Coronary artery disease is a condition in which fatty deposits accumulate in the cells lining the wall of a coronary artery and obstruct the blood flow.

Fatty deposits (plaques) build up gradually and are scattered in the large branches of the two main coronary arteries, which encircle theheart and supply it with blood; this gradual process is known as stherosclerosis. The fatty deposits bulge into the arteries, narrowing them. As the fatty deposits enlarge, portions may rupture and enter the bloodstream, or small blood clots may form on their surfaces.

For the heart to contract and pump blood normally, the heart muscle requires a continuous supply of oxygen-enriched blood from the coronary arteries. But as an obstruction of a coronary artery worsens, ischemia (inadequate blood supply) to the heart muscle can develop, causing heart damage. The most common cause of inadequate blood supply to the heart is coronary artery disease. The major complications of coronary artery disease are angina and heart attack (myocardial infarction).

ANGINA

Angina, also called angina pectoris, is temporary chest pain or a sensation of pressure that occurs while the heart muscle isn't receiving enough oxygen.
The heart's oxygen needs are determined by how hard the heart is working - how fast the heart is beating and how strong the beats are. Physical exertion and emotions make the heart work harder and thus increase the heart's oxygen needs. When the arteries are narrowed or blocked so that blood flow to the muscle can't increase to meet the need for more oxygen, there may be an inadequate blood supply, resulting in pain.

Not everyone with an inadequate blood supply experiences angina. An inadequate blood supply without angina is called silent ischemia.
Typically, angina is triggered by physical activity, lasts no more than a few minutes, and subsides with rest. Emotional stress may also cause or worsen angina.

About 6,400,000 Americans have angina pectoris - 2,300,000 males and 4,000,000 females. About 400,000 new cases of stable angina (predictable chest pain on exertion or under mental or emotional stress) and about 150,000 new cases of unstable angina (unexpected chest pain while at rest) occur each year.

SYMPTOMS OF ANGINA

• pressure or ache beneath the sternum (breastbone)
• pain also may occur in the left shoulder or down the inside of the left arm; through the back; in the throat, jaw, or teeth; and occasionally down the right arm
• many people describe the feeling as discomfort rather than pain

HEART ATTACK

Heart attack is a medical emergency in which some of the heart's blood supply is suddenly severly restricted or cut off, causing heart muscle to die from lack of oxygen.

The heart's ability to keep pumping after a heart attack is directly related to the extent and location of the damaged tissue. Because each coronary artery supplies a specific section of the heart, the location of the damage is determined by which artery is blocked. If more than half of the heart tissue is damaged, the heart generally can't function, and severe disability or death is likely. Even when damage is less extensive, the heart may be unable to pump adequately, resulting in heart failure or shock - an even more serious condition.

A blood clot is the most common cause of a blocked coronary artery. Usually, the artery is already partially narrowed by fatty deposits (atheromas). An atheroma may rupture or tear and create more blockage, which promotes clot formation. The ruptured atheroma not only restricts the flow of blood through an artery, but also makes platelets stickier, further encouraging clots to form.

SYMPTOMS OF HEART ATTACK

• uncomfortable pressure, fullness, squeezing or pain in the center of the center of the chest lasting more than a few minutes
• pain spreading to the shoulders, neck or arms
• chest discomfort with lightheadedness, fainting, sweating, nausea or shortness of breath

LESS COMMON WARNING SIGNS OF HEART ATTACK

• atypical chest pain, stomach or abdominal pain
• nausea or dizziness
• shortness of breath and difficulty breathing
• unexplained anxiety, weakness or fatigue
• palpitations, cold sweat or paleness

DIAGNOSIS

A doctor diagnoses angina largely by a person's description of the symptoms. Between and even during attacks of angina, a physical examination or an ECG may reveal little, if anything, abnormal. During an attack, the heart rate may increase slightly, blood pressure may go up, and a doctor may hear a characteristic change in the heartbeat while listening with a stethoscope. During an attack of typical angina, a doctor may detect changes in the ECG, but the ECG may be normal between episodes, even in a person with extensive coronary artery disease.

When symptoms are typical, the diagnosis is usually easy for a doctor. The kind of pain, its location, and its association with exertion, meals, weather, and other factors may help a doctor make the diagnosis. Certain tests may help determine the severity of the ischemia and the presence and extent of coronary artery disease.

EXERCISE TOLERANCE TESTING (a test in which the person walks on a treadmill while being monitored by an ECG) can help in evaluating the severity of coronary artery disease and the ability of the heart to respond to ischemia. The results also may help determine the need for coronary arteriography or surgery.

