aneurysm

aneurysm , localized dilatation of a blood vessel, particularly an artery , or the heart . Dilatation of an artery, and therefore weakness of that portion of the arterial wall, may be rarely congenital, or it may be caused by syphilis , hypertension (high blood pressure), arteriosclerosis , bacterial and fungal infections, or penetrating injury as from a bullet or knife. An aneurysm may be asymptomatic or it may cause varying symptoms, depending upon its location and size and on whether the expanding mass is pressing on adjacent nerves or vital organs. The weakened arterial walls of an aneurysm are always in danger of sudden rupture, with resulting hemorrhage and death.

Aneurysms occur most commonly in the large arteries; the aorta , the largest vessel in the body, is the one most often affected. Ventricular aneurysms of the heart often occur after myocardial infarctions . Aneurysms also occur in the arteries within the skull and in other areas of the body.

Aneurysms can be detected by echocardiogram, spin echo magnetic resonance imaging scans, coronary arteriograms, and biplane ventriculograms. Treatment, where feasible, may involve surgery to remove the aneurysm or the insertion of coiled wire to close it off. Coiled wire can only be used on aneurysms that are connected to the blood vessel by a narrowed neck. The coiling fills the aneurysm, obstructing the flow of blood into the dilatation, and blood clots form around the wire, preventing the aneurysm from bursting. Surgical excision of the dilated saclike portion of the affected artery sometimes requires the replacement of that portion by a synthetic graft, a section of vessel (made of polymer fiber) that is similar in size.

aneurysm (an-yoor-izm) n. an abnormal balloon-like swelling in the wall of an artery, due to disease or congenital deficiency. aortic a. an aneurysm that most frequently occurs in the abdominal aorta, below the level of the renal arteries (abdominal aortic a., AAA). Beyond a certain size it is prone to rupture: an acute surgical emergency. arteriovenous a. a direct communication between an artery and vein, without an intervening capillary bed. berry a. a small saccular aneurysm commonly affecting branches of the circle of Willis in the brain. Usually associated with congenital weakness of the vessels, they are a cause of cerebral haemorrhage in young adults. Charcot-Bouchard a. a small aneurysm found within the brain of elderly and hypertensive subjects. Such aneurysms may rupture, causing cerebral haemorrhage. dissecting a. a condition in which a tear occurs in the lining of (usually) the first part of the aorta, which allows blood to enter the wall and track along (dissect) the muscular coat. A dissecting aneurysm may rupture or it may compress the blood vessels arising from the aorta and produce infarction (localized necrosis) in the organs they supply. ventricular a. a condition that may develop in the wall of the left ventricle after myocardial infarction. Heart failure may result or thrombosis within the aneurysm may act as a source of embolism.
—aneurysmal adj.

aneurysm Local dilatation (swelling and weakening) of the wall of a blood vessel, usually the result of atherosclerosis and hypertension; especially serious when occurring in the aorta, when rupture may prove fatal.