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Aortic Aneurysm

Aortic Aneurysm Definition and Overview

Abnormal enlargement or bulging of the aorta, the largest blood vessel of the body, is not an unusual condition. Medical professionals refer to this as aneurysm of the great vessel, or aortic aneurysm. The enlargement usually affects only a small part of the vessel, so bulge is a more accurate description.

An aneurysm occurs when a segment of the vessel becomes weakened. The pressure of the blood flowing through the vessel creates a bulge at the weak spot, much as an overinflated inner tube can cause a bulge in a tire. The bulge usually starts small and grows as the pressure continues. Aneurysms are dangerous because they can rupture, causing internal bleeding.

The aorta is an artery, meaning it carries oxygen-rich blood from the heart. It is the main artery coming from the heart.

  • It extends from the left chamber (ventricle) of the heart and goes through the chest, down through the belly, or midsection of the body (abdomen), and into the pelvis (groin).
  • In the groin, it divides into two vessels that supply blood to the lower trunk and both legs.
  • In the chest, the aorta is called the thoracic aorta; in the abdomen, the abdominal aorta.

Almost every artery in the body branches off of the aorta. These arteries supply blood to the brain, other vital organs (liver, stomach, small and large bowel, spinal cord) and nerves, bones, muscles, and cells that allow the body to function.

  • Damage to the aorta can threaten vital functions.
  • If the damage is severe enough, or not treated, it can even cause death.

Bulging can occur in any artery in the body. It is most common in the arteries of the brain and in the abdominal aorta.

  • In the aorta, bulging can occur anywhere along the entire vessel.
  • It is most common in the abdominal aorta, where it is known as abdominal aortic aneurysm (triple AAA).
  • If it occurs in the thoracic aorta, it is known as thoracic aortic aneurysm.

Arteries are muscular tubes. The wall of the artery is made up of three layers: the innermost layer (the intima), the middle layer (the media), and the outer layer (the adventitia). Bulges in an artery are classified as true aneurysm, false aneurysm, or dissection.

  • A true aneurysm involves all three layers of the blood vessel wall.
  • A false aneurysm of the artery is contained only by the two outer layers of the blood vessel wall and clot. This is a very fragile condition with high risk of bursting. False aneurysms are usually a result of an infection.

A related but different condition is aortic dissection. Dissection refers to a separation of the vessel wall, which allows blood to leak between the layers of the vessel. This further damages and weakens the vessel, placing it at much greater risk of bursting (rupture).

Because the abdominal aorta is such a large vessel, a ruptured abdominal aneurysm is a life-threatening event.

  • Fortunately, not all aneurysms rupture right away. Many grow very slowly and cause no symptoms or problems for many years.
  • When detected in time, most aneurysms can be electively repaired with an operation so they do not rupture.

Each year, about 15,000 people in the United States die of a ruptured abdominal aneurysm. This makes it the 13th leading cause of death in this country.

  • Most aneurysms occur in people aged 55 years or older.
  • The number of aneurysms in the United States is increasing as the population increases and ages.
  • Aneurysms are four times more common in men than in women.
Medically Reviewed by a Doctor on 1/8/2013
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Abdominal Aortic Aneurysm »

Abdominal aortic aneurysms (AAAs) represent a degenerative process of the abdominal aorta that is often attributed to atherosclerosis; however, the exact cause is not known. A familiar clustering of AAAs has been noted in 15-25% of patients undergoing repair of the problem.

Read More on Medscape Reference »


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