Definition of Arteriovenous Fistula
Arteriovenous fistula is an abnormal channel that sits between an artery and a vein. Under normal circumstances the blood flows from arteries to capillaries and then to veins. In an arteriovenous fistula, the blood flows directly from arteries to veins without passing through capillaries.
Causes of Arteriovenous Fistula
Arteriovenous fistula may be congenital abnormalities (congenital fistula) or can occur after birth (acquired fistula). Congenital arteriovenous fistula is rare. Acquired arteriovenous fistula can be caused by a variety of injuries that damage the arteries and veins that are close together, especially penetrating injuries due to knife or bullet. Fistulas can occur immediately or several hours later emerging. If blood seeps into the surrounding tissue, the injured area will experience immediate swelling.
Every time conducted several medical treatments (eg renal dialysis) required its way into the blood vessels (veins). This causes repeated stabbing veins become inflamed and can cause blood clots, and eventually the vein will be clogged by scar tissue. To avoid this, deliberately created arteriovenous fistula, usually between adjacent veins and arteries in the arm. This will widen the veins, facilitate the entry of the needle and reduce the chances of blood clots because blood flows faster. This small fistula does not cause heart defects and can be closed when not needed anymore.
Symptoms of Arteriovenous Fistula
If the congenital arteriovenous fistula located close to the skin surface, it would appear reddish blue swelling. In obvious places (eg faces), fistula will appear purplish. If a large arteriovenous fistula obtained untreated, a large amount of blood will flow under high pressure from the arteries to the veins. Vein wall is not strong enough to withstand this high pressure, so the walls are stretched and widened and prominent veins (varicose veins sometimes resemble).
Flow back to the heart through the abnormal arteriovenous shortcuts can make tense heart, causing heart failure. The larger the fistula, the faster heart failure.
Diagnosis of Arteriovenous Fistula
With a stethoscope placed over a large arteriovenous fistula obtained, could be heard the sound back and forth, such as moving machinery (machinery murmur). To confirm the diagnosis and to determine the extent of abnormality, angiography performed. At angiography injected a dye into the blood vessels and seen on x-rays; dye will show the pattern of blood flow.
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