An aortic aneurysm is enlargement (dilation) of the aorta to greater than double the normal size. They usually cause no symptoms except when ruptured. Occasionally there may be abdominal, back or leg pain.
They are most commonly located in the abdominal aorta, but can also be located in the thoracic aorta (Chest). Aortic aneurysms cause weakness in the wall of the aorta and increase the risk of aortic rupture. When rupture occurs, massive internal bleeding results, and, unless treated immediately, shock and death can occur. The other fatal complication that can occur is dissection of the aorta. The layers of the wall of the aorta split due to the weakening caused by the aneurysm. This can result in mal-perfusion to the brain or visceral organs or eventual rupture. In both the situations emergency intervention is warranted. Both, rupture and dissection, have high mortality despite prompt medical treatment. Hence it is recommended to intervene electively, depending on size of aneurysm, before these complications occur.
Types of Aneurysms
Aortic aneurysms are classified by their location on the aorta.
- Thoracic aortic aneurysms
- Abdominal aortic aneurysms, “AAA” or “Triple A,”
Which are found within the chest; these are further classified as ascending, aortic arch, or descending aneurysms.
The most common form of aortic aneurysm, involve the segment of the aorta within the abdominal cavity. Thoraco-abdominal aortic aneurysms involve both the thoracic and abdominal aorta.
Signs and symptoms
Most intact aortic aneurysms do not produce symptoms. As they enlarge, symptoms such as abdominal pain and back pain may develop. Compression of nerve roots may cause leg pain or numbness. Untreated, aneurysms tend to become progressively larger, although the rate of enlargement is unpredictable for any individual.
Aneurysms can be found on physical examination. Medical imaging is necessary to confirm the diagnosis and to determine the anatomic extent of the aneurysm.
Abdominal aortic aneurysms
Abdominal aortic aneurysms (AAAs) are more common than thoracic. The prevalence of AAAs increases with age, with an average age of 65–70 at the time of diagnosis. AAAs have been attributed to atherosclerosis, though other factors are involved in their formation.
The risk of rupture of an AAA is related to its diameter; once the aneurysm reaches about 5 cm, the yearly risk of rupture may exceed the risks of surgical repair for an average-risk patient. Rupture risk is also related to shape; so-called “fusiform” (long) aneurysms are considered less rupture prone than “saccular” (shorter, bulbous) aneurysms, the latter having more wall tension in a particular location in the aneurysm wall.
The diagnosis of an abdominal aortic aneurysm can be confirmed at the bedside by the use of ultrasound. Rupture may be indicated by the presence of free fluid in the abdomen. A contrast-enhanced abdominal CT scan is the best test to diagnose an AAA and guide treatment options.
Only 10–25% of patients survive rupture due to large pre- and post-operative mortality. Annual mortality from ruptured aneurysms in the United States is about 15,000. Most are due to abdominal aneurysms, with thoracic and thoracoabdominal aneurysms making up 1% to 4% of the total.
Etiology
An aortic aneurysm can occur as a result of trauma, infection, or, most commonly, from an intrinsic abnormality in the elastin and collagen components of the aortic wall. Definite genetic abnormalities were identified in true genetic syndromes (Marfan, Elher-Danlos and others) associated with aortic aneurysms. Other risk factors include: Hypertension, Hypercholesterolemia, Tobacco use and Bicuspid Aortic Valve. The progressive enlargement of an aneurysm can be prevented by controlling patient’s blood pressure, smoking and cholesterol levels.
Treatment
Surgery (open or endovascular) is the definite treatment of an aortic aneurysm. Medical therapy is typically reserved for smaller aneurysms or for elderly, frail patients where the risks of surgical repair exceed the risks of non-operative therapy (observation alone).
Medical therapy of aortic aneurysms involves strict blood pressure control. This does not treat the aortic aneurysm per se, but control of hypertension within tight blood pressure parameters may decrease the rate of expansion of the aneurysm.
The medical management of patients with aortic aneurysms, reserved for smaller aneurysms or frail patients, involves cessation of smoking, blood pressure control, use of statins and occasionally beta blockers. Ultrasound studies are obtained on a regular basis (i.e. every six or 12 months) to follow the size of the aneurysm.