Arteriovenous (AV) fistula

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Generally, blood flows from your heart to all areas in the body through large arteries. The arteries travel until they become capillary, which is a single cell thick.

This capillary bed is the place where the blood interchanges oxygen and nutrients with the tissues of your body and picks up the waste. The blood travels back to the heart from the capillary bed through veins. The capillary bed is the meeting point of an artery and vein.

In an arteriovenous malformation (AVM) a group of blood vessels forms incorrectly in your body. These malformations of arteries and veins are tangled forming direct connections, bypassing the capillary bed.

Veins are small and might not be able to control the pressure of the blood that directly comes from the arteries. This leads to high-pressure shunt or fistula.

The extra blood forces the veins to stretch and enlarge. The weak spots in the blood vessels may rupture and bleed. Most likely they might result in aneurysms. Usually, this happens at the time of fetus development before or shortly after birth. An arteriovenous (AV) fistula is a similar condition to an AVM. There are various types of AVMs:

  • Arteriovenous malformation
  • Cavernoma
  • Venous malformation
  • Capillary telangiectasia
  • Dural AV fistula

AVMs can develop anywhere in the body where arteries and veins are present. For instance, brain AVMs that occur on the surface or deep in the brainstem, and within the dura membrane. Spinal AVMs may develop on the surface or within the spinal cord.

Arteriovenous (AV) Fistula

AV fistula is fully termed as arteriovenous fistula develops as a result of an abnormal connection of an artery and a vein. Usually, blood flows from the arteries to capillaries and then into the veins. The nutrients and oxygen in your blood travel from these capillaries to your body tissues.

But with an AV fistula, your blood travels directly from the artery into a vein bypassing the capillary. In this condition, the tissues under the bypassed capillaries get less blood supply.

Arteriovenous fistulas mostly happen in your arms and legs but can develop in any place in the body. Often, AV fistulas are created surgically for dialysis in people suffering from severe kidney diseases.

Symptoms Arteriovenous (AV) Fistula

Small arteriovenous fistulas that occur in your legs, forearm, lungs, kidneys, or brain might not show any signs or symptoms, and normally treatment is also not required other than monitoring.

But large arteriovenous fistulas might cause some signs and symptoms, which include:

  • Bulging veins that can be see through your skin and appears like varicose veins
  • Purplish colour skin at the affected site
  • A rise in skin temperature
  • hypotension – decreased blood pressure
  • Swelling in your arms or legs
  • Fatigue
    Heart failure

If an arteriovenous fistula occurs in your lungs, it is called a pulmonary arteriovenous fistula. It is a serious health condition which causes the symptoms:

  • A bluish shade on the skin
  • Clubbed fingers (the tips of finger spread out and become round)
  • Blood when coughing

The symptoms of arteriovenous fistula vary based on your body part affected. If it occurs in your gastrointestinal tract, it can cause bleeding in the digestive tract.

If you observe the above symptoms, it’s better to consult a doctor immediately. Early diagnosis and treatment for arteriovenous fistula might reduce your risk of complications, including blood clots, bleeding, or heart failure.

Causes Of Arteriovenous (AV) Fistula

The exact cause of arteriovenous(AV) fistula is yet to be known. It might be congenital or acquired, sometimes connected with other conditions like hypertension (high blood pressure).

Injuries that pierce your skin, such as a stabbing, accidents on your body part at the vein and artery site, are located side by side.

Congenital disabilities: some babies are born with this condition because the arteries and veins may not develop in the womb.

Genetic conditions: Pulmonary arteriovenous fistulas can be formed by a genetic disease called Osler-Weber-Rendu or hereditary hemorrhagic telangiectasia. The condition causes your blood vessels to be malformed throughout your body, particularly in your lungs.

AV fistula is also created surgically in people with late-stage kidney failure. It helps to perform Hemodialysis dialysis easily.

Risk factors Of AV Fistula

Along with certain genetic disorders and congenital conditions, the below risk factors can make you more prone to arteriovenous fistula:

  • AV fistula is more prevalent in female
  • Certain medications which include anticoagulants(blood thinners) and
  • anti-fibrinolytic (used to control bleeding)
  • High blood pressure
  • High BMI
  • Increasing age

How To Diagnose AV Fistula?

If you are suspected of having an AV fistula, you need to undergo some tests to confirm your diagnosis. The diagnosis tests are as follows:

  • Physical Examination is done to monitor BP, heart rate, and distal pulse.
  • Doppler ultrasound to evaluate the blood flow in your blood vessels.
  • Magnetic Resonance Imaging (MRI) to find any abnormalities present.
  • Catheter Angiography: a tube called a catheter is inserted into the blood vessel to find the abnormalities.

Treatment For Arteriovenous (AV) Fistula

If the arteriovenous(AV) fistula is small, you might be monitored closely by the doctor because some AV fistulas are fixed on their own without treatment. If the arteriovenous(AV) fistula is large and causing discomfort, it requires treatment, and your doctor might suggest:

Endovascular Embolization: often termed as catheter endovascular embolization is the most common treatment option for treating AV fistulas. It is a minimally invasive surgical procedure that helps t block abnormal vascular channels.

The procedure is done by a specially trained interventional radiologist which involves inserting a thin tube called a catheter into your artery from the groin area.

A fluoroscopic or X-ray imaging technique is used to reach the location of the fistula. A small coil or liquid embolic agents are sent through the catheter and placed at malformation to stop the blood flow to the fistula.

The recurrence rate of fistula formation after this treatment is very less.

Sclerotherapy: In this procedure, sclerosant – a liquid medicine is injected into the veinous malformations to shrink or destroy the damaged vessels. This procedure also helps to minimize or stops the blood flow into the AVMs.

Sclerotherapy is also used in the treatment of venous malformations and lymphatic malformations. During this procedure, a radiologist uses ultrasound and X-ray imaging technique to reach the malformations.

Sclerotherapy can be used as an alternative treatment method for venous malformations. It is used to decrease the lesion size, before surgery to support surgery or to prevent post-operative complement.

Different sclerosants like chemical agents, osmotic agents and detergents to destroy the vascular malformations.

Stereotactic Radiosurgery (SRS): Among all available treatment procedures, stereotactic radiosurgery for AV fistula is a safe and effective modality. SRS is mostly preferred if a fistula is formed close to brain structures. SRS is a painless and outpatient procedure performed radiologist in the radiation oncology lab.

A stereotactic head frame is positioned on to the fistula area, then a high-intensity X-rays are precisely focused to block the malformation in your blood vessels.

The treatment procedure is similar to a CT scan and might lasts around 30 minutes. It is preferred over traditional surgery because it is a minimally invasive surgery and doesn’t affect your surrounding tissues.

Surgery: Large arteriovenous fistulas might require surgery because catheter embolization might not be effective enough. The surgeon makes large incisions to reach the malformation.

After the surgeon gets access to fistula, the irregular arteries and veins are eliminated and redirect blood flow, preventing the artery malformations from leaking or bursting.

However, the type of surgery depends on the AV fistula size and its location.
If you suspect to have an arteriovenous fistula, consult Dr. Pradyumna Reddy, one of the best interventional radiologist doctors in Hyderabad. He has more than five years of experience in AV fistula through embolisation and sclerotherapy.

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