Aortic aneurysm

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An aortic aneurysm is a general term for any localized dilatation or aneurysm of the aorta, usually representing an underlying weakness in the wall of the aorta at that location. This physical change in the aortic diameter can occur secondary to an intrinsic defect in the protein construction of the aortic wall, trauma, infection, or due to progressive destruction of aortic proteins by enzymes. The last is the most common cause of aneurysmal disease although the origin of this enzymatic destruction is not known.

Most intact aortic aneurysms do not produce any symptoms and frequently cannot be detected by a physician's physical examination without imaging tests. Untreated, aneurysms tend to become progressively larger, although the rate of enlargement is unpredictable for any individual. The risk to an individual's health, however, results primarily from the potential of an aortic aneurysm to rupture, causing massive internal hemorrhage, usually resulting in a quick death. Rarely, clotted blood which lines most aortic aneurysms can break off and result in an embolus.

Aortic aneurysms commonly occur in the abdominal aorta, as abdominal aortic aneurysms (AAA), where the walls are thinner. Some AAAs may swell to over 6 inches in diameter before rupturing. An abdominal aortic aneurysm can often be palpated by firm pressure above and around the navel as a large, pulsatile mass.

Aortic aneurysms less commonly form in the thoracic aorta, where they are known as thoracic aortic aneurysms. In about half of the individuals with a thoracic aortic aneurysm, an underlying cause is Marfan syndrome. Most of the rest of the individuals with thoracic aortic aneurysms have hypertension. Syphilis is a rare cause of ascending aortic aneurysms.

Treatment

Medical therapy of aortic aneurysms involves strict blood pressure control. This does not treat the aortic aneurysm per se, but tight blood pressure control with prevention of hypertension may decrease the rate of expansion of the aneurysm.

The definitive treatment for an aortic aneurysm is surgical repair of the aorta. This typically involves opening up of the dilated portion of the aorta and insertion of a dacron patch tube. Once the tube is sewn into the proximal and distal portions of the aorta, the aneurysmal sac is closed around the artificial tube.

A recent treatment option is the placement of a stent via a percutaneous technique into the diseased portion of the aorta. Percutaneous stenting of aortic aneurysms has a lower mortality rate than an open surgical approach, and has been used in individuals with co-morbid conditions that make them a high risk for surgery.

The determination of when surgery should be performed is usually based on the diameter of the aneurysm. A rapidly expanding aneurysm should be operated on as soon as feasible, since it has a greater chance of rupture. Slowly expanding aortic aneurysms may be followed by routine diagnostic testing (ie: CT scan or ultrasound imaging). If the aortic aneurysm grows at a rate of more than 1 cm/year, surgical treatment should be electively performed.

The current treatment guidelines suggest elective surgical repair of an abdominal aortic aneurysm when the diameter of the aneurysm is greater than 5cm. However, recent data suggests medical management for abdominal aneurysms with a diameter of less than 5.5 cm.1

In the case of thoracic aortic aneurysms, the current recommendation for treatment of an ascending aortic aneurysm is elective repair when the diameter is greater than 5.5 cm if the individual does not suffer from Marfan syndrome. If the aneurysm is below the arch of the aorta, the treatment of a descending thoracic aortic aneurysm is elective repair when the diameter is greater than 6.5 cm. In individuals with Marfan syndrome, surgical treatment of an ascending aneurysm should be performed when the diameter of the aorta reaches 5cm, while treatment of a descending thoracic aneurysm should be performed when the diameter of the aorta reaches 6 cm.

See also

References

1. Mortality results for randomised controlled trial of early elective surgery or ultrasonographic surveillance for small abdominal aortic aneurysms. The UK Small Aneurysm Trial Participants. Lancet. 1998 Nov 21;352(9141):1649-55. (Medline abstract (http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=pubmed&dopt=Abstract&list_uids=9853436))

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