arteriovenous fistula

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Arteriovenous Fistula

 

Definition

An arteriovenous fistula is an abnormal channel or passage between an artery and a vein.

Description

An arteriovenous fistula is a disruption of the normal blood flow pattern. Normally, oxygenated blood flows to the tissue through arteries and capillaries. Following the release of oxygen in the tissues, the blood returns to the heart in veins. An arteriovenous fistula is an abnormal connection of an artery and a vein. The blood bypasses the capillaries and tissues, and returns to the heart. Arterial blood has a higher blood pressure than veins and causes swelling of veins involved in a fistula. Although both the artery and the vein retain their normal connections, the new opening between the two will cause some arterial blood to shunt into the vein because of the blood pressure difference.

Causes and symptoms

There are two types of arteriovenous fistulas, congenital and acquired. A congenital arteriovenous fistula is one that formed during fetal development. It is a birth defect. In congenital fistulas, blood vessels of the lower extremity are more frequently involved than other areas of the body. Congenital fistulas are not common. An acquired arteriovenous fistula is one that develops after a person is born. It usually occurs when an artery and vein that are side-by-side are damaged and the healing process results in the two becoming linked. After catheterizations, arteriovenous fistulas may occur as a complication of the arterial puncture in the leg or arm. Fistulas also form without apparent cause. In the case of patients on hemodialysis, physicians perform surgery to create a fistula. These patients receive many needle sticks to flush their blood through dialysis machines and for routine blood analysis testing. The veins used may scar and become difficult to use. Surgery is used to connect an artery and vein so that arterial blood pressure and flow rate widens the vein and decreases the chance of blood clots forming inside the vein.
The main symptoms of arteriovenous fistulas near the surface of the skin are bulging and discolored veins. In some cases, the bulging veins can be mistaken for varicose veins. Other fistulas can cause more serious problems depending on their location and the blood vessels involved.

Diagnosis

Using a stethoscope, a physician can detect the sound of a pulse in the affected vein (bruit). The sound is a distinctive to-and-fro sound. Dye into the blood can be tracked by x ray to confirm the presence of a fistula.

Treatment

Small arteriovenous fistulas can be corrected by surgery. Fistulas in the brain or eye are very difficult to treat. If surgery is not possible or very difficult, injection therapy may be used. Injection therapy is the injection of substances that cause the blood to clot at the site of the injection. In the case of an arteriovenous fistula, the blood clot should stop the passage of blood from the artery to the vein. Surgery is usually used to correct acquired fistulas once they are diagnosed.

Resources

Books

Alexander, R. W., R. C. Schlant, and V. Fuster, eds. The Heart. 9th ed. New York: McGraw-Hill, 1998.
Berkow, Robert, ed. Merck Manual of Medical Information. Whitehouse Station, NJ: Merck Research Laboratories, 2004.
Braunwald, E. Heart Disease. Philadelphia: W. B. Saunders Co., 1997.

Key terms

Congenital — Present at the time of birth.

fistula

 [fis´tu-lah] (pl. fistulas, fis´tulae) (L.)
any abnormal tubelike passage within body tissue, usually between two internal organs or leading from an internal organ to the body surface. Some fistulas are created surgically for diagnostic or therapeutic purposes; others occur as result of injury or as congenital abnormalities. Among the many kinds of fistulas, the anal type (fistula in ano) is one of the most common. It generally develops as a result of a break or fissure in the wall of the anal canal or rectum, or an abscess there. Treatment is by surgery.

In women, difficult labor in childbirth may result in formation of a vesicovaginal fistula between the bladder and the vagina with resulting leakage of urine into the vagina. In a vesicointestinal fistula, there is leakage of urine from the bladder into the intestine. In a rectovaginal fistula, feces escape through the wall of the anal canal or rectum into the vagina. This condition, formerly a serious hazard of childbirth, is now rare; like other kinds of fistula, it can be corrected by surgery.

