Tuesday, December 2, 2008

What Is Atherosclerosis?

Atherosclerosis (ath-er-o-skler-O-sis) is a disease in which plaque (plak) builds up on the insides of your arteries. Arteries are blood vessels that carry oxygen-rich blood to your heart and other parts of your body.

Plaque is made up of fat, cholesterol, calcium, and other substances found in the blood. Over time, plaque hardens and narrows your arteries. The flow of oxygen-rich blood to your organs and other parts of your body is reduced. This can lead to serious problems, including heart attack, stroke, or even death.

Figure A shows a normal artery with normal blood flow. Figure B shows an artery with plaque buildup.

Atherosclerosis can affect any artery in the body, including arteries in the heart, brain, arms, legs, and pelvis. As a result, different diseases may develop based on which arteries are affected.

Coronary artery disease (CAD). This is when plaque builds up in the coronary arteries. These arteries supply oxygen-rich blood to your heart. When blood flow to your heart is reduced or blocked, it can lead to chest pain and heart attack. CAD also is called heart disease, and it's the leading cause of death in the United States.
Carotid (ka-ROT-id) artery disease. This happens when plaque builds up in the carotid arteries. These arteries supply oxygen-rich blood to your brain. When blood flow to your brain is reduced or blocked, it can lead to stroke.
Peripheral arterial disease (PAD). This occurs when plaque builds up in the major arteries that supply oxygen-rich blood to the legs, arms, and pelvis. When blood flow to these parts of your body is reduced or blocked, it can lead to numbness, pain, and sometimes dangerous infections.
Some people with atherosclerosis have no signs or symptoms. They may not be diagnosed until after a heart attack or stroke.

The main treatment for atherosclerosis is lifestyle changes. You also may need medicines and medical procedures. These, along with ongoing medical care, can help you live a healthier life.

The cause of atherosclerosis isn’t known. However, certain conditions may raise your chances of developing it. These conditions are known as risk factors. You can control some risk factors, such as lack of physical activity, smoking, and unhealthy eating. Others you can’t control, such as age and family history of heart disease.

Better treatments have reduced the number of deaths from atherosclerosis-related diseases. These treatments also have improved the quality of life for people with these diseases. Still, the number of people diagnosed with atherosclerosis remains high.

You may be able to prevent or delay atherosclerosis and the diseases it can cause, mainly by maintaining a healthy lifestyle. This, along with ongoing medical care, can help you avoid the problems of atherosclerosis and live a long, healthy life.

Other Names for Atherosclerosis
Arteriosclerosis (ar-TER-e-o-skler-o-sis)
Hardening of the arteries

What Causes Atherosclerosis?
The exact cause of atherosclerosis isn't known. However, studies show that atherosclerosis is a slow, complex disease that may start in childhood. It develops faster as you age.

Atherosclerosis may start when certain factors damage the inner layers of the arteries. These factors include:

High amounts of certain fats and cholesterol in the blood
High blood pressure
High amounts of sugar in the blood due to insulin resistance or diabetes
When damage occurs, your body starts a healing process. Fatty tissues release compounds that promote this process. This healing causes plaque to build up where the arteries are damaged.

Over time, the plaque may crack. Blood cells called platelets (PLATE-lets) clump together to form blood clots where the cracks are. This narrows the arteries more and worsens angina (chest pain) or causes a heart attack.

Researchers continue to look at why atherosclerosis develops. They hope to find answers to such questions as:

Why and how do the arteries become damaged?
How does plaque develop and change over time?
Why does plaque break open and lead to clots?

Who Is At Risk for Atherosclerosis?
Coronary artery disease (atherosclerosis of the coronary arteries) is the leading cause of death in the United States.

The exact cause of atherosclerosis isn't known. However, certain traits, conditions, or habits may raise your chance of developing it. These conditions are known as risk factors. Your chances of developing atherosclerosis increase with the number of risk factors you have.

You can control most risk factors and help prevent or delay atherosclerosis. Other risk factors can't be controlled.

