Cardiology > Arteriovenous Fistula

Background

An arteriovenous fistula (AVF) is an abnormal direct communication between an artery and a vein, bypassing the capillary bed. This results in altered hemodynamics, including decreased peripheral resistance and increased venous pressure and flow. AVFs can be congenital or acquired, and may be created surgically for hemodialysis access or occur due to trauma, aneurysm rupture, or iatrogenic interventions. 

II) Classification/Types

By Etiology: 

• • Congenital AVF: Present at birth; often part of syndromes like hereditary hemorrhagic telangiectasia. 

• • Acquired AVF: 

• • Iatrogenic: Most common, especially after catheterization or dialysis access creation. 

• • Traumatic: Penetrating injuries or blunt trauma. 

• • Aneurysm-related: Rupture of arterial aneurysms into adjacent veins. 

• • Neoplastic: Invasive tumors causing vessel erosion. 

By Location: 

• • Peripheral (e.g., radial-cephalic, femoral-saphenous) 

• • Central (e.g., aortocaval, pulmonary AVF) 

• • Cerebral (e.g., dural AVF) 

By Purpose (in iatrogenic cases): 

• • Therapeutic: Surgically created for hemodialysis access. 

• • Pathologic: Resulting in complications such as high-output cardiac failure or ischemia. 

III) Pathophysiology 

The fistulous connection allows arterial blood to bypass capillaries and flow directly into the venous system. This increases venous return and cardiac preload, often causing volume overload. Over time, large or high-flow AVFs may lead to: 

• • High-output heart failure 

• • Venous hypertension 

• • Distal ischemia due to “steal phenomenon” 

• • Aneurysmal dilation of the vein 

IV) Epidemiology

• • Sex: Slight male predominance, especially in trauma and ESRD populations. 

• • Age: AVFs for dialysis are common in patients aged 50–70 years with chronic kidney disease (CKD). 

• • Geography: Prevalence reflects access to vascular surgery and dialysis infrastructure. 

• • Comorbidities: Common in patients with end-stage renal disease, hypertension, or atherosclerosis. 

Etiology

I) Causes

• • Iatrogenic (vascular catheterization, dialysis access) 

• • Penetrating or blunt trauma 

• • Surgical procedures (e.g., biopsy, orthopedic surgeries) 

• • Congenital vascular malformations 

• • Ruptured aneurysms (e.g., iliac artery into iliac vein) 

• • Tumor invasion (e.g., renal cell carcinoma into IVC) 

II) Risk Factors

• • End-stage renal disease (requiring hemodialysis) 

• • Recent arterial or venous catheterization 

• • Trauma history 

• • Connective tissue disorders (e.g., Ehlers-Danlos) 

• • Aneurysmal disease 

• • Vascular surgery 

Clinical Presentation

I) History (Symptoms)

• • Localized AVF: Pulsatile mass, thrill, or bruit; limb swelling; venous engorgement 

• • Systemic symptoms (high-flow AVFs): 

• • Fatigue 

• • Worsening dyspnea or orthopnea (due to high-output heart failure) 

• • Palpitations 

• • Claudication or distal ischemia (steal syndrome) 

• • Dialysis AVF complications: Bleeding, infection, stenosis, aneurysm 

II) Physical Exam (Signs)

Vital Signs: 

• • Tachycardia 

• • Wide pulse pressure 

• • Possible signs of heart failure (e.g., peripheral edema) 

Local Findings: 

• • Palpable thrill over the AVF site 

• • Audible bruit 

• • Prominent superficial veins 

• • Limb swelling or ischemia (steal syndrome) 

Cardiac: 

• • Signs of volume overload: S3 gallop, displaced PMI 

Differential Diagnosis (DDx)

• • Aneurysm (without fistulous connection) 

• • Venous thrombosis 

• • Hemangioma 

• • Peripheral vascular disease 

• • High-output heart failure due to other causes (e.g., severe anemia, hyperthyroidism) 

• • Cellulitis or soft tissue mass 

Diagnostic Tests

Initial Tests: 

Duplex Ultrasound: 

• • First-line imaging 

• • Visualizes arterial inflow and venous outflow 

• • Detects turbulent high-velocity flow and confirms fistula anatomy 

CT Angiography (CTA): 

• • Defines size, location, and anatomy of AVF 

• • Essential in planning surgical or endovascular repair 

Magnetic Resonance Angiography (MRA): 

• • Useful alternative to CTA 

• • Avoids radiation and contrast in patients with CKD 

Echocardiogram: 

• • Assesses cardiac function in suspected high-output failure 

Right Heart Catheterization (select cases): 

• • Measures cardiac output in high-flow AVFs 

Treatment

I) Medical Management

Heart Failure Management: 

• • Diuretics to manage volume overload 

• • Afterload reducers (ACE inhibitors, ARBs) in high-output failure 

• • Beta-blockers for tachycardia 

Surveillance for Dialysis AVFs: 

• • Monitor access flow 

• • Education on infection prevention 

• • Prompt evaluation of complications (e.g., thrombosis, aneurysm) 

II) Interventional/Surgical

Endovascular Repair: 

• • Coil embolization or covered stents 

• • Ideal for deep or central AVFs (e.g., iliac, subclavian) 

Surgical Ligation or Repair: 

• • Indicated for large, symptomatic, or trauma-induced AVFs 

• • Preferred in accessible peripheral AVFs or failed endovascular therapy 

Dialysis Access Interventions: 

• • Balloon angioplasty for stenosis 

• • Surgical revision or creation of new AVF if thrombosed 

Patient Education, Screening, Vaccines

• • Educate on AVF site care and avoidance of compression/trauma 

• • Monitor for infection, swelling, or decreased bruit/thrill 

• • Avoid blood pressure measurement or venipuncture on AVF arm 

• • Limit heavy lifting with AVF limb 

• • Heart failure monitoring if symptomatic 

Vaccinations (especially in dialysis patients): 

• • Hepatitis B 

• • Influenza annually 

• • Pneumococcal vaccine 

• • COVID-19 vaccine 

Consults

• • Vascular Surgery: For AVF creation, repair, or complications 

• • Nephrology: Hemodialysis access planning and monitoring 

• • Cardiology: If high-output failure is suspected 

• • Interventional Radiology: Endovascular management 

• • Infectious Disease: For AVF-associated infection 

• • Primary Care/Internal Medicine: Chronic disease and risk factor management 

Follow-Up

• • Regular ultrasound surveillance for dialysis AVFs 

• • Monitor cardiac function in high-flow AVFs 

• • Reassess symptoms of ischemia or heart failure 

• • Education on AVF complications and early reporting 

• • Plan for AVF maturation or revision if needed