With the types of fistulas described here, typical symptoms are pain in the affected region and an abnormal discharge through the skin near the anus or through the vagina. Fistulas at different places of the body may be caused by tuberculosis, actinomycosis (a fungus infection), the presence of diverticula, or certain other serious diseases, and the fistula itself may be a site of infection and discomfort.
abdominal fistula one between a hollow abdominal organ and the surface of the abdomen.
anal fistula (fistula in a´no) one opening on the cutaneous surface near the anus, which may or may not communicate with the rectum.
arteriovenous fistula one between an artery and a vein, either pathologic (such as a varicose aneurysm) or surgically created to ensure an access site for hemodialysis. The site must be allowed 6 to 8 weeks to mature before it can be cannulated. Such a fistula may be the anastomosis of a natural artery and vein, a bovine graft, or a synthetic polytetrafluoroethylene (PTFE) graft. The bovine graft is taken from the bovine carotid artery and anastomosed to the vein and artery of the patient. In a PTFE graft, fibers are woven into a mesh called Gore-Tex and made into a sleeve and flange; this is available in a variety of sizes.

Precautions necessary to insure patient safety when caring for an individual with an arteriovenous fistula include frequent assessments for adequate circulation in the fistula and the distal extremity. A bruit or thrill can be heard over the access site. Blood pressure measurements, withdrawal of blood, injections, and administration of intravenous fluids should not be done on the extremity with such a fistula.
Internal arteriovenous fistulas.
blind fistula one open at one end only, opening on the skin (external blind fistula) or on an internal surface (internal blind fistula).
branchial fistula a persistent pharyngeal groove (branchial cleft).
Brescia-Cimino fistula an arteriovenous fistula for hemodialysis access, connecting the cephalic vein and radial artery.
bronchopleural fistula one between a bronchus and the pleural cavity, causing an air leak into the pleural cavity; sometimes seen as a complication of empyema, fibrosis, or pneumonia.
cerebrospinal fluid fistula one between the subarachnoid space and a body cavity, such as from head trauma or bone erosion, with leakage of cerebrospinal fluid, usually in the form of rhinorrhea or otorrhea.
complete fistula one extending from the skin to an internal body cavity.
craniosinus fistula one between the cerebral space and a paranasal sinus, permitting escape of cerebrospinal fluid into the nose.
Eck's fistula an artificial communication made between the portal vein and the vena cava.
enterocutaneous fistula see enterocutaneous fistula.
enterovesical fistula one connecting some part of the intestine with the urinary bladder; called also vesicoenteric f.
fecal fistula one between the colon and the external surface of the body, discharging feces.
gastric fistula
1. one communicating between the stomach and some other body part.
2. a passage created artificially through the abdominal wall into the stomach.
horseshoe fistula one near the anus, having a semicircular tract with both openings on the skin.
incomplete fistula blind fistula.
perilymph fistula rupture of the round window with leakage of perilymph into the inner ear, so that changes in middle ear pressure directly affect the inner ear, causing sensorineural deafness as well as dizziness, vertigo, nausea, and vomiting. Head trauma and dramatic changes in atmospheric pressure are the most common causes. The usual treatment is restriction in activity (sometimes with complete bed rest), so that the fistula can heal. Surgical repair may be necessary, consisting of placement of a graft over the defect.
pilonidal fistula pilonidal sinus.
pulmonary arteriovenous fistula a congenital fistula between the pulmonary arterial and venous systems, allowing unoxygenated blood to enter the systemic circulation.
rectovaginal fistula one between the rectum and vagina.
rectovesical fistula one between the rectum and urinary bladder.
salivary fistula one between a salivary duct or gland and the cutaneous surface, or into the mouth through an abnormal pathway.
thoracic fistula one communicating with the thoracic cavity.
umbilical fistula one communicating with the intestine or urachus at the umbilicus.
urinary fistula any fistula communicating between the urinary tract and another organ or the surface of the body.
vesicoenteric fistula (vesicointestinal fistula) enterovesical fistula.
vesicovaginal fistula one from the bladder to the vagina.

