Health A-Z

Medical Content Created by the Faculty of the
Harvard Medical School

Atherosclerosis

What Is It?

Atherosclerosis is a narrowing of the arteries that can significantly reduce the blood supply to vital organs such as the heart, brain and intestines. In atherosclerosis, the arteries are narrowed when fatty deposits called plaques build up inside. Plaques typically contain cholesterol from low-density lipoproteins (LDL), smooth-muscle cells and fibrous tissue, and sometimes calcium.

As a plaque grows along the lining of an artery, it produces a rough area in the artery's normally smooth surface. This rough area can cause a blood clot to form inside the artery, which can totally block blood flow. As a result, the organ supplied by the blocked artery starves for blood and oxygen. The organ's cells may either die or suffer severe damage.

Atherosclerosis is the main cause of death and disability in industrialized nations, including the United States. This is because atherosclerosis is the underlying medical problem in most patients with any of the following illnesses:

• Coronary artery disease — In this chronic (long-lasting) disease, atherosclerosis narrows the coronary arteries, the arteries that supply blood to the heart muscle. This can lead to the chest pain called angina. It also increases the risk of a heart attack, which occurs when a coronary artery is blocked completely.

• Stroke — A blood clot (thrombus) may form inside a brain artery that has been narrowed by atherosclerosis. Once this thrombus forms, it cuts off the blood supply to part of the brain, causing a thrombotic stroke. Currently, about 75% of strokes in industrialized countries are thrombotic strokes.

• Abdominal angina and bowel infarction — When atherosclerosis narrows arteries that supply blood to the intestines, it causes a form of abdominal pain called abdominal angina. Complete, sudden blockage of intestinal blood supply can cause a bowel infarction. A bowel infarction is similar to a heart attack, but it involves the intestines rather than the heart.

• Atherosclerosis of the extremities — Atherosclerosis can narrow the major arteries that supply blood to the legs, especially the femoral and popliteal arteries. These two arteries are affected in 80% to 90% of people with this problem. The reduced blood flow to the legs may result in a crampy leg pain during exercise called intermittent claudication. If blood flow is compromised severely, parts of the leg may become pale or cyanotic (turn blue), feel cold to the touch and eventually develop gangrene.

• Other conditions — Atherosclerosis may be a factor in the development of an aortic aneurysm or renal artery stenosis (narrowing of the kidney arteries).

Factors that increase your risk of developing atherosclerosis include:

• High level of blood cholesterol (hypercholesterolemia)

• Low level of HDL (the "good cholesterol")

• High levels of C-reactive protein, a marker for inflammation

• High blood pressure (hypertension)

• Diabetes

• Family history of coronary artery disease at an early age

• Cigarette smoking

• Obesity

• Physical inactivity (too little regular exercise)

• Older age