Major Risk Factors
Unhealthy blood cholesterol levels. This includes high LDL cholesterol (sometimes called bad cholesterol) and low HDL cholesterol (sometimes called good cholesterol).
High blood pressure. Blood pressure is considered high if it stays at or above 140/90 mmHg over a period of time.
Smoking. This can damage and tighten blood vessels, raise cholesterol levels, and raise blood pressure. Smoking also doesn't allow enough oxygen to reach the body's tissues.
Insulin resistance. This condition occurs when the body can't use its own insulin properly. Insulin is a hormone that helps move blood sugar into cells where it's used.
Diabetes. This is a disease in which the body’s blood sugar level is high because the body doesn’t make enough insulin or doesn’t use its insulin properly.
Overweight or obesity. Overweight is having extra body weight from muscle, bone, fat, and/or water. Obesity is having a high amount of extra body fat.
Lack of physical activity. Lack of activity can worsen other risk factors for atherosclerosis.
Age. As you get older, your risk for atherosclerosis increases. Genetic or lifestyle factors cause plaque to build in your arteries as you age. By the time you're middle-aged or older, enough plaque has built up to cause signs or symptoms.
In men, the risk increases after age 45.
In women, the risk increases after age 55.
Family history of early heart disease. Your risk for atherosclerosis increases if your father or a brother was diagnosed with heart disease before 55 years of age, or if your mother or a sister was diagnosed with heart disease before 65 years of age.
Although age and a family history of early heart disease are risk factors, it doesn't mean that you will develop atherosclerosis if you have one or both.

Making lifestyle changes and/or taking medicines to treat other risk factors can often lessen genetic influences and prevent atherosclerosis from developing, even in older adults.

Emerging Risk Factors
Scientists continue to study other possible risk factors for atherosclerosis.

High levels of a protein called C-reactive protein (CRP) in the blood may raise the risk for atherosclerosis and heart attack. High levels of CRP are proof of inflammation in the body. Inflammation is the body's response to injury or infection. Damage to the arteries' inner walls seems to trigger inflammation and help plaque grow.

People with low CRP levels may get atherosclerosis at a slower rate than people with high CRP levels. Research is under way to find out whether reducing inflammation and lowering CRP levels also can reduce the risk of atherosclerosis.

High levels of fats called triglycerides in the blood also may raise the risk of atherosclerosis, particularly in women.

Other Factors That Affect Atherosclerosis
Other risk factors also may raise your risk for developing atherosclerosis. These include:

Sleep apnea. Sleep apnea is a disorder in which your breathing stops or gets very shallow while you're sleeping. Untreated sleep apnea can raise your chances of having high blood pressure, diabetes, and even a heart attack or stroke.
Stress. Research shows that the most commonly reported "trigger" for a heart attack is an emotionally upsetting event—particularly one involving anger.
Alcohol. Heavy drinking can damage the heart muscle and worsen other risk factors for atherosclerosis. Men should have no more than two drinks containing alcohol a day. Women should have no more than one drink containing alcohol a day.

What Are the Signs and Symptoms of Atherosclerosis?
Atherosclerosis usually doesn't cause signs and symptoms until it severely narrows or totally blocks an artery. Many people don't know they have the disease until they have a medical emergency, such as a heart attack or stroke.

Some people may have other signs and symptoms of the disease. These depend on which arteries are severely narrowed or blocked.

The coronary arteries supply oxygen-rich blood to your heart. When plaque narrows or blocks these arteries (a condition called coronary artery disease, or CAD), a common symptom is angina (AN-ji-na or an-JI-na).

Angina is chest pain or discomfort that occurs when your heart muscle doesn't get enough oxygen-rich blood. Angina may feel like pressure or a squeezing pain in your chest. You also may feel it in your shoulders, arms, neck, jaw, or back.

This pain tends to get worse with activity and go away when you rest. Emotional stress also can trigger the pain.

Other symptoms of CAD are shortness of breath and arrhythmias (irregular heartbeats).

