An aneurysm describes an abnormal and excessive stretching in the wall of a blood vessel. Aneurysms can occur in any type of blood vessel, including arteries and veins, but most often occur in an artery--a blood vessel that carries oxygenated blood away from the heart to the body. Many different conditions and diseases can cause the wall of the artery to become weak, allowing the pressure of the blood against the walls to create a bulge, resulting in an aneurysm.
Types of Aneurysms
The National Heart Lung and Blood Institute report that most aneurysms occur in the aorta--the main artery that carries oxygenated blood to the body. Doctors classify an aneurysm that affects the portion of the aorta in the chest cavity as a thoracic aortic aneurysm. Abdominal aortic aneurysms occur in the portion of the aorta in the abdominal cavity. Approximately 75 percent of all aortic aneurysms occur in the abdominal cavity, according to the Mayo Clinic. Other types of aneurysms include brain aneurysms and peripheral aneurysms that affect any artery other than the aorta or those in the brain.
Medical Conditions
Blood pressure describes the force the blood exerts against the walls of the blood vessels. High blood pressure, defined by the American Heart Association as a reading of 140 mm Hg over 90 mm Hg, can damage artery walls and lead to an aneurysm. High blood pressure also contributes to atherosclerosis, a condition in which fatty substances build up on the artery walls, causing them to become weak.
Infections, such as syphilis that remains untreated or endocarditis--an infection causing inflammation of the inner layer of the heart, can also lead to an aneurysm. Vasculitis, a condition characterized by inflammation of the blood vessels, occurs when the immune system mistakenly attacks blood vessels. This also can weaken the vessel walls and lead to an aneurysm.
Genetic Conditions
Several types of genetic conditions can lead to thoracic aortic aneurysms. Marfan syndrome describes a disorder that affects the connective tissue found in ligaments, tendons, blood vessel walls, cartilage and heart valves. Marfan syndrome weakens the walls of the aorta, leading to an aneurysm or a dissection--a tear in the artery wall--as described by the American Heart Association. Other genetic disorders that can contribute to the formation of aneurysms include Loeys-Dietz syndrome, which is similar to Marfan syndrome, and Ehlers-Danlos syndrome, which also affects connective tissues.
Injuries
Trauma, such as might occur in a car accident, that causes injury to the chest or abdominal region can weaken the aorta and lead to an aneurysm. Other traumatic events, such as falls from significant heights, can also cause damage leading to an aneurysm.
Outlook
An aneurysm, especially a small aneurysm, usually goes undetected. A large aneurysm, however, can rupture or burst, causing internal bleeding that requires prompt medical attention. A brain aneurysm can lead to a stroke, a condition in which cells in the brain become damaged or die. As of April 2009, approximately 14,000 Americans die annually due to aneurysms, according to the National Heart Lung and Blood Institute.
