Arteriovenous fistula

Abnormal connection between an artery and a vein

An arteriovenous fistula (AVF) is an abnormal connection or passageway between an artery and a vein. It can occur naturally or be surgically created for medical purposes, such as for hemodialysis access. AVFs can lead to various complications if not managed properly.

Pathophysiology

An arteriovenous fistula involves a direct connection between an artery and a vein, bypassing the capillary system. This can result in altered blood flow dynamics, where blood flows directly from the high-pressure arterial system into the low-pressure venous system. This can lead to increased venous pressure, reduced perfusion of tissues, and potential cardiac overload due to increased venous return.

Causes

Arteriovenous fistulas can be congenital or acquired. Congenital AVFs are present at birth and may be part of vascular malformations. Acquired AVFs can result from trauma, surgical procedures, or diseases that affect the vascular system.

Congenital

Congenital AVFs are often part of complex vascular malformations and can occur in various parts of the body. They may be associated with syndromes such as Parkes Weber syndrome or Hereditary hemorrhagic telangiectasia.

Acquired

Acquired AVFs can result from:

• Trauma: Penetrating injuries or fractures can lead to the formation of an AVF.
• Surgical procedures: Intentional creation of AVFs for hemodialysis access.
• Inflammatory diseases: Conditions like vasculitis can damage blood vessels and lead to fistula formation.

Clinical Presentation

The symptoms of an arteriovenous fistula depend on its size, location, and the amount of blood flow through it. Common symptoms include:

• Swelling: Due to increased venous pressure.
• Bruit: A whooshing sound heard over the fistula due to turbulent blood flow.
• Warmth and redness: Over the area of the fistula.
• Heart failure: In large AVFs due to increased cardiac output.

Diagnosis

Diagnosis of an arteriovenous fistula typically involves:

• Physical examination: Detection of a bruit or thrill over the affected area.
• Imaging studies: Ultrasound, CT angiography, or MRI to visualize the fistula.
• Doppler studies: To assess blood flow dynamics.

Treatment

Treatment of an arteriovenous fistula depends on its cause, size, and symptoms. Options include:

• Observation: Small, asymptomatic AVFs may be monitored.
• Surgical repair: Ligation or resection of the fistula.
• Endovascular techniques: Use of coils or stents to occlude the fistula.

Complications

Complications of untreated arteriovenous fistulas can include:

• Heart failure: Due to increased cardiac output.
• Venous hypertension: Leading to edema and skin changes.
• Ischemia: Reduced blood flow to tissues distal to the fistula.

Related pages

• Hemodialysis
• Vascular malformation
• Heart failure
• Vasculitis

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