Enlargement of a section of the aorta due to weakness in the artery wall
If a section of an artery wall becomes weakened, the pressure of blood in the artery may cause it to bulge out. The bulging section of the artery is called an aneurysm. An aneurysm may occur in any artery in the body, but the aorta, the major artery that transports blood away from the heart, is most commonly involved. Three-quarters of all aortic aneurysms occur in the abdominal section of the aorta below the kidneys, and this type of aneurysm tends to run in families. Aortic aneurysms may also develop in the chest. The risk of having an aneurysm increases with age, and the condition most commonly occurs in men over the age of 65.
Small aortic aneurysms do not usually produce symptoms, although large ones may cause localized pain. In some enlarged aneurysms, known as dissecting aneurysms, the inner layer of the arterial wall tears and peels away from the outer layer, allowing blood to collect in the space between the two. The larger an aneurysm is, the more likely it is to rupture, causing internal bleeding that can rapidly prove fatal.
The cause of most aneurysms is uncertain, but they are often associated with atherosclerosis, in which fatty deposits build up in the artery walls. The risk of developing atherosclerosis is increased by some lifestyle factors, such as smoking, eating a diet high in fat, excess weight, and taking little exercise. Aneurysms are also more common in males and people with high blood pressure (see Hypertension).
In rare cases, an injury or an inherited weakness in the artery wall leads to the development of an aneurysm. For example, the genetic disorder Marfan’s syndrome may lead to the formation of multiple aneurysms.
Symptoms vary according to the site and usually develop when an aneurysm enlarges. The symptoms of an abdominal aneurysm may include:
Pain in the abdomen that may spread to the back and can be relieved temporarily by leaning forwards.
Pulsating sensation in the abdomen.
An aneurysm in the chest may produce symptoms such as:
Pain in the chest or in the upper back between the shoulder blades.
Severe cough and wheezing.
Difficulty swallowing and hoarseness.
If you have symptoms of this kind, you should seek emergency medical help.
Sometimes, a blood clot forms at the site of the aneurysm and may obstruct the passage of blood through the aorta. In the case of a dissecting aneurysm, the torn part of the artery wall may block arteries that branch from the aorta close to the aneurysm. In the abdomen, such blockages may result in a reduced blood supply to the intestines or kidneys. If the obstruction occurs in the chest, branches of the aorta leading to the neck or the arms may be affected.
Pressure in the aorta may eventually cause an aneurysm to rupture, allowing blood to leak from the vessel and causing worsening pain. If rupture occurs suddenly, you may have severe pain accompanied by loss of consciousness, a fast pulse, and shock. Without immediate medical treatment, a ruptured aneurysm is likely to be fatal.
If there are no symptoms, an aneurysm may be detected during a routine physical examination when a doctor feels a swelling in the abdomen. Sometimes, an aneurysm is seen on an X-ray of the chest or abdomen carried out to check for another disorder. Screening tests for abdominal aortic aneurysm may be advised for some men over the age of 65. Ultrasound scanning may be carried out at intervals to measure the diameter of the aorta and see if the aneurysm is enlarging. CT scanning, MRI, or, rarely, angiography (see Contrast X-rays), may also be performed to image the affected arteries.
An aneurysm may be treated by surgery, the aim of which is to repair the artery before the aneurysm dissects or ruptures. Your doctor will consider your age and general state of health, as well as the size and site of the aneurysm, when deciding whether surgery is necessary. Surgery for larger aneurysms involves removing the weakened area of arterial wall and replacing it with a graft of synthetic material. To prevent complications from developing while you are waiting for surgery, you may be given beta-blockers or other antihypertensive drugs to lower blood pressure in the artery. For a dissecting or ruptured aneurysm, you may need to have emergency surgery. In some cases, an aneurysm may be treated by implanting a large stent (tube) covered with an impermeable lining across the aneurysm, a procedure called a TVAR (transvascular aortic repair). The stent is inserted via a small incision in the femoral artery (the main artery in the leg) and passed up inside the artery to the area of the aneurysm, where it is fixed in place.
If you are a smoker, you should give up immediately and completely. For anyone who has had an aneurysm, a low-fat diet (see A healthy diet) and regular exercise will help to slow the progress of atherosclerosis and thus reduce the risk of further aneurysms.
Surgery on an aneurysm offers a good chance of recovery provided the aneurysm has not yet dissected or ruptured. If the aneurysm has dissected or ruptured, between 15 and 50 per cent of people survive, depending on the location of the blood vessel affected.
From the 2010 revision of the Complete Home Medical Guide © Dorling Kindersley Limited.