RADIONUCLIDE IMAGING combined with exercise tolerance testing may provide a doctor with valuable information about a person's angina. Radionuclide imaging not only confirms the presence of an inadequate blood supply but also identifies the region and amount of heart muscle affected and shows the amount of blood flow reaching the heart muscle.

EXERCISE ECHOCARDIOGRAPHY is a test in which images (echocardiograms) are obtained by bouncing ultrasound waves off the heart. The test is harmless and shows heart size, movement of the heart muscle, blood flow through the heart valves, and valve function. Echocardiograms are obtained at rest and at peak exercise. When there is an inadequate blood supply, the pumping motion of the wall of the left ventricle is abnormal.

CORONARY ARTERIOGRAPHY may be performed when a diagnosis of coronary artery disease or an inadequate blood supply isn't certain. However, most commonly, this test is used to determine the severity of coronary artery disease and to help evaluate whether the person needs a procedure to improve blood flow - either coronary artery bypass surgery or angioplasty.

ANGIOGRAPHY (movie-type x-rays of arteries taken after a dye is injected) sometimes can detect spasm in coronary arteries that don't have an atheroma. Sometimes, certain drugs are given to produce the spasm during angiography.

ULTRAFAST CT is a non-invasive imaging technique. This radiology study identifies coronary artery cholesterol plaques by the presence of calcium in the plaques.

VASCULAR ULTRASOUND is another imaging technique which evaluates the arteries in the neck. This is useful because patients with cholesterol build-up in arteries in the neck and legs also tend to have cholesterol plaques in the coronary arteries.

Whenever a man over age 35 or a woman over age 50 complains of chest pain, a doctor usually considers the possibility of heart attack. An electro cardiogram and certain blood tests can usually confirm the diagnosis of a heart attack in a few hours. If these tests don't provide enough information, an echocardiogram or radionuclide imaging may be done.

TREATMENT OF ANGINA

Treatment begins with attempts to prevent coronary artery disease, to slow its progression, or to reverse it by dealing with its know causes (risk factors). Primary risk factors, such as elevated blood pressure and elevated cholesterol levels, are treated promptly. Cigarette smoking is the most important preventable risk factor in coronary artery disease.

Treatment of angina depends partially on the severity and stability of the symptoms. When symptoms are stable and mild to moderate, reducing risk factors and using drugs may be most effective. When symptoms get worse rapidly, immediate hospitalization and drug treatment are usual. If the symptoms don't markedly subside with drug treatment, diet and lifestyle changes, angiography may be used to determine if coronary artery bypass surgery or angioplasty is feasible.

DRUG TREATMENT:

Beta-blockers reduce resting heart rate, nitrates (such as nitroglycerin) dilate the walls of the blood vessels. (beta-blockers and nitrates have been shown to reduce heart attacks and sudden death, improving the long-term outcome in people with coronary artery disease). Calcium antgagonists prevent the blood vessels from constricting and can counter artery spasm, and some may slow the heart rate. Antiplatelet drugs such as Aspirin bind irreversibly to platelets and keep them from clumping on blood vessel walls.

SURGICAL TREATMENT:

CORONARY ARTERY BYPASS SURGERY is most likely to benefit a person who has severe angina that hasn't improved with drug therapy, a normally functioning heart, and no previous heart attacks. Nonemergency surgery of this sort carries a risk of death of 1% or less and a chance of heart damage (i.e. heart attack) during surgery of less than 5%. About 85% of patients have complete or dramatic relief of symptoms with surgery.

Bypass surgery consists of grafting veins or arteries from the aorta (a major artery that takes blood from the heart to the rest of the body) to the coronary artery, thus skipping over (bypassing) the obstructed area. The veins are usually taken from the leg. Most surgeons also use at least one artery as a graft. The artery is usually taken from beneath the sternum (breastbone). These arteries rarely develop coronary artery disease, and more than 90% of them still work properly 10 years after bypass surgery.

CORONARY ANGIOPLASTY: The reasons people with coronary artery disease have angioplasty are similar to the reasons they have bypass surgery. Not all coronary artery obstructions are suited to angioplasty because of their location, length, degree of calcification, or other conditions.

The procedure begins with a puncture of a larger peripheral artery, usually the femoral artery in the leg, with a large needle. Then a long guide wire is threaded through the needle and into the arterial system, through the aorta and into the obstructed coronary artery. A catheter with a balloon attached to the tip is threaded over the guide wire and into the diseased coronary artery. The catheter is positioned so that the balloon is at the level of the obstruction. The balloon is then inflated for several seconds. Inflation and deflation may be repeated several times. The inflated balloon compresses the obstructing atheroma, distends the artery, and partially tears the inner layers of the arterial wall. When angioplasty is successful, the obstruction is greatly reduced.

