have a connective tissue disorder or other condition that weakens blood vessels, work with your healthcare team to manage the condition optimally. Regular monitoring and appropriate treatment can help reduce the risk of spontaneous vascular complications, including AVF formation.

Protective Care for Existing AVFs

For those who have intentionally created AVFs for dialysis access, proper care is essential to prevent complications. This includes keeping the area clean, avoiding tight clothing or jewelry over the site, not allowing blood pressure measurements or needle sticks on the arm with the fistula (except for dialysis), and promptly reporting any changes in the fistula’s appearance or function.

Frequently Asked Questions

How is an arteriovenous fistula diagnosed?

Diagnosis typically begins with a physical examination where your doctor listens for the characteristic bruit sound and feels for a thrill. Imaging studies such as ultrasound, CT angiography, or MR angiography can confirm the diagnosis and provide detailed information about the fistula’s location, size, and blood flow characteristics.

Can an arteriovenous fistula heal on its own?

Small AVFs occasionally close spontaneously, particularly those caused by minor trauma or medical procedures. However, most arteriovenous fistulas persist and may enlarge over time if left untreated. Medical evaluation is important to determine whether the fistula requires intervention or can be monitored.

Are arteriovenous fistulas dangerous?

The danger posed by an AVF depends on its size and location. Small fistulas may cause minimal problems, while large ones can lead to serious complications including heart failure, limb ischemia, or bleeding. AVFs in critical locations such as the brain or internal organs can be particularly serious and require prompt treatment.

What is the difference between an AV fistula and an AV malformation?

An arteriovenous fistula is a single abnormal connection between one artery and one vein. An arteriovenous malformation (AVM) is a more complex tangle of abnormal blood vessels involving multiple arteries and veins. AVMs are typically congenital, while fistulas can be either congenital or acquired.

Can I exercise with an arteriovenous fistula?

Exercise recommendations depend on the type, location, and size of your AVF. Those with surgical fistulas for dialysis are usually encouraged to exercise the affected arm to promote fistula maturation, following specific guidelines from their healthcare team. For other types of AVFs, your doctor will provide personalized advice based on your individual situation.

How long does it take for symptoms to appear after an injury?

Symptoms of a traumatic arteriovenous fistula may appear immediately after injury or develop gradually over weeks to months. Some small fistulas remain asymptomatic for years before being discovered incidentally or causing noticeable problems. The timeline varies based on the fistula’s size and location.

Is an arteriovenous fistula a type of blood clot?

No, an arteriovenous fistula is not a blood clot. It is an abnormal connection between an artery and vein. However, AVFs can increase the risk of blood clot formation in the affected vessels due to altered blood flow patterns. Conversely, blood clots can sometimes develop as a complication within an existing fistula.

Do all arteriovenous fistulas require treatment?

Not all AVFs require treatment. Small, asymptomatic fistulas that don’t affect heart function or tissue perfusion may simply be monitored over time. The decision to treat depends on factors including the fistula’s size, location, symptoms, impact on cardiovascular function, and risk of complications. Your healthcare provider will help determine the best approach for your specific situation.

References:

• Mayo Clinic – Arteriovenous Fistula
• Johns Hopkins Medicine – Arteriovenous Fistula
• National Heart, Lung, and Blood Institute – Arteriovenous Fistula
• National Center for Biotechnology Information – Arteriovenous Fistula
• Radiological Society of North America – Arteriovenous Fistula