Coronary artery disease
Coronary artery disease, also called coronary heart disease or heart disease,is the leading cause of death for both men and women in the United States.
Coronary artery disease occurs when the coronary arteries become partially blocked or clogged. This blockage limits the flow of blood from the coronary arteries, the major arteries supplying oxygen-rich blood to the heart. The coronary arteries expand when the heart is working harder and needs more oxygen.If the arteries are unable to expand, the heart is deprived of oxygen (myocardial ischemia). When the blockage is limited, chest pain or pressure called angina may occur. When the blockage cuts off the flow of blood, the result isheart attack (myocardial infarction or heart muscle death).
Healthy coronary arteries are clean, smooth, and slick. The artery walls areflexible and can expand to let more blood through when the heart needs to work harder. The disease process in arteries is thought to begin with an injuryto the linings and walls of the arteries. This injury makes them susceptibleto atherosclerosis and blood clots (thrombosis).
Coronary artery disease is usually caused by atherosclerosis. Cholesterol andother fatty substances accumulate on the inner wall of the arteries. They attract fibrous tissue, blood components, and calcium and harden into artery-clogging plaques. Atherosclerotic plaques often form blood clots that can alsoblock the coronary arteries (coronary thrombosis). Congenital defects and muscle spasms, too, can block blood flow. Recent research indicates that infection from organisms such as chlamydia bacteria may be responsible for some cases of coronary artery disease.
A number of major contributing factors increase the risk of developing coronary artery disease. Some of these can be changed and some cannot. People withmore risk factors are more likely to develop coronary artery disease.
Risk factors that cannot be changed include heredity, sex, and age. For example, people whose parents have coronary artery disease are more likely to develop it. African-Americans are also at increased risk because they experiencea higher rate of severe hypertension than whites do. Men are more likely to have heart attacks than women are and to have them at a younger age. Over age60, however, women have coronary artery disease at a rate equal to that of men. Occasionally, coronary disease may strike a person in the 30s. Older people (those over 65) are more likely to die of a heart attack. Older women are twice as likely as older men to die within a few weeks of a heart attack.
Other risk factors can be changed. For example, smoking increases both the chance of developing coronary artery disease and the chance of dying from it. Smokers are two to four times more likely than are nonsmokers to die of suddenheart attack. Second hand-smoke may also increase risk. Dietary sources of cholesterol are meat, eggs, and other animal products. The body also producesit. Age, sex, heredity, and diet affect one's blood cholesterol. The risk ofdeveloping coronary artery disease increases steadily as blood cholesterol levels increase above 160 mg/dL (milligrams per deciliter). When a person has other risk factors, the risk multiplies.
High blood pressure makes the heart work harder and weakens it over time. Itincreases the risk of heart attack, stroke, kidney failure, and congestive heart failure. In combination with obesity, smoking, high cholesterol, or diabetes, high blood pressure raises the risk of heart attack or stroke several times.
Lack of exercise increases the risk of coronary artery disease. Even modest physical activity, like walking, is beneficial if done regularly.
The risk of developing coronary artery disease is seriously increased for diabetics. More than 80% of diabetics die of some type of heart or blood vesseldisease.
Other risk factors such as obesity and stress and anger have been linked to coronary artery disease, but their significance is not known yet.
Chest pain (angina) is the main symptom of coronary heart disease but it is not always present. Other symptoms include shortness of breath, and chest heaviness, tightness, pain, a burning sensation, squeezing, or pressure either behind the breastbone or in the arms, neck, or jaws. Many people have no symptoms of coronary artery disease before having a heart attack.
Diagnostic tests for coronary artery disease measure weight, blood pressure,blood lipid levels, and fasting blood glucose levels. Other diagnostic testshelp to confirm the diagnosis.
An electrocardiogram (ECG) shows the heart's activity and may reveal a lack of oxygen (ischemia). But a definite diagnosis cannot be made from electrocardiography. About 50% of patients with significant coronary artery disease havenormal resting electrocardiograms. Another type of electrocardiogram, knownas the exercise stress test, measures how the heart and blood vessels respondto exertion when the patient is exercising on a treadmill or a stationary bike. It sometimes gives a normal reading when the patient has a heart problemor an abnormal reading when the patient does not.
