An arteriovenous fistula is an abnormal communication between an artery and a vein.
An arteriovenous fistula may be congenital (usually affecting smaller vessels) or acquired as a result of trauma (eg, a bullet or stab wound) or erosion of an arterial aneurysm into an adjacent vein. In patients with end-stage renal disease requiring hemodialysis, an arteriovenous fistula is created surgically to provide vascular access for the procedure.
The fistula may cause symptoms and signs of
Arterial insufficiency (eg, ulceration due to reduced arterial flow or ischemia)
Chronic venous insufficiency due to high-pressure arterial flow in the affected veins (eg, peripheral edema, varicose veins, stasis pigmentation)
Emboli may pass from the venous to the arterial circulation (and cause ulceration when they lodge in distal vessels), although pressure differences make this unlikely. If the fistula is near the surface, a mass can be felt, and the affected area is usually swollen and warm with distended, often pulsating superficial veins.
A thrill can be palpated over the fistula, and a continuous loud, to-and-fro (machinery) murmur with accentuation during systole can be heard during auscultation.
Rarely, if a significant portion of cardiac output is diverted through the fistula to the right heart, high-output heart failure develops.
Diagnosis of Arteriovenous Fistula
Clinical evaluation
Sometimes ultrasonography
Fistulas are diagnosed clinically based on presence of thrill, murmur, and other signs.
Doppler ultrasonography is the best confirmatory test. For fistulas that cannot be visualized with ultrasonography, magnetic resonance angiography (MRA) or computed tomography angiography (CTA) may be used. Imaging with conventional angiography is typically done when a catheter-based treatment is planned.
Treatment of Arteriovenous Fistula
Sometimes percutaneous occlusion techniques
Sometimes surgery
Congenital fistulas do not require treatment unless significant complications develop. When necessary, percutaneous vascular techniques can be used to place coils or plugs into the vessels to occlude the fistula. Treatment is often effective but recurrent bleeding can still occur, especially in other locations.
Acquired fistulas usually have a single large connection and can be effectively treated by surgery.
