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Abdominal Aortic Aneurysms
An abdominal aortic aneurysm (AAA) is a bulge in the segment of the aorta (the main blood vessel exiting the heart which supplies blood to all body organs) located in the abdomen. Aneurysms may occur in any blood vessel, but the most common occur in the abdominal aorta, typically below the level of the renal arteries (the vessels that provide blood to your kidneys). An aneurysm may continue to grow larger until, bulging like a balloon, it ruptures. The larger an aneurysm grows, the higher the likelihood that it will rupture. Aneurysm rupture can be a life-threatening event. Thus, the goal of aneurysm repair surgery is the prevention of aortic rupture.
The normal, healthy aorta below the renal arteries typically measures about 2.3 cm in diameter (1 inch) in men and 1.9 cm in diameter (3/4 inch) in women, but often varies with age and body size. An aorta is typically considered aneurysmal when it grows to more than 50% of its normal, healthy size. The presence of aneurysms is four times more common in men than women, and occurs most frequently in people over the age of 55-60 years old.
According to the American Heart Association (AHA) and American College of Cardiology (ACC), aneurysm rupture is the 13th leading cause of death in the US, affecting approximately 15,000 people per year. The incidence of aortic aneurysm disease increases every 10 years as the population ages in general. Early detection and diagnosis is increasingly possible as more sophisticated medical screening methods become available.
Symptoms of Aneurysmal Disease
Three out of four aneurysms show no symptoms at the time they are diagnosed. Those patients who do have symptoms may feel a pulsation in their abdomen or an occasional mild abdominal ache, back pain or groin pain. Most people have few complaints related to the presence of an aneurysm.
However, rapid growth or rupture of an abdominal aortic aneurysm may cause intense back or abdominal pain, and signs of hemodynamic shock such as; shaking, dizziness, fainting, sweating, rapid heartbeat, and sudden weakness. When this happens, seek immediate medical attention.
Causes and Risk Factors for Aneurysmal Disease
Aneurysms are caused by a weakening of, or damage to, the wall of a blood vessel. Risks factors that have been associated with the presence of aneurysmal disease include:
- Cigarette smoking
- Coronary artery disease
- High blood pressure
- Inflammation or Infection
There is a strong positive correlation between cigarette smoking and the presence of aneurysms. Smokers are up to four times more likely to die from ruptured aneurysms than nonsmokers. Aneurysms in smokers have been shown to both expand and weaken faster than in nonsmokers. Coronary artery disease is also highly associated with the presence of abdominal aortic aneurysms. Coronary artery disease occurs when substances such as cholesterol, minerals, and blood cells build up in the walls of the artery, damaging the elastic properties of the vessel wall. The muscular wall of the vessel, particularly the aorta, weakens and later begins to characteristically bulge. High blood pressure may further accelerate the weakening process, but it is not a cause or aneurysmal disease on its own. Aneurysms have been shown to run in familial lines, so there is some evidence of a hereditary role in the develop of aneurysmal disease.
Diagnosis of Aneurysms
Aneurysms are most often found during a routine physical exam or when a doctor examines your heart, gallbladder or kidneys. An abdominal aortic aneurysm can be felt as a pulsating mass within the abdominal area. Once discovered, the aneurysm's size is determined, as the risk of aneurysm rupture has been shown to correlate with size.
In current clinical practice, aneurysms less than 4.5 cm in diameter are not typically considered to require immediate surgical repair, but are indicated for on-going surveillance by a physician. Those between 4.5 and 5 cm should be carefully watched with more frequent intervals, as they may require surgery if they demonstrate a propensity to grow in size over time. Aneurysms larger than 5 cm may be indicated for surgical repair, depending on the condition of the patient and other clinical factors.
Some of the diagnostic test modalities that can be used to help diagnose and evaluate the presence of aneurysms include:
- Ultrasound - which uses sound waves emitted across the abdominal cavity to create a virtual image of the aorta and its surrounding structures. An abdominal ultrasound examination is a non-invasive, easy and accurate way to measure the size of an aneurysm.
- CT (computerized tomography) - scan, which uses x-rays and contrast media to visualize the vascular system. Abdominal CT scans can be used to determine the size of the enlarging aorta.
- MRI (magnetic resonance imaging) - which uses a combination of radio waves and a magnetic field to show your visualize the vascular system.
- Arteriogram - which uses x-rays and contrast media to visualize blood flow through the vascular system.