If the electrocardiogram reveals a problem or is inconclusive, the next stepis exercise echocardiography or nuclear scanning (angiography), which uses sound waves to create an image of the heart's chambers and valves. It does notreveal the coronary arteries themselves but can detect abnormalities in heartwall motion caused by coronary disease.
Radionuclide angiography enables physicians to see the blood flow of the coronary arteries. Nuclear scans are performed by injecting a small amount of radiopharmaceutical such as thallium into the bloodstream. A scanning camera passes back and forth over the patient who lies on a table. Thallium scanning isusually done in conjunction with an exercise stress test. When the stress test is finished, thallium or sestamibi is injected. The patient resumes exercise for one minute to absorb the thallium.
Coronary angiography is the most accurate method for making a diagnosis of coronary artery disease, but it is also the most invasive. It is a form of cardiac catheterization that shows the heart's chambers, great vessels, and coronary arteries using x-ray technology.
Coronary artery disease can be treated many ways. The choice of treatment depends on the severity of the disease. Treatments include lifestyle changes anddrug therapy, percutaneous transluminal coronary angioplasty, and coronary artery bypass surgery. Coronary artery disease is a chronic disease requiringlifelong care. Angioplasty or bypass surgery is not a "cure."
People with less severe coronary artery disease may gain adequate control through lifestyle changes and drug therapy. Many of the lifestyle changes that prevent disease progression--a low-fat, low-cholesterol diet, weight loss if needed, exercise, and not smoking--also help prevent the disease from developing.
Drugs such as nitrates, beta-blockers, and calcium-channel blockers relieve chest pain and complications of coronary artery disease, but they cannot clearblocked arteries. Nitrates (nitroglycerin) improve blood flow to the heart.Beta-blockers (acebutelol, propranolol) reduce the amount of oxygen requiredby the heart during stress. One type of calcium-channel blocker (verapamil, diltiazem hydrochloride) helps keep the arteries open and reduces blood pressure. Aspirin helps prevent blood clots from forming on plaques, reducing the likelihood of a heart attack. Cholesterol-lowering medications are also indicated in most cases.
Percutaneous transluminal coronary angioplasty and bypass surgery are procedures that enter the body (invasive procedures) to improve blood flow in the coronary arteries. Percutaneous transluminal coronary angioplasty, usually called coronary angioplasty, is a nonsurgical procedure. It is successful about 90% of the time, but for one-third of patients the artery narrows again withinsix months. The procedure can be repeated. It is less invasive and less expensive than coronary artery bypass surgery.
In coronary artery bypass surgery, a healthy artery or vein from an arm, leg,or chest wall is used to build a detour around the coronary artery blockage.The healthy vessel then supplies oxygen-rich blood to the heart. Bypass surgery is major surgery. It is appropriate for those patients with blockages intwo or three major coronary arteries, those with severely narrowed left maincoronary arteries, and those who have not responded to other treatments.
Three semiexperimental surgical procedures for unblocking coronary arteries are currently being studied. Atherectomy is a procedure in which the cardiologist shaves off and removes strips of plaque from the blocked artery. In laserangioplasty, a catheter with a laser tip is inserted into the affected artery to burn or break down the plaque. A metal coil called a stent can be implanted permanently to keep a blocked artery open. Stenting is becoming more common.
In many cases, coronary artery disease can be successfully treated. Advancesin medicine and healthier lifestyles have caused a substantial decline in death rates from coronary artery disease since the mid-1980s. New diagnostic techniques enable doctors to identify and treat coronary artery disease in its earliest stages. New technologies and surgical procedures have extended the lives of many patients who would otherwise have died. Research on coronary artery disease continues.
A healthy lifestyle can help prevent coronary artery disease and help keep itfrom progressing. A heart-healthy lifestyle includes eating right, regular exercise, maintaining a healthy weight, no smoking, moderate drinking, no recreational drugs, controlling hypertension, and managing stress. Cardiac rehabilitation programs are excellent to help prevent recurring coronary problems for people who are at risk and who have had coronary events and procedures.