Arteriovenous aneurysm Health Dictionary

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Arteriovenous Aneurysm: From 1 Different Sources

a direct communication between an artery and vein, without an intervening capillary bed. It can occur as a congenital abnormality or it may be acquired following injury or surgery. It may affect the limbs, lungs, or viscera and may be single or multiple. If the connection is large, the short-circuiting of blood may produce heart failure. Large isolated arteriovenous aneurysms may be closed surgically.
Health Source: Oxford | Concise Colour Medical Dictionary
Author: Jonathan Law, Elizabeth Martin

Aneurysm

A localised swelling or dilatation of an artery (see ARTERIES) due to weakening of its wall. The most common sites are the AORTA, the arteries of the legs, the carotids and the subclavian arteries. The aorta is the largest artery in the body and an aneurysm may develop anywhere in it. A dissecting aneurysm usually occurs in the ?rst part of the aorta: it is the result of degeneration in the vessel’s muscular coat leading to a tear in the lining; blood then enters the wall and tracks along (dissects) the muscular coat. The aneurysm may rupture or compress the blood vessels originating from the aorta: the outcome is an INFARCTION in the organs supplied by the affected vessel(s). Aneurysms may also form in the arteries at the base of the brain, usually due to an inherited defect of the arterial wall.

Aneurysms generally arise in the elderly, with men affected more commonly than women. The most common cause is degenerative atheromatous disease, but other rarer causes include trauma, inherited conditions such as MARFAN’S SYNDROME, or acquired conditions such as SYPHILIS or POLYARTERITIS NODOSA. Once formed, the pressure of the circulating blood within the aneurysm causes it to increase in size. At ?rst, there may be no symptoms or signs, but as the aneurysm enlarges it becomes detectable as a swelling which pulsates with each heartbeat. It may also cause pain due to pressure on local nerves or bones. Rupture of the aneurysm may occur at any time, but is much more likely when the aneurysm is large. Rupture is usually a surgical emergency, because the bleeding is arterial and therefore considerable amounts of blood may be lost very rapidly, leading to collapse, shock and even death. Rupture of an aneurysm in the circle of Willis causes subarachnoid haemorrhage, a life-threatening event. Rupture of an aneurysm in the abdominal aorta is also life-threatening.

Treatment Treatment is usually surgical. Once an aneurysm has formed, the tendency is for it to enlarge progressively regardless of any medical therapy. The surgery is often demanding and is therefore usually undertaken only when the aneurysm is large and the risk of rupture is therefore increased. The patient’s general ?tness for surgery is also an important consideration. The surgery usually involves either bypassing or replacing the affected part of the artery using a conduit made either of vein or of a man-made ?bre which has been woven or knitted into a tube. Routine X-ray scanning of the abdominal aorta is a valuable preventive procedure, enabling ‘cold’ surgery to be performed on identi?ed aneurysms.... aneurysm

Berry Aneurysm

An abnormal swelling that occurs at the junction of arteries supplying the brain. Berry aneurysms, which are usually due to a congenital weakness, can sometimes rupture, resulting in a subarachnoid haemorrhage.

(See also aneurysm.)... berry aneurysm

Arterio-venous Aneurysm

An abnormal communication between an artery and a vein. It is usually the result of an injury, such as a stab or a gunshot wound, which involves both a neighbouring artery and vein.... arterio-venous aneurysm

Cirsoid Aneurysm

The condition in which a group of arteries become abnormally dilated and tortuous.... cirsoid aneurysm

Arteriovenous Fistula

An abnormal communication directly between an artery and a vein. An arteriovenous fistula may be present at birth or result from injury. A fistula can also be created surgically for easy access to the bloodstream in dialysis.... arteriovenous fistula

Aortic Aneurysm

see aneurysm.... aortic aneurysm

Arteriovenous Anastomosis

a thick-walled blood vessel that connects an arteriole directly with a venule, thus bypassing the capillaries. Arteriovenous anastomoses are commonly found in the skin of the lips, nose, ears, hands and feet; their muscular walls can constrict to reduce blood flow or dilate to allow blood through to these areas.... arteriovenous anastomosis

Arteriovenous Malformation

see angioma.... arteriovenous malformation

Endovascular Aneurysm Repair

(EVAR) a recently developed technique that involves the insertion of a covered metal *stent into an *aneurysm. The stent lines the aneurysm and thereby excludes it from the circulation, preventing further expansion and rupture. The delivery system containing the stents is introduced through the common femoral artery. *Fluoroscopy provides real-time imaging to guide placement of the stents and ensure they are in the correct anatomical position.... endovascular aneurysm repair

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