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An aortic aneurysm is a weakened and bulging area in the aorta, the major blood vessel that feeds blood to the body. The aorta, about the thickness of a garden hose, runs through the center of your body. Because the aorta is the body's predominant supplier of blood, a ruptured aortic aneurysm can cause life-threatening bleeding. Although you may never have symptoms, finding out you have an aortic aneurysm can be more than unsettling. Each year, approximately 15,000 people die of an abdominal aortic aneurysm in the United States.

Most aneurysms are small and slow growing and rarely rupture. Less commonly, aneurysms are larger and faster growing and are at higher risk of rupturing. Depending on the size and rate at which it is growing, treatment for aortic aneurysm may vary from watchful waiting to emergency surgery. Once an aortic aneurysm is identified, doctors will closely monitor it so that surgery can be planned if and when necessary. Emergency surgery for a ruptured aneurysm carries increased risk and less chance of survival.

Aneurysms can develop anywhere along the aorta, but mostly occur in the abdominal section and are aptly called abdominal aortic aneurysms. Aneurysms that occur in the upper part of the aorta are called thoracic aortic aneurysms.

Aortic aneurysms often grow slowly and usually without symptoms, making them difficult to detect. Not all aortic aneurysms reach the point of rupture. Many start small and stay small, although many expand over time. Some aortic aneurysms enlarge slowly, increasing less than half an inch (1.2 centimeters) a year. Others expand at faster rates, which increases the risk of rupture. The rate at which aortic aneurysms may expand is difficult to predict.

As an aortic aneurysm enlarges, some people may notice:

• A pulsating sensation near the navel
• Tenderness or pain in the abdomen or chest
• Back pain

Although the exact cause of aneurysms is not certain, there are a number of factors strongly associated with their development.

Smoking is one of the most significant factors associated with the development of aortic aneurysms. In addition to the damaging effects of smoking directly to the arteries, smoking contributes to atherosclerosis, high blood pressure, and causes aneurysms to grow faster.

High blood pressure, especially if poorly controlled, increases the risk of developing an aortic aneurysm. Your sex, race and whether you've had a chest injury also have an impact on the chances of developing an aneurysm. In rare cases, aortic aneurysm may be caused by an infection or inflammation (vasculitis) that weakens a section of the aortic wall. There is often a pattern of aneurysm development among family members, suggesting a possible genetic component.

Some people are born with a weakness in the aortic wall that makes them more susceptible to aneurysm, particularly people with an inherited condition called Marfan syndrome, which affects the connective tissue in the body. Individuals with Marfan syndrome often have distinct physical characteristics, including tall stature, very long arms, a deformed breastbone and eye problems.

An aortic aneurysm is different from a condition known as aortic dissection, although aortic dissection often occurs in an area of the aorta affected by aneurysm. Artery walls consist of three layers — a thin inner layer, a muscular middle layer and a tough outer layer. In aortic dissection, a tear occurs in the aortic wall. This causes bleeding into and along the aortic wall and, in some cases, completely outside the aorta (rupture). Aortic dissection is a life-threatening emergency.

With age comes a decrease in the normal elasticity of your blood vessels. Abdominal aortic aneurysms are rare in people under the age of 60. This normal aging process coupled with other risk factors listed below may lead to an aortic aneurysm.

Factors that increase the risk of aortic aneurysm include:

• Smoking. Smoking is a strong risk factor for the development of an aortic aneurysm. The longer you've smoked, the greater your risk.
• High blood pressure. Increased blood pressure damages the blood vessels in the body, raising your chances of developing an aneurysm.
• Atherosclerosis. The buildup of fat and other substances damages the lining of a blood vessel, increasing the risk of the development of an aneurysm.
• Sex. Men develop aortic aneurysms five to 10 times more often than women do. However, women with aortic aneurysms have a risk of rupture significantly higher than do men.
• Race. Aortic aneurysms occur more commonly in whites than in people of other races.
• Family history. People who have a family history of aortic aneurysm are at increased risk (13 percent to 32 percent compared with the 2 percent to 5 percent risk in the general population) of having one themselves. People who have a family history of aneurysms tend to develop aneurysms at a younger age and are at higher risk of rupture.
• Marfan syndrome. The genetic condition Marfan syndrome affects the connective tissue throughout the body, including the tissues of the blood vessels. Having Marfan syndrome increases the risk of aortic aneurysm and dissection.

If you're at high risk, your doctor may recommend periodic screening with ultrasound examinations.

Most abdominal aortic aneurysms are found during an examination for another reason. For example, during a routine exam, your doctor may feel a pulsating bulge in your abdomen, though it's unlikely your doctor will be able to hear signs of an aneurysm through a stethoscope. Aortic aneurysms are often found during routine medical tests, such as a chest X-ray or ultrasound of the heart or abdomen, sometimes ordered for a different reason.

If your doctor suspects that you have an aortic aneurysm, specialized tests can confirm it. These tests might include an ultrasound, computerized tomography (CT) scan or magnetic resonance imaging (MRI) scan of your abdomen. These tests allow your doctor to get a detailed look at the organs and blood vessels in your chest and abdomen, including your aorta.

