What is an Arteriovenous Fistula?

Arteriovenous (AV) fistula is a potentially serious condition characterized by abnormal arterial and vein formation. Treatment for this condition is dependent on the location and size of the fistula. Complications associated with AV fistula formation include blood clot formation and heart failure.

Within the circulatory system, blood flows through an established path consisting of arteries, capillaries, and veins. Sequentially, the blood begins its journey in the artery and passes through a capillary before reaching its intended vein. In the presence of arteriovenous fistula, an individual’s blood skips passage through the capillary and goes directly to the vein. These small vessels normally serve to supply the body's tissues with oxygenated blood; therefore, when the capillaries are deprived of blood and nutrients, so are their related tissues.

Arteriovenous fistula is a condition that may be congenital, meaning it is present at birth, or it may be acquired. When an AV fistula is diagnosed as being a congenital condition, it is generally more pronounced within the lungs and results from the presence of a secondary condition, such as Rendu-Osler-Weber disease (ROWD). Individuals who have undergone surgical procedures, such as a heart catheterization, may develop an AV fistula as a complication. The occurrence of deep puncture wounds, such as that sustained with a gunshot, may also contribute to AV fistula formation. An arteriovenous fistula may also be artificially created for treatment purposes, as is sometimes necessary with dialysis.

Individuals who develop an AV fistula in their limbs often remain asymptomatic, meaning they experience no symptoms at all. Asymptomatic individuals generally require no treatment and experience no further complications. Those who develop more prominent fistulas that are larger in size tend to experience various, persistent signs and symptoms.

Oftentimes, if the fistula is located in one’s limbs, she or he may develop swelling in the affected appendage. The skin in the affected area may also adopt a ruddy hue or demonstrate veinous bulging. When an AV fistula develops in the lungs, symptoms manifest differently and can lead to life-threatening complications.

Individuals with a pulmonary arteriovenous fistula may experience shortness of breath, frequent nosebleeds, and, occasionally, may cough up blood. Due to the oxygen deprivation that often occurs with this form of fistula, an individual may develop cyanosis, which is a bluish hue to the skin. Additionally, individuals with a pulmonary arteriovenous fistula may also be at an increased risk for heart valve infections, such as mitral valve stenosis.

There are several diagnostic tests that may be performed to diagnose an arteriovenous fistula. During a physical examination, a physician will listen to the individual’s heart to determine if any abnormalities exist, such as a humming sound which often occurs in the presence of an arteriovenous fistula. If a humming or other abnormality is detected, the individual is usually referred for additional testing. Imaging tests, such as a computerized tomography (CT) angiogram and Doppler ultrasound, may be performed to evaluate blood flow through the individual's arteries and confirm the presence of an arteriovenous fistula.

For many individuals with an AV fistula, treatment consists of monitoring their condition for any changes. Those whose AV fistula is large may undergo a procedure known as a catheter embolization, which involves the insertion of a stent, made of synthetic material, to bypass blood flow around the fistula. Arteriovenous fistulas that cannot be treated with stent placement may necessitate further corrective, surgical measures. Surgical approach is wholly dependent on the location and size of the fistula and the overall health of the individual.