The carotid arteries supply oxygen-rich blood to your brain. When plaque narrows or blocks these arteries (a condition called carotid artery disease), you may have symptoms of a stroke. These symptoms include sudden numbness, weakness, and dizziness.

Plaque also can build up in the major arteries that supply oxygen-rich blood to the legs, arms, and pelvis (a condition called peripheral arterial disease). When these arteries are narrowed or blocked, it can lead to numbness, pain, and sometimes dangerous infections.

How Is Atherosclerosis Diagnosed?
Your doctor will diagnose atherosclerosis based on:

Your medical and family histories
Your risk factors
The results of a physical exam and diagnostic tests
Specialists Involved
If you have atherosclerosis, a doctor, internist, or general practitioner may handle your care. Your doctor may send you to other health care specialists if you need expert care. These specialists may include:

A cardiologist (a doctor who specializes in treating people with heart problems). You may see a cardiologist if you have coronary artery disease (CAD).
A vascular specialist (a doctor who specializes in treating people with blood vessel problems). You may see a vascular specialist if you have peripheral arterial disease (PAD).
A neurologist (a doctor who specializes in treating people with disorders of the nervous system). You may see a neurologist if you've had a stroke due to carotid artery disease.
Physical Exam
During the physical exam, your doctor may listen to your arteries for an abnormal whooshing sound called a bruit (broo-E). Your doctor can hear a bruit when placing a stethoscope over an affected artery. A bruit may indicate poor blood flow due to plaque.

Your doctor also may check to see whether any of your pulses (for example, in the leg or foot) are weak or absent. A weak or absent pulse can be a sign of a blocked artery.

Diagnostic Tests and Procedures
Your doctor may order one or more tests to diagnose atherosclerosis. These tests also can help your doctor learn the extent of your disease and plan the best treatment.

Blood Tests
Blood tests check the levels of certain fats, cholesterol, sugar, and proteins in your blood. Abnormal levels may show that you have risk factors for atherosclerosis.

EKG (Electrocardiogram)
An EKG is a simple test that detects and records the electrical activity of your heart. An EKG shows how fast your heart is beating and whether it has a regular rhythm. It also shows the strength and timing of electrical signals as they pass through each part of your heart.

Certain electrical patterns that the EKG detects can suggest whether CAD is likely. An EKG also can show signs of a previous or current heart attack.

Chest X Ray
A chest x ray takes a picture of the organs and structures inside the chest, including your heart, lungs, and blood vessels.

A chest x ray can reveal signs of heart failure.

Ankle/Brachial Index
This test compares the blood pressure in your ankle with the blood pressure in your arm to see how well your blood is flowing. This test can help diagnose PAD.

This test uses sound waves to create a moving picture of your heart. Echocardiography provides information about the size and shape of your heart and how well your heart chambers and valves are working.

The test also can identify areas of poor blood flow to the heart, areas of heart muscle that aren't contracting normally, and previous injury to the heart muscle caused by poor blood flow.

Computed Tomography Scan
A computed tomography, or CT, scan creates computer-generated images of the heart, brain, or other areas of the body. The test can often show hardening and narrowing of large arteries.

Stress Testing
During stress testing, you exercise to make your heart work hard and beat fast while heart tests are performed. If you can't exercise, you're given medicine to speed up your heart rate.

When your heart is beating fast and working hard, it needs more blood and oxygen. Arteries narrowed by plaque can't supply enough oxygen-rich blood to meet your heart's needs. A stress test can show possible signs of CAD, such as:

Abnormal changes in your heart rate or blood pressure
Symptoms such as shortness of breath or chest pain
Abnormal changes in your heart rhythm or your heart's electrical activity
During the stress test, if you can't exercise for as long as what's considered normal for someone your age, it may be a sign that not enough blood is flowing to your heart. But other factors besides CAD can prevent you from exercising long enough (for example, lung diseases, anemia, or poor general fitness).

