Misplaced Pages

Revision as of 12:07, 25 November 2002

Atherosclerosis is a disease characterized by the deposition of fatty substances in the walls of medium and large arteries. It can lead to stroke and heart attack and is the main cause of death in developed countries.

Cholesterol, an important component of cell membranes, travels in the blood from the liver and intestines to the tissues in the form of low density lipoprotein (LDL) particles. If the LDL concentration is too high, these particles can accumulate in the artery walls (intima) where the fat oxidizes. The resident cells interpret this as an intrusion, "call for help", and inflammation results. Immune cells called monocytes circulating in the blood enter the artery wall, turn into macrophages and ingest the LDL particles, thereby turning into large "foam cells". The inflammation also causes a fibrous cap to be formed between the fatty deposits and the artery. These capped fatty deposits (called atheromas) narrow the blood vessel. In some cases, this can lead to complete blockage (stenosis) of the artery; more commonly, the caps eventually break and a blood clot forms at the rupture. In both cases, essential blood flow can be interrupted and heart attack or stroke can result.

To assess the risk of an individual, one typically measures the ratio of LDL to HDL concentration in the blood (HDL particles transports cholesterol from the tissues back to the liver). Some chemicals indicating ongoing inflammation may also point to high risk. High-risk patients are given a low-fat diet, exercise and fat-lowering drugs.

What is atherosclerosis?

Atherosclerosis is the buildup of fatty deposits called plaque on the inside walls of arteries. Arteries are blood vessels that carry oxygen and blood to the heart, brain, and other parts of the body. As plaque builds up in an artery, the artery gradually narrows and can become clogged. As an artery becomes more and more narrowed, less blood can flow through. The artery may also become less elastic (called "hardening of the arteries"). Atherosclerosis is the main cause of a group of diseases called cardiovascular diseases - diseases of the heart and blood vessels.

Atherosclerosis can lead to clogged arteries in any part of the body. When the arteries to the heart are affected, angina (chest pain) or a heart attack may result. If arteries in the leg are affected, leg pain may occur. Atherosclerosis of the arteries to the brain can cause strokes.

Atherosclerosis is common in the United States. It often starts in childhood and the arteries become narrowed or clogged over many years.

What is plaque?

Plaque is a combination of cholesterol, other fatty materials, calcium, and blood components that stick to the artery wall lining. A hard shell or scar covers the plaque. Plaques have various sizes and shapes. Some plaques are unstable and can rupture or burst. When this happens, it causes blood clotting inside the artery. If a blood clot totally blocks the artery, it stops blood flow completely. This is what happens in most heart attacks and strokes. What causes plaque to form in arteries?

Although many risk factors are well known, the exact causes of atherosclerosis are not clear. Too much cholesterol in the blood, damage to the artery wall, and inflammation appear to play important roles in plaque buildup. Researchers are studying why and how the arteries become damaged, how plaque develops and changes over time, and why plaque can break open and lead to blood clots. There may be other factors that prove to be important in causing atherosclerosis. What are the symptoms of atherosclerosis?

There are usually no symptoms until one or more arteries are so clogged with plaque that blood flow is severely reduced. This reduced flow of blood and oxygen to some part of the body (such as the heart) is called ischemia and may cause pain or discomfort. Some people have no symptoms until a blood clot forms, completely blocks an already narrowed artery, and causes a heart attack or stroke.

The symptoms you have depend on which arteries are badly clogged and what part of the body is affected by the reduced flow of blood.

• If arteries taking blood to your heart muscle are affected, you have coronary artery disease (CAD). You may have chest pain called angina that happens when you exert yourself and goes away when you rest. You could also have a heart attack.
• If arteries taking blood to your brain are affected, you have cerebrovascular disease. You could have a transient ischemic attack (TIA) or a stroke.
• If arteries taking blood to your legs are affected, you have peripheral arterial disease (PAD). You may have pain in the calf or thigh muscle called intermittent claudication that happens when you walk. This kind of pain goes away when you stop and rest.

All of these conditions are serious and should not be ignored. Arteries taking blood to the intestines, the kidneys, or other organs can also become clogged by plaque. This can sometimes lead to a medical emergency similar to a heart attack or stroke. Atherosclerosis can also cause erectile dysfunction in men. What risk factors raise my chances of having atherosclerosis?

These risk factors raise your chances of having atherosclerosis:

• having high blood cholesterol, especially high LDL ("bad cholesterol") and low HDL ("good cholesterol") levels
• aging and being male (women are affected more after menopause)
• having close relatives who had heart disease or a stroke at a relatively young age
• having high blood pressure
• having diabetes
• smoking
• having trouble managing stress
• being obese
• being physically inactive

The more risk factors you have, the more likely it is that you have atherosclerosis. Talk with your health care provider about your risks for atherosclerosis and cardiovascular disease.

How is atherosclerosis diagnosed?

If you don't have any symptoms and have not been diagnosed with cardiovascular disease, it is not easy to tell if your arteries are becoming clogged with plaque. But if you have high blood cholesterol, are overweight and get little exercise, smoke, or have other risk factors, there is a good chance that you have atherosclerosis. Eventually it can lead to heart disease, a stroke or other problems.

There are a number of tests that doctors use in diagnosing cardiovascular diseases, including blood tests, electrocardiograms (ECG), stress testing, coronary angiography, ultrasound, and computed tomography (CT). If you are at high risk for cardiovascular disease, your health care provider may suggest that you be tested.

Researchers are studying new tools to help find cardiovascular disease in earlier stages, before symptoms appear. For example, the National Heart, Lung, and Blood Institute is sponsoring a ten-year study called the Multi-Ethnic Study of Atherosclerosis (MESA). The MESA study will help show which risk factors are the best predictors of future heart disease in men and women and in certain ethnic groups.

How is atherosclerosis treated?

If your atherosclerosis leads to symptoms, the symptoms (such as angina) can be treated. Medicines are usually the first step in treating cardiovascular diseases. Other treatments include angioplasty procedures to open up clogged arteries and surgery, such as bypass surgery.

If you have high blood pressure, diabetes, or high blood cholesterol, these conditions can be treated as well. Lowering your blood cholesterol level can slow, stop, or even reverse the buildup of plaque. Cholesterol lowering can reduce the cholesterol content in unstable plaques to make them more stable and less prone to rupture.

One of the most important ways to have healthier arteries is to make lifestyle changes. Adopt a healthy diet, balance healthful eating with regular physical activity, don't smoke, and lose weight if you are overweight. If you have high blood cholesterol, high blood pressure or diabetes, follow your treatment plan. Making lifestyle changes can also help control these health problems.

Some of the text on this page has been taken from the public domain document at http://www.4woman.gov/faq/atheroscle.htm

References:

• Peter Libby: Atherosclerosis: The New View, Scientific American Vol 286, No. 5, May 2002
• Merck Manual: Atherosclerosis, http://www.merck.com/pubs/mmanual/section16/chapter201/201b.htm