An aneurysm is an abnormal bulge in the wall of an artery. Normally, the walls of arteries are thick and muscular, allowing them to withstand a large amount of pressure. Occasionally, however, a weak area develops in the wall of an artery. This allows the pressure within the artery to push outwards, creating a bulge or ballooned area called an "aneurysm."
Aneurysms can form in any blood vessel, but they occur most commonly in the aorta (aortic aneurysm). The aorta is the largest artery in the body. It carries blood from the heart to the rest of the body. Aortic aneurysms can occur in two main places:
Atherosclerosis -- hardening and narrowing of the arteries -- gets a lot of bad press but with good reason. This progressive process silently and slowly blocks arteries, putting blood flow at risk.
Atherosclerosis is the usual cause of heart attacks, strokes, and peripheral vascular disease -- what together are called "cardiovascular disease." Cardiovascular disease is the No. 1 killer in America, with more than 800,000 deaths in 2005.
How does atherosclerosis develop? Who gets it, and...
Congenital abnormality. A number of conditions, such as Marfan syndrome or bicuspid aortic valves are present at birth and can cause weakness of the artery walls.
Syphilis used to be a common cause of thoracic aneurysms, but it is no longer as common.
Note: Instead of causing a bulge in a thinned artery wall, aortic aneurysms occasionally occur between layers of the artery itself. This is called a "dissecting aneurysm." Blood starts to flow in the separated artery layers cutting off blood flow in the artery. This condition can rapidly lead to rupture of the artery.