What Is an Aneurysm?

An aneurysm (AN-u-rism) is an abnormal bulge or “ballooning” in the wall of an artery. Arteries are blood vessels that carry oxygen-rich blood from the heart to other parts of the body. An aneurysm that grows and becomes large enough can burst, causing dangerous, often fatal, bleeding inside the body.

Most aneurysms occur in the aorta. The aorta is the main artery that carries blood from the heart to the rest of the body. The aorta comes out from the left ventricle (VEN-trih-kul) of the heart and travels through the chest and abdomen. An aneurysm that occurs in the aorta in the chest is called a thoracic (tho-RAS-ik) aortic aneurysm. An aneurysm that occurs in the aorta in the abdomen is called an abdominal aortic aneurysm.

Aneurysms also can occur in arteries in the brain, heart, intestine, neck, spleen, back of the knees and thighs, and in other parts of the body. If an aneurysm in the brain bursts, it causes a stroke.

About 15,000 Americans die each year from ruptured aortic aneurysms. Ruptured aortic aneurysm is the 10th leading cause of death in men over age 50 in the United States.

Many cases of ruptured aneurysm can be prevented with early diagnosis and medical treatment. Because aneurysms can develop and become large before causing any symptoms, it is important to look for them in people who are at the highest risk. Experts recommend that men who are 65 to 75 years old and have ever smoked (at least 100 cigarettes in their lifetime) should be checked for abdominal aortic aneurysms.

When found in time, aneurysms can usually be treated successfully with medicines or surgery. If an aortic aneurysm is found, the doctor may prescribe medicine to reduce the heart rate and blood pressure. This can reduce the risk of rupture.

Large aortic aneurysms, if found in time, can often be repaired with surgery to replace the diseased portion of the aorta. The outlook is usually excellent.

What Causes an Aneurysm?

An aneurysm can result from atherosclerosis (hardening and narrowing of the inside of arteries). As atherosclerosis develops, the artery walls become thick and damaged and lose their normal inner lining. This damaged area of artery can stretch or “balloon” from the pressure of blood flow inside the artery, resulting in an aneurysm.

An aneurysm also can develop from constant high blood pressure inside an artery.

A thoracic aortic aneurysm can result from an injury to the chest (for example, an injury that occurs from an auto crash). Certain medical conditions, such as Marfan syndrome, that weaken the body’s connective tissues, also can cause aneurysms.

In rare cases, infections such as untreated syphilis (a sexually transmitted infection) can cause aortic aneurysms. Aortic aneurysms also can occur as a result of diseases that cause inflammation of blood vessels, such as vasculitis.

Types of Aneurysm

Types of aneurysm include aortic aneurysms, cerebral aneurysms, and peripheral aneurysms.
Aortic Aneurysm

Most aneurysms occur in the aorta. The aorta is the main artery that carries blood from the heart to the rest of the body. The aorta comes out from the left ventricle of the heart and travels through the chest and abdomen. The two types of aortic aneurysm are thoracic aortic aneurysm (TAA) and abdominal aortic aneurysm (AAA).
Thoracic Aortic Aneurysm

An aortic aneurysm that occurs in the part of the aorta running through the thorax (chest) is a thoracic aortic aneurysm. One in four aortic aneurysms is a TAA.

Most TAAs do not produce symptoms, even when they are large. Only half of all people with TAAs notice any symptoms. TAAs are identified more often now than in the past because of chest computed tomography (CT) scans performed for other medical problems.

In a common type of TAA, the walls of the aorta become weak and a section nearest to the heart enlarges. Then the valve between the heart and the aorta cannot close properly and blood leaks backward into the heart. Less commonly, a TAA can develop in the upper back away from the heart. A TAA in this location can result from and injury to the chest such as from an auto crash.
Abdominal Aortic Aneurysm

An aortic aneurysm that occurs in the part of the aorta running through the abdomen is an abdominal aortic aneurysm. Three in four aortic aneurysms are AAAs.

An AAA can grow very large without producing symptoms. About 1 in 5 AAAs rupture.

Cerebral Aneurysm

Aneurysms that occur in an artery in the brain are called cerebral aneurysms. They are sometimes called berry aneurysms because they are often the size of a small berry. Most cerebral aneurysms produce no symptoms until they become large, begin to leak blood, or rupture.

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EditText of this page (last edited February 12, 2008)