Arteriovenous fistula

Arteriovenous fistula
Illustration of an arteriovenous fistula
Classification and external resources
Specialty	cardiology
ICD-10	I28.0, I77.0
ICD-9-CM	414.19, 417.0, 447.0, 747.3
DiseasesDB	32435
eMedicine	med/169
MeSH	D001164

This article is about AV fistulas in general. For the surgical procedure, see Cimino fistula.

"Arteriovenous shunt" redirects here. For nonpathologic AV shunts, see metarteriole and glomus body.

An arteriovenous fistula is an abnormal connection or passageway between an artery and a vein. It may be congenital, surgically created for hemodialysis treatments, or acquired due to pathologic process, such as trauma or erosion of an arterial aneurysm.

Causes

Congenital (developmental defect)
Rupture of arterial aneurysm into an adjacent vein
Penetrating injuries
Inflammatory necrosis of adjacent vessels
Intentionally created (for example, Cimino fistula as vascular access for hemodialysis)

Associated conditions

Hereditary hemorrhagic telangiectasia

Mechanism

When an arteriovenous fistula is formed involving a major artery like the abdominal aorta, it can lead to a large decrease in peripheral resistance. This lowered peripheral resistance causes the heart to increase cardiac output to maintain proper blood flow to all tissues. The physical manifestations of this would be a relatively normal systolic blood pressure with a decreased diastolic blood pressure resulting in a wide pulse pressure.

Normal blood flow in the brachial artery is 85 to 110 milliliters per minute (mL/min). After the creation of a fistula, the blood flow increases to 400–500 mL/min immediately, and 700–1,000 mL/min within 1 month. A bracheocephalic fistula above the elbow has a greater flow rate than a radiocephalic fistula at the wrist. Both the artery and the vein dilate and elongate in response to the greater blood flow and shear stress, but the vein dilates more and becomes "arterialized". In one study, the cephalic vein increased from 2.3 mm to 6.3 mm diameter after 2 months. When the vein is large enough to allow cannulation, the fistula is defined as "mature".^[1]

An arteriovenous fistula can increase preload.^[2] AV shunts also decrease the afterload of the heart. This is because the blood bypasses the arterioles which results in a decrease in the total peripheral resistance (TPR). AV shunts increase both the rate and volume of blood returning to the heart.

Complications

Just like berry aneurysm, an intracerebral arteriovenous fistula can rupture causing subarachnoid hemorrhage.^[3]

References

↑ Vascular, Vol. 14, Supl. 1, Nov. 2006, p. S1
↑ "Pulmonary: Heart Failure". Archived from the original on 1 February 2009. Retrieved 2008-12-21.
↑ Park, Myung K. (2002). Pediatric cardiology for practitioners. With a contribution by R. George Troxler (4th ed.). St. Louis: Mosby. ISBN 0-323-01444-5.

External links

Arteriovenous Fistula at Merck Manual
Overview at Mayo Clinic

Cardiovascular disease (vessels) (I70–I99, 440–456)

Arteries, arterioles
and capillaries

Inflammation

Peripheral artery disease

Arteriosclerosis	Atherosclerosis Foam cell Fatty streak Atheroma Intermittent claudication Critical limb ischemia Monckeberg's arteriosclerosis Arteriolosclerosis Hyaline Hyperplastic Cholesterol LDL Oxycholesterol Trans fat

Stenosis	Carotid artery stenosis Renal artery stenosis

Other	Aortoiliac occlusive disease Degos disease Erythromelalgia Fibromuscular dysplasia Raynaud's phenomenon

Aneurysm / dissection /
pseudoaneurysm

Vascular malformation

Vascular nevus

Veins

Inflammation	Phlebitis

Venous thrombosis / Thrombophlebitis	primarily lower limb Deep vein thrombosis abdomen Hepatic veno-occlusive disease Budd–Chiari syndrome May–Thurner syndrome Portal vein thrombosis Renal vein thrombosis upper limb / torso Mondor's disease Paget–Schroetter disease head Cerebral venous sinus thrombosis Post-thrombotic syndrome

Varicose veins	Gastric varices Portacaval anastomosis Caput medusae Esophageal varices Hemorrhoid Varicocele

Other	Chronic venous insufficiency Chronic cerebrospinal venous insufficiency Superior vena cava syndrome Inferior vena cava syndrome Venous ulcer

Arteries or veins

Blood pressure

Hypertension	Hypertensive heart disease Hypertensive emergency Hypertensive nephropathy Essential hypertension Secondary hypertension Renovascular hypertension Benign hypertension Pulmonary hypertension Systolic hypertension White coat hypertension

Hypotension	Orthostatic hypotension

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