AV fistulas can occur due to a variety of factors. This article describes what they are, how they are caused, symptoms, diagnosis, and treatment.
What is an arteriovenous (AV) fistula?
An arteriovenous (AV) fistula is an abnormal link or connection between an artery and a vein. Normally, blood flows from an artery, into the capillaries, and then to the veins. This is important because the capillaries receive oxygen and nutrients from the artery and supply them to various tissues of the body. However, in this condition, the blood flows directly from an artery into a vein, bypassing the capillary. As a result, the affected tissues receive less oxygen and nutrients.
What causes an AV fistula?
Some causes include:
- Congenital: In some people, these are present from birth. This could be due to the improper development of arteries and veins during pregnancy
- Injuries: They can develop as a result of penetrating injuries, such as a stab wound or a gunshot
- Cardiac Catheterisation: If the needle used during cardiac catheterisation crosses both an artery and vein and causes the artery to get dilated, it can lead to the formation of an AV fistula
- Genetic conditions: Conditions such as Osler-Weber-Rendu disease are associated with the formation of AV fistulas in the lungs
- Surgically created AV fistulas: This is usually done in patients with chronic kidney disease or kidney failure. As these patients receive frequent dialysis, repeated needle insertions can scar and destroy their veins. Thus, AV fistulas are surgically created to make it easier to perform dialysis
What are the signs and symptoms of an AV fistula?
Some signs and symptoms include:
- Fatigue (this can happen if your tissues are not receiving an adequate blood supply)
- Swelling in your arms or legs
- Prominent, bulging veins that appear blue or purple in colour
- Decreased blood pressure
- Heart failure
In case the fistula is present in the lungs (pulmonary arteriovenous fistula), it can cause:
- Bluish discolouration of the skin
- Clubbing of your fingers (abnormal changes in your nail bed causing them to enlarge and become rounded and prominent)
- Coughing up of blood
Am I at risk for developing an AV fistula?
Some risk factors include:
- Older age
- Female sex
- Obesity
- High blood pressure
- History of cardiac catheterisation
- Medications such as blood thinners
When should I see a doctor?
What happens if I don’t treat my AV fistula?
Neglect or non-treatment can lead to serious complications such as:
- High-output heart failure: This happens because the heart is receiving more blood directly through the abnormal connection, causing it to work harder. Over time this can weaken your heart muscles and lead to heart failure, which presents as increased heart rate, palpitations, breathlessness, fatigue, cough and dizziness
- Blood clots: AV fistulas in the legs can lead to blood clots and deep vein thrombosis, a painful and potentially life-threatening condition
- Bleeding: In rare cases, there can be internal bleeding, particularly in the gastrointestinal system
How are AV fistulas diagnosed?
Your doctor will listen to the blood flow in the suspected area with a stethoscope. To confirm the diagnosis, they will prescribe some tests:
- Duplex ultrasound: This is the most common scan done to confirm the diagnosis. In this an instrument called a transducer is pressed against the skin over the suspected area which estimates the speed of the blood flow
- Computerised tomography (CT) angiogram: Through this procedure, your doctor can check if the blood flow is bypassing the capillaries. An iodine-rich contrast material is injected to check for the exact location of the fistula.
- Magnetic resonance angiography (MRA): This is done to detect deeply located fistulas
How are AV fistulas treated?
In the case of a small fistula that is not causing any symptoms, your doctor may suggest waiting and watching since these usually close spontaneously without treatment. However, if it is larger or causing symptoms, your doctor may recommend:
- Ultrasound-guided compression: An ultrasound-guided probe is used to compress the fistula and block blood flow to the damaged blood vessels. While simple, this procedure has comparatively low success rates
- Catheter embolisation: A catheter is inserted into an artery located near the AV fistula. Using X-ray and other imaging techniques this catheter is then guided to the site and a small coil or stent is placed to redirect your blood flow
- Surgery: For very large arteriovenous fistulas that cannot be treated with catheter embolisation, surgery is recommended
I have an artificially created AV fistula for haemodialysis. How can I care for it?
Follow this steps to ensure proper care:
- Always keep the access site clean
- Use the access site only for dialysis
- Avoid bumps or cuts at the access site
- Check the thrill (rhythmic vibration felt over the vascular access site)
- Watch out for signs of infection, such as redness, tenderness, or pus
- Check your blood pressure in the opposite arm
- Avoid wearing jewellery or tight clothes over the access site
- Do not lift heavy objects or put excessive pressure on the concerned arm
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