Some stress tests use a radioactive dye, sound waves, positron emission tomography (PET), or cardiac magnetic resonance imaging (MRI) to take pictures of your heart when it's working hard and when it's at rest.

These imaging stress tests can show how well blood is flowing in the different parts of your heart. They also can show how well your heart pumps blood when it beats.

Angiography (an-jee-OG-ra-fee) is a test that uses dye and special x rays to show the insides of your arteries. This test can show whether plaque is blocking your arteries and how severe the plaque is.

A thin, flexible tube called a catheter is put into a blood vessel in your arm, groin (upper thigh), or neck. A dye that can be seen on x ray is then injected into the arteries. By looking at the x-ray picture, your doctor can see the flow of blood through your arteries.

How Is Atherosclerosis Treated?
Treatments for atherosclerosis may include lifestyle changes, medicines, and medical procedures or surgery.

Goals of Treatment
The goals of treatment are to:

Relieve symptoms
Reduce risk factors in an effort to slow, stop, or reverse the buildup of plaque
Lower the risk of blood clots forming
Widen or bypass clogged arteries
Prevent diseases related to atherosclerosis
Lifestyle Changes
Making lifestyle changes can often help prevent or treat atherosclerosis. For some people, these changes may be the only treatment needed.

Follow a healthy eating plan to prevent or reduce high blood pressure and high blood cholesterol and to maintain a healthy weight.
Increase your physical activity. Check with your doctor first to find out how much and what kinds of activity are safe for you.
Lose weight, if you're overweight or obese.
Quit smoking, if you smoke. Avoid exposure to secondhand smoke.
Reduce stress.
Follow a Healthy Eating Plan
For a healthy eating plan, go to the National Heart, Lung, and Blood Institute’s (NHLBI’s) Aim for a Healthy Weight Web site. This site provides practical tips on healthy eating, physical activity, and controlling your weight.

Therapeutic Lifestyle Changes (TLC). Your doctor may recommend TLC if you have high cholesterol. TLC is a three-part program that includes a healthy diet, physical activity, and weight management.

With the TLC diet, less than 7 percent of your daily calories should come from saturated fat. This kind of fat is mainly found in meat and poultry, including dairy products. No more than 25 to 35 percent of your daily calories should come from all fats, including saturated, trans, monounsaturated, and polyunsaturated fats.

You also should have less than 200 mg a day of cholesterol. The amounts of cholesterol and the different kinds of fat in prepared foods can be found on the Nutrition Facts label.

Foods high in soluble fiber also are part of a healthy eating plan. They help block the digestive track from absorbing cholesterol. These foods include:

Whole grain cereals such as oatmeal and oat bran
Fruits such as apples, bananas, oranges, pears, and prunes
Legumes such as kidney beans, lentils, chick peas, black-eyed peas, and lima beans
A diet high in fruits and vegetables can increase important cholesterol-lowering compounds in your diet. These compounds, called plant stanols or sterols, work like soluble fiber.

Fish are an important part of a heart healthy diet. They're a good source of omega-3 fatty acids, which may help protect the heart from blood clots and inflammation and reduce the risk for heart attack. Try to have about two fish meals every week. Fish high in omega-3 fats are salmon, tuna (canned or fresh), and mackerel.

You also should try to limit the amount of sodium (salt) that you eat. This means choosing low-sodium and low-salt foods and "no added salt" foods and seasonings at the table or when cooking. The Nutrition Facts label on food packaging shows the amount of sodium in the item.

Try to limit drinks with alcohol. Too much alcohol will raise your blood pressure and triglyceride level. (Triglycerides are a type of fat found in the blood.) Alcohol also adds extra calories, which will cause weight gain. Men should have no more than two drinks containing alcohol a day. Women should have no more than one drink containing alcohol a day.

See the NHLBI’s "Your Guide to Lowering Your Cholesterol With TLC" for more information.