In about 40 percent of patients, the artery clogs again. Sometimes blood thinners are also prescribed along with the surgery to improve blood flow. Doctors have begun inserting small metal coils called stents (stainless steel screen-like tube), after the balloon is inserted, to keep the passages open longer.

Studies show that stents reduced bypass surgery rates by 50% in the mid-1990s, and hospital death rates by 15%.

TREATMENT OF HEART ATTACK

A heart attack is a medical emergency. Half of the deaths from heart attacks occur in the first 3 or 4 hours after symptoms begin. The sooner treatment begins, the better the chances of survival.

Usually, a person is immediately given an aspirin tablet to chew. This reduces the clot in the coronary artery. A beta-blocker may be given to slow the heart rate and make the heart work less hard to pump blood through the body.

Often, oxygen is given which increases the oxygen pressure in the blood, which provides more oxygen to the heart and keeps heart tissue damage to a minimum.

Thrombolytic therapy drugs are given intravenously to dissolve bloodclots within 6 hours of the start of heart attack symptoms. After 6 hours, some damage is permanent, and removing the blockage probably doesn't help.

Some cardiovascular treatment centers use angioplasty or coronary artery bypass surgery right after the heart attack instead of thrombolytic therapy.

PROGNOSIS OF ANGINA

Key factors in predicting what may happen to people who have angina include age, the extent of coronary artery disease, the severity of symptoms, and most of all, the degree of normal heart muscle function. The more coronary arteries affected or the worse the blockage of the arteries, the poorer the prognosis. The prognosis is surprisingly good in a person with stable angina and normal pumping ability (ventricular muscle function). Reduced pumping ability dramatically worsens the outlook.

PROGNOSIS OF HEART ATTACK

Most people who survive for a few days after a heart attack can expect a full recovery, but about 10% die within a year. Most deaths occur in the first 3 or 4 months, typically in people who continue to have angina, ventricular arrhythmias, and heart failure.

After a heart attack, a doctor and patient should discuss risk factors that contribute to coronary artery disease, especially ones the patient can change. Quitting smoking, losing weight, controlling blood pressure, reducing blood cholesterol levels through diet or medication, and performing daily aerobic exercises all help reduce the risk of coronary artery disease.

U.S. STATISTICS

Coronary artery disease is the leading cause of death among Americans. It caused 459,841 deaths in the United States in 1998 - 1 of every 5 deaths. It is the single largest killer of American males and females. The Center for Disease Control estimates that 12.4 million people have the disease. About every 29 seconds an American will suffer a coronary event, and about every minute someone will die from one. 85% of people who die of coronary artery disease are age 65 or older. About 80% of coronary artery disease mortality in people under age 65 occurs during the first attack. In part because women have heart attacks at older ages than men do, they're more likely to die from them within a few weeks.

The risk of developing heart disease for those age 40 and older is one in two for men and one in three for women in the United States. A 50-year-old woman is three times more likely to develop heart disease than breast cancer in her lifetime. While she has a 31% risk of heart disease, she has an 11% chance of getting breast cancer.

Aggressive prevention efforts - such as reducing and controlling high blood pressure, cholesterol and diabetes; eating a low-fat diet and increasing consumption of fruits and vegetables; and participating in moderate physical activity - are key to reducing coronary heart disease deaths.

CHOLESTEROL AND CORONARY ARTERY DISEASE

The risk of coronary artery disease increases with elevated levels of total cholesterol and low-density lipoprotein cholesterol (LDL cholesterol or bad cholesterol) in the blood. The risk of coronary artery disease decreases with elevated levels of high-density lipoprotein cholesterol (HDL cholesterol or good cholesterol).

Diet influences the total cholesterol level - and thus the risk of coronary artery disease. The typical American diet increases total cholesterol levels. Changing the diet (and taking prescribed drugs if needed) can lower cholesterol levels. Lowering levels of total cholesterol and bad cholesterol slows or reverses the progress of coronary artery disease.

The benefits of lowering levels of bad cholesterol are greatest in patients with other risk factors of coronary artery disease. These risk factors included cigarette smoking, high blood pressure, obesity, inactivity, high triglyceride levels, a genetic predisposition, and male steroids (androgens). Quitting smoking, lowering blood pressure, losing weight, and increasing exercise decrease the risk of coronary artery disease.

SOURCES

American Heart Association
Heart Information Network
Centre for Disease Control