What are Aortic Aneurysms?

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The aorta runs from the heart, through the chest and abdomen to supply all the major organs of the body. An aneurysm is a dilatation or swelling of an artery. In this case, there is an abdominal aortic aneurysm (also known as an AAA or "Triple-A") and a left iliac artery aneurysm. Images courtesy of Medtronic.

The aorta is the main artery that carries blood from the heart to most other organs of the body. When it becomes enlarged or swollen it is called an aortic aneurysm. This usually develops over a very long period of time and is difficult to notice or feel because it is so deep inside the body. Despite the fact that it is so well protected it can still cause serious problems. These include:

  1. Thrombosis: This is when the aneurysm blocks off completely and the flow of blood stops. This can lead to a shortage of blood to organs such as muscles in the legs or buttocks causing pain when walking or running (claudication), or sometimes such severe lack of blood that there is a risk of gangrene. This is extremely rare in aortic aneurysms but can happen in other aneurysms such as those of the popliteal artery behind the knee.
     
  2. Embolism: This is when clot that has formed inside the aneurysm can break up and shoot further down the aorta and into a branch vessel. This can include the arms or legs, or other organs such as the kidneys, spleen, liver or gut. Again this is very rare from an aortic aneurysm.
     
  3. Compression: As the aneurysm gets larger it can compress nearby structures. In the chest or abdomen most nearby structures will move out of the way and it is extremely unusual for an aneurysm to cause any problems purely because of its size.
     
  4. Rupture: This is the most concerning risk of aortic aneurysms of the abdomen or thorax. The risk is greater the larger the aneurysm and rises dramatically after the aneurysm enlarges beyond a critical size. Beyond this cutoff size it is generally recommended that the aneurysm is repaired to prevent rupture. It is not known exactly what causes aneurysms, but some theories suggest that inflammation related to atherosclerosis, or cholesterol damage to the arteries, can weaken the wall of the artery. This may be worsened or associated with longstanding high blood pressure or a genetic tendency to develop aneurysms or have weak elastic tissues. There are no proven methods to prevent an aneurysm from developing.

Here is a link to a brief video about Aortic Aneurysms.

We do not truly understand why aortic aneurysms develop in some people and not others. Factors known to be associated with aortic aneurysms include:

  • Advanced age
  • Male gender
  • Smoking
  • High blood pressure
  • High cholesterol
  • Aneurysms elsewhere in the body
  • A family history of aneurysms
  • Some connective tissue diseases and inherited syndromes

American guidelines currently suggest that males over 65 with a history of smoking should be screened for an abdominal aortic aneurysm with ultrasound (USPSTF Report, 2005).