ar·te·ri·o·ve·nous fis·tu·la

an abnormal connection, either spontaneous or surgically created, between an artery and a vein.

arteriovenous fistula

an abnormal communication between an artery and vein. It may occur congenitally or result from trauma, infection, arterial aneurysm, or a malignancy. A continuous murmur and palpable thrill may be detected over the fistula and may be obliterated by compressing the feeding artery; this maneuver may slow the heartbeat (Branham's sign). Chronic arteriovenous fistulas may cause varicosities, cutaneous ulcers, and cardiac enlargement resulting from high-output heart failure. A congenital fistula may result in a cavernous hemangioma. If an arteriovenous fistula is limited in size and is accessible, it can be treated by surgical excision. An arteriovenous fistula is often created surgically to provide vascular access for hemodialysis.
enlarge picture
Arteriovenous fistula

arteriovenous fistula

Surgery
1. Arteriovenous shunt, see there.
2. A post-traumatic anastomosis between arteries and veins, which bypasses the capillary bed.

ar·te·ri·o·ve·nous fis·tu·la

(ahr-tēr'ē-ō-vē'nŭs fis'tyū-lă)
An abnormal communication between an artery and a vein, usually resulting in the formation of an arteriovenous aneurysm.

arteriovenous fistula

An abnormal communication between an artery and a vein. It may be congenital or the result of injury or disease. Blood is shunted at high pressure into the vein causing it to enlarge and become thickened and arterialized.

ar·te·ri·o·ve·nous fis·tu·la

(ahr-tēr'ē-ō-vē'nŭs fis'tyū-lă)
An abnormal communication between an artery and a vein, usually resulting in the formation of an arteriovenous aneurysm.

arteriovenous

both arterial and venous; pertaining to both artery and vein.

arteriovenous anastomosis
a direct connection between an artery and a vein that acts as a shunt to bypass the capillary bed. These occur in areas where a high volume blood supply is needed only intermittently, e.g. the intestine.
arteriovenous fistula
an abnormal communication between an artery and a vein; includes cardiac defects such as ventricular septal defects and patent ductus arteriosus. Peripheral fistulae, especially in the extremities, may be localized, usually acquired and the result of trauma, while congenital defects tend to be more diffuse, involving a network of anastomosing vessels.
The effects of arteriovenous fistulae are variable, depending on their location and the amount of blood carried. Within the liver they usually connect the hepatic artery and portal vein, causing portal hypertension and ascites. Small peripheral fistulae may be noticeable only as warm, reducible swellings, often with an audible thrill, or give rise to edema distal to the site. More severe effects are also possible.
pulmonary arteriovenous fistula
a congenital anomalous communication between the pulmonary arterial and venous systems, allowing unoxygenated blood to enter the systemic circulation.

Patient discussion about arteriovenous fistula

Q. I developed an AV Fistula after a heart catherization procedure. I am bleeding through the tissues in left arm I am on coumadin, but currently have a lower than usual INR. Corrective surgery was scheduled for yesterday, but had to be delayed. I am concerned that I have a large amount of blood (dark red) bleeding though the tissues right under the skin in my left arm. Should I seek immediate medical attention? The bleeding is over approximately a 3 and 1/2" area on my left arm. Came about in a period of a few minutes.

A. well, you are on blood thinners. i wouldn't take the chance. i mean- i'm not sure i follow what is happening over there. it could be a severe problem or nothing. i would let a doctor check it out. the worse thing that could happen is you wasting a day at the hospital, on the other end of that scenario- you can end up dead. i would go with the first one.

More discussions about arteriovenous fistula
References in periodicals archive ?
This case study reports the diagnosis and treatment of a carotid-cavernous sinus fistula that developed several months after a traumatic head injury.
Endovascular management of dural carotid-cavernous sinus fistulas in 141 patients.