Atherosclerosis

What is atherosclerosis?

Atherosclerosis, or "hardening of the arteries," occurs when certain substances build up in the artery wall. These substances include cholesterol, minerals, blood, and muscle cells. This buildup makes the artery stiffer than normal and causes partial or complete blockage of blood flow.

Atherosclerosis affects mainly the medium-sized arteries, such as the coronary arteries, carotid and cerebral (brain) arteries, and kidney arteries. It is also commonly found in the largest artery in the body, the aorta, and its branches to the arms and legs. Atherosclerosis tends to collect near branching points in the arteries.

Atherosclerosis is more common as people get older and gets worse over time. It is the leading cause of death and disability in the US.

How does it occur?

Atherosclerosis is a sequence of events. The first event is an injury of some kind - no one knows exactly what - that damages the filmy layer of cells called the endothelium that lines the artery. The injury may be due to the stress of blood flow in the vessel. Other causes might be virus damage, irritants such as nicotine or drug stimulants, or an allergic reaction.

At the point of injury, circulating white blood cells called monocytes attach themselves to the vessel wall and burrow beneath the surface. The monocytes change into cells called macrophages that start to gobble up small particles of fatty substances called lipids. Lipids, which include fats and cholesterol, are carried all over the body by the blood. The macrophages gobble up so much that they burst, causing more injury and repeating the cycle.

Platelets, another component of blood, also recognize the injury and attach themselves to the injured area. The platelets secrete a chemical that stimulates the growth of more smooth muscle cells in the wall of the artery. This repair attempt thickens and stiffens the artery wall. An important side effect of this muscle cell activity is to increase the amount of fibrous, or connective, tissue in the injured area. The entire thickened area is called a plaque.

If the plaque remained stable, all would probably be well. However, the disease generally worsens and usually takes one of two forms: slow plaque growth or plaque rupture.

Some plaques grow very slowly and gradually cause the artery to become more narrow. In time, this narrowing may block the artery enough to reduce the blood flow through it. When that happens, heart muscle tissue beyond the narrowing begins to suffer from lack of oxygen.

Rupture, or breaking open, of the plaque surface is a serious problem. No one knows what causes it. When rupture occurs, bad things may happen quickly. The rupture releases potent enzymes and other irritating substances. This causes a clot to form at the rupture. The clot may get large enough to partially or completely block the flow of blood through the artery. A heart attack, stroke, or kidney failure can result. Even if the rupture and clot are small, there may be repeated ruptures of the same plaque until the clot is large enough to cause constant symptoms or symptoms that come and go.

What are the symptoms?

The process can go on unnoticed for many years until lack of blood flow to a part of the body causes symptoms, which can include problems such as:

pain in the calf muscles with exercise (intermittent claudication)
pain in the chest (angina)
a mini-stroke (transient ischemic attack) or dizziness.

How is it diagnosed?

The diagnosis is confirmed by special x-rays to outline the arteries (angiography), by ultrasound (sonogram), or by pulse-tracing techniques.

How is it treated?

Your health care provider may prescribe treatment for conditions related to the atherosclerosis. Depending on your symptoms, he or she may give you medicine to reduce blood clotting or to relax the blood vessels. You may need surgery.

Your provider may advise major lifestyle changes to try to halt or reverse the buildup of plaque in your arteries. You may be advised to:

Stop smoking.
Lose weight.
Start an exercise program.
Practice stress reduction.
Switch to a low-fat, low-cholesterol diet.

How can I take care of myself?

Take the medication prescribed and follow your health care provider's advice for lifestyle changes.
Have your blood pressure and blood cholesterol checked regularly.
If you smoke, quit. Tell your provider if you need help quitting.
If you are overweight, talk to your provider about losing weight.
Exercise regularly under the guidance of your provider.
Switch to a low-fat, low-cholesterol, high-fiber diet. Your provider or a dietician can tell you which foods to avoid.
If it's okay with your provider, take an aspirin a day. However, check with your provider first. There may be reasons why you shouldn't.

Can atherosclerosis be prevented?

Because the cause of atherosclerosis is unknown, it cannot be prevented.