Atherosclerosis

Atherosclerosis is a disease characterized by the deposition of fatty substances called plaques in the walls of medium and large arteries. Depending on which arteries are affected, it can lead to leg pain, erectile dysfunction, cardiovascular disease and heart attack, or stroke. It is the main cause of death in developed countries.

The disease often starts in childhood and the arteries become clogged over many years, initially without symptoms.

Mechanism of the disease

High blood pressure, cholesterol, smoking, diabetes, sedentary life style[?], hormone status and age are all risk factors for athersclerosis. These factors conspire to cause tears to the lining of the medium and large arteries[?], which results in fatty deposits[?], inflammation, and ultimately narrowing of the afflicted arteries. High blood pressure provides the shear force to produce tears in the fragile endothelium[?], the lining of the arteries. Cholesterol migrates into these torn sections when concentrations of LDL, or low density lipoprotein are high. Smoking has a direct toxic effect on the arterial wall, causing an inflammatory response. Exercise modifies many of these risk factors, ultimately lowering the inflammatory response of the arterial walls. Hormones, especially the presence of estrogen, has a healing effect on the arterial walls. 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. This can lead to narrowing (stenosis[?]) of the artery. The atheromas are fragile. When they rupture, a partial blockage can be quickly converted into a complete obstruction, resulting in a heart attack or stroke, depending on which artery is obstructed.

Risk factors

These risk factors for atherosclerosis are known:

• having high blood concentration of LDL ("bad cholesterol") or of triglycerides and low concentration of HDL ("good cholesterol"). HDL particles transport cholesterol from the tissues back to the liver.
• 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
• tobacco smoking
• having trouble managing stress
• being obese
• being physically inactive
• some chemicals indicating ongoing inflammation may also point to high risk

High-risk patients are given a low-fat diet, exercise and cholesterol-lowering drugs.

Treatment

If 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.

High blood pressure, diabetes, or high blood cholesterol can be treated as well. Lowering the 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.

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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