Dietary Approaches to Stop Hypertension (DASH) eating plan. Your doctor may recommend the DASH eating plan if you have high blood pressure. The DASH eating plan focuses on fruits, vegetables, whole grains, and other foods that are heart healthy and lower in salt/sodium.

This eating plan is low in fat and cholesterol. It also focuses on fat-free or low-fat milk and dairy products, fish, poultry, and nuts. The DASH eating plan is reduced in red meats (including lean red meat), sweets, added sugars, and sugar-containing beverages. It's rich in nutrients, protein, and fiber.

The DASH eating plan is a good heart healthy eating plan, even for those who don’t have high blood pressure. See the NHLBI’s "Your Guide to Lowering Your Blood Pressure With DASH" for more information.

Increase Physical Activity
Regular physical activity can lower many atherosclerosis risk factors, including LDL ("bad") cholesterol, high blood pressure, and excess weight. Physical activity also can lower your risk for diabetes and raise your levels of HDL cholesterol (the "good" cholesterol that helps prevent atherosclerosis).

Check with your doctor about how much and what kinds of physical activity are safe for you. Unless your doctor tells you otherwise, try to get at least 30 minutes of moderate-intensity activity on most or all days of the week. You can do the activity all at once or break it up into shorter periods of at least 10 minutes each.

Moderate-intensity activities include brisk walking, dancing, bowling, bicycling, gardening, and housecleaning.

More intense activities, such as jogging, swimming, and various sports, also may be appropriate for shorter periods. See the NHLBI’s "Your Guide to Physical Activity and Your Heart" for more information.

Maintain a Healthy Weight
Maintaining a healthy weight can decrease your risk factors for atherosclerosis. A general goal to aim for is a body mass index (BMI) of less than 25.

BMI measures your weight in relation to your height and gives an estimate of your total body fat. You can calculate your BMI using the NHLBI's online calculator, or your health care provider can calculate your BMI.

A BMI between 25 and 29 is considered overweight. A BMI of 30 or more is considered obese. A BMI of less than 25 is the goal for preventing and treating atherosclerosis. Your doctor or other health care provider can help you determine an appropriate goal for you.

For more information on losing weight and maintaining your weight, see the Diseases and Conditions Index Overweight and Obesity article.

Quit Smoking
If you smoke or use tobacco, quit. Smoking can damage and tighten blood vessels and raise your risk for atherosclerosis.

The U.S. Department of Health and Human Services has information on how to quit smoking.

Reduce Stress
Research shows that the most commonly reported "trigger" for a heart attack is an emotionally upsetting event—particularly one involving anger. Also, some of the ways people cope with stress, such as drinking, smoking, or overeating, aren't heart healthy.

Physical activity can help relieve stress and reduce other atherosclerosis risk factors. Many people also find that meditation or relaxation therapy helps them reduce stress.

To help slow or reverse atherosclerosis, your doctor may prescribe medicines to help lower your cholesterol or blood pressure or prevent blood clots from forming.

For successful treatment, take all medicines as your doctor prescribes.

Medical Procedures and Surgery
If you have severe atherosclerosis, your doctor may recommend one of several procedures or surgeries.

Angioplasty is a procedure to open blocked or narrowed coronary (heart) arteries. Angioplasty can improve blood flow to the heart, relieve chest pain, and possibly prevent a heart attack. Sometimes a small mesh tube called a stent is placed in the artery to keep it open after the procedure.

Coronary artery bypass grafting (CABG) is a type of surgery. In CABG, arteries or veins from other areas in your body are used to bypass (that is, go around) your narrowed coronary arteries. CABG can improve blood flow to your heart, relieve chest pain, and possibly prevent a heart attack.

Bypass grafting also can be used for leg arteries. In this surgery, a healthy blood vessel is used to bypass a narrowed or blocked blood vessel in one of your legs. The healthy blood vessel redirects blood around the artery, improving blood flow to the leg.

Carotid artery surgery removes plaque buildup from the carotid arteries in the neck. This opens the arteries and improves blood flow to the brain. Carotid artery surgery can help prevent a stroke.

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