aneurysm, aneurism

(an′yŭ-rizm )

[Gr. aneurysma, a widening]
Localized abnormal dilatation of a blood vessel, usually an artery, due to a congenital defect or weakness in the wall of the vessel. As aneurysms dilate, they become more and more vulnerable to rupture.
aneurysmal (an″yŭ-riz′măl), adj.

As people age, the combined effects of high blood pressure and atherosclerotic weakening of arteries produce most aneurysms in the aorta. Congenital malformations of arteries in the circle of Willis are relatively common causes of aneurysms in the brain. Aneurysms in the chest or peripheral arteries are sometimes caused by blunt trauma or by bacterial or mycotic infection.

abdominal aortic aneurysm

ABBR: AAA A localized dilatation (saccular, fusiform, or dissecting) of the wall of the abdominal aorta. It is generally found to involve the renal arteries and frequently the iliac arteries. Occasionally the dilatation can extend upward through the diaphragm to the thoracic aorta.

The incidence and prevalence of AAA increases sharply with advancing age. Slightly more than 1% of men between the ages of 45 and 54 have AAA. Approx. 12% of men over the age of 75 have AAA.

Symptoms, when present, include generalized abdominal pain, low back pain unaffected by movement, and sensations of gastric or abdominal fullness. Sudden severe lumbar or abdominal pain radiating to the flank and groin, esp. if associated with tachycardia and hypotension, may indicate enlargement or imminent rupture. Signs can include a pulsating mass in the periumbilical area and a systolic bruit over the aorta.

Current screening guidelines recommend that all hypertensive male smokers over the age of 65 undergo a screening ultrasound of the abdominal aorta. Because most people with an abdominal aortic aneurysm are asymptomatic, before routine screening was employed, most AAAs were detected incidentally, e.g., during abdominal examinations or abdominal x-rays taken for other reasons.

The enlargement of an AAA can be prevented with careful control of blood pressure and atherosclerotic risk factors. Patients who smoke tobacco products need to stop smoking. Hyperlipidemia and elevated blood glucose levels should be professionally managed. Once an AAA is identified, serial imaging studies should be performed (usually every few years) to gauge whether the aneurysm has enlarged to a diameter at which surgical intervention is indicated. Small, asymptomatic aneurysms may be followed over time, rather than repaired (see below). CT, MRI, or aortography may assist in confirming the diagnosis and the condition of proximal and distal vessels.

Untreated abdominal aortic aneurysms gradually enlarge and in some instances rupture. The likelihood of rupture increases for aneurysms that are larger than 5.5 cm. Surgical repair is recommended for all aneurysms larger than 6 cm. If an aneurysm is tender and known to be enlarging rapidly (no matter what its size), surgery is strongly recommended. Surgical therapy consists of replacing the aneurysmal segment with a synthetic fabric (Dacron) graft. Immediate surgery is indicated for a ruptured aortic abdominal aneurysm. An alternative treatment to traditional laparotomy is to insert a bypass graft percutaneously into the aorta.

In acute dissection of an abdominal aortic aneurysm, oxygenation, blood pressure, and cardiac rhythm are closely monitored, and a pulmonary artery line may be inserted to monitor hemodynamics. The patient is observed for signs of aneurysmal rupture, which may be fatal. He or she will require an intravenous line via a large-bore catheter, a urinary catheter, and an arterial line and pulmonary artery catheter to monitor fluid and hemodynamic balance. Additionally, cardiac monitor electrodesare placed, and a nasogastric tube inserted.

Prescribed medications are administered to manage contributory factors such as hypertension and hypercholesterolemia; a beta-adrenergic blocking agent may be prescribed to reduce the risk of expansion and rupture. The patient is instructed in their use and taught how adverse effects should be reported. In acute aortic rupture, admission to the ICU is arranged, a blood sample is obtained for typing and cross-matching, and a large-bore (14G) venous catheter is inserted to facilitate blood replacement. The patient is prepared for and informed about elective surgery, if indicated, or emergency surgery if rupture occurs. The patient will require an intravenous line via a large-bore catheter, a urinary catheter, and an arterial line and pulmonary artery catheter to monitor fluid and hemodynamic balance. Additionally, cardiac monitor electrodes are placed, and a nasogastric tube inserted. During surgery the patient will be intubated and mechanically ventilated; such therapies will most likely still be in place postoperatively in the ICU.

Desired outcomes include the patient's ability to express anxiety, use support systems, and perform stress-reduction techniques that assist with coping; to demonstrate abatement of physical signs of anxiety; to avoid activities that increase the risk of rupture; to understand and cooperate with the prescribed treatment regimen; to identify indications of rupture and to institute emergency measures; to maintain normal fluid and blood volume in acute situations; and to recover from elective or emergency surgery with no complications. Post-operative patients are usually assisted to ambulate by the second day after surgery. Pain management and psychological support are extremely important during the acute postoperative period.

aortic aneurysm

An aneurysm affecting any part of the aorta from the aortic valve to the iliac arteries. The dilated artery is usually asymptomatic and is detected as an incidental finding during imaging.

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arteriovenous aneurysm

An aneurysm of congenital or traumatic origin in which an artery and vein become connected. Symptoms may include pain, expansive pulsation, and bruits or, occasionally, high-output heart failure.

atherosclerotic aneurysm

Aneurysm due to degeneration or weakening of the arterial wall caused by atherosclerosis.

Bérard aneurysm

SEE: Bérard aneurysm

berry aneurysm

A small saccular congenital aneurysm of a cerebral vessel. It communicates with the vessel through a small opening. Rupture of this type of aneurysm may cause subarachnoid hemorrhage, a devastating form of stroke.

cerebral aneurysm

Aneurysm of a blood vessel in the brain.

Charcot-Bouchard aneurysm

SEE: Charcot-Bouchard aneurysm

cirsoid aneurysm

A dilatation of a network of vessels commonly occurring on the scalp. The mass may form a pulsating subcutaneous tumor.
SYN: SEE: racemose aneurysm

compound aneurysm

Aneurysm in which some of the layers of the vessel are ruptured and others dilated.

dissecting aneurysm

Aneurysm in which the blood makes its way between the layers of a blood vessel wall, separating them; a result of necrosis of the medial portion of the arterial wall.
SEE: aortic aneurysm for illus.

fusiform aneurysm

Aneurysm in which all the walls of a blood vessel dilate more or less equally, creating a tubular swelling.
SEE: aortic aneurysm for illus.

mycotic aneurysm

Aneurysm caused bybacterial infection.

racemose aneurysm

SEE: Cirsoid aneurysm

sacculated aneurysm

Aneurysm in which there is weakness on one side of the vessel; usually due to trauma. It is attached to the artery by a narrow neck.
SEE: aortic aneurysm for illus.

varicose aneurysm

Aneurysm forming a blood-filled sac between an artery and a vein.

venous aneurysm

Localized expansion and weakening of the wall of a vein.