Because aortic aneurysms often don't cause symptoms, anyone who has risk factors for developing an aortic aneurysm should consider regular screening for the condition. In particular, guidelines recommend that men ages 65 to 75 who have ever smoked should have a one-time screening for abdominal aortic aneurysm using abdominal ultrasound. Men age 60 and older with a family history of abdominal aortic aneurysm should also consider screening.

Dissection or rupture of the aorta are the main complication of abdominal aortic aneurysm. Aortic dissection occurs when a tear in the inner lining of the aorta extends into the middle zone (media) of connective tissue. Rupture of the aorta occurs when the tear goes all the way through the aorta and into the chest or abdomen. A ruptured or dissecting aortic aneurysm results in life-threatening internal bleeding. In general, the larger the aneurysm, the greater the risk of rupture.

Signs and symptoms of a ruptured aortic aneurysm include:

• Sudden, intense and persistent abdominal, chest or back pain
• Pain that radiates to your back or legs
• Sweatiness
• Clamminess
• Dizziness
• Low blood pressure
• Fast pulse
• Loss of consciousness
• Shortness of breath

Another complication of aortic aneurysms is the risk of blood clots. Small blood clots can develop in the area of the aortic aneurysm. If a blood clot breaks loose from the inside wall of an aneurysm and blocks a blood vessel elsewhere in your body, it can cause pain or potentially life-threatening obstruction of blood flow to the legs, toes or abdominal organs. If the aneurysm is in the ascending aorta, blood clots or debris may break off and cause a stroke.

The goal of treatment is to prevent rupture of the aneurysm. Generally, your treatment options are to watch and wait or to have surgery. Your decision depends on the size of the aortic aneurysm and how fast it's growing. Here are the general guidelines for abdominal aortic aneurysms:

• Small aneurysm (4 cm or smaller). If you have a small aortic abdominal aneurysm — less than 2 inches, or about 4 centimeters (cm), in diameter — and you have no symptoms, your doctor may suggest a watch-and-wait (observation) approach, rather than surgery. If you choose this approach, your doctor will monitor your aneurysm with periodic ultrasounds, usually every six to 12 months and encourage you to report immediately if you start having abdominal tenderness or back pain — potential signs of a dissection or rupture. Your doctor may also recommend a high blood pressure medication called a beta blocker. Beta blockers decrease the force of blood ejection from the heart to minimize the expansion of the aneurysm. If you are a smoker, you should stop. Your doctor may recommend medications to lower cholesterol. If you have Marfan syndrome, your doctor may recommend an angiotensin receptor blocker, such as losartan, both to lower blood pressure and to try to stabilize the aorta. In general, surgery isn't needed for small aneurysms because the risk of surgery outweighs the risk of rupture.
• Medium aneurysm (between 4 cm and 5.5 cm). It's less clear how the risks of surgery versus waiting stack up in the case of a medium-size aortic abdominal aneurysm. If your aortic aneurysm is between 4 cm and 5.5 cm, you'll need to discuss the benefits and risks of waiting versus surgery and make a decision with your doctor.
• Large (5.5 cm or larger) or fast-growing aneurysm. If you have an aneurysm that is large or growing rapidly (more than 0.5 cm over six months), leaking, tender or painful, you'll probably need surgery. Surgery to repair an aortic aneurysm involves removing the damaged section of the aorta and replacing it with a synthetic tube (graft), which is sewn into place. This procedure requires open-abdominal or open-chest surgery involving a large incision in your chest and lengthy recover time.

A newer treatment for aortic aneurysm involves using a less invasive approach. Doctors attach a synthetic graft to the end of a thin tube (catheter) that's inserted through an artery in your leg and threaded up into your aorta. The graft — a woven tube covered by a metal mesh support — is deployed at the site of the aneurysm and fastened in place with small hooks or pins. The graft reinforces the weakened section of the aorta to prevent rupture of the aneurysm. This type of procedure is called endovascular surgery. Recover time is less than required for open-chest or abdominal surgery. Long-term results and benefits of endovascular surgery versus those of traditional surgery are unknown.

Although it's possible to repair a ruptured aortic aneurysm with emergency surgery, the risk is much higher and there is less chance of survival. Many people who experience a ruptured aortic aneurysm die before they reach the hospital.

Recommendations for surgical treatment of thoracic aortic aneurysms depend on the underlying condition, especially for people with Marfan syndrome, and location of the aneurysm.

There's no pill you can take to prevent an aortic aneurysm. Researchers are studying whether a class of antibiotics called tetracyclines can slow growth of small aortic aneurysms. It's too early to say whether these drugs will be effective. For people with Marfan syndrome, there is evidence from animal studies that the angiotensin receptor blocker losartan may prevent aneurysm formation.

For now the best approach to prevent an aortic aneurysm is to keep your blood vessels as healthy as possible. That means taking these steps:

• Keep your blood pressure under control.
• Don't smoke.
• Get regular exercise.
• Reduce cholesterol and fat in your diet.

Stopping smoking is particularly important because smoking increases the risk of aneurysm enlargement.

If you have some risk factors for aortic aneurysm, talk to your doctor. If you are at risk, your doctor may recommend additional measures, including medications to lower your blood pressure and relieve stress on weakened arteries. You may also want to consider regular screening ultrasounds.