HEART ATTACK

DEFINITION

A heart attack is caused by the death of, or damage to, part of the heart muscle. Heart attacks usually occur because the supply of blood to the heart muscle is greatly reduced or stopped. A heart attack is also called a myocardial infarction (pronounced my-uh-KAR-dee-al in-FARK-shun).

DESCRIPTION

Heart attack is the leading cause of death in the United States. More than 1.5 million Americans suffer a heart attack each year. About one-third of them die from the heart attack.

The conditions leading to a heart attack often develop over many years. Like all organs in the body, the heart requires a constant supply of blood. It gets that blood from arteries that lead into the heart. In some cases, plaque (pronounced PLAK) may build up on artery walls. Plaque is a collection of cells deposited on the walls of the artery. Over time, the plaque becomes larger and larger. Eventually, it greatly reduces the amount of blood reaching the heart. The plaque can also close off the artery entirely. When that happens, the blood supply to the heart is completely cut off. In such cases, heart cells die and a heart attack occurs.

The prognosis for a heart attack depends greatly on how quickly it is treated. The longer the blood supply is reduced, the more heart muscle cells die.

About one-fifth of all heart attacks are "silent." The patient usually feels no pain. He or she does not realize that a heart attack has occurred. Still, silent heart attacks can cause damage to the heart.

CAUSES

Heart attacks are usually caused by severe coronary artery disease (CAD). CAD is any condition that affects the coronary arteries. The coronary arteries are the blood vessels that supply blood to the heart. Plaque in an artery is a common type of coronary artery disease.

Major Risk Factors

A number of risk factors increase the chance of developing coronary artery disease. Some major risk factors can be changed and others cannot. Among those that cannot be changed are the following:

• Heredity. People whose parents have CAD are more likely to develop the condition. African Americans are also at increased risk for CAD.
• Gender. Men under the age of sixty are more likely to have heart attacks than women of the same age.
• Age. Men over the age of forty-five and women over the age of fifty-five are at higher risk than younger people. People over the age of sixty-five are more likely to die of a heart attack.

Some risk factors that can be changed are:

• Smoking. Smokers are more than twice as likely to have a heart attack than nonsmokers. They are 2 to 4 times more likely to die of a heart attack.
• High cholesterol. Cholesterol is a material that occurs naturally in all animals, including humans. It has many important biological functions. High levels of cholesterol in the blood, however, may increase the chance that plaque will form in blood vessels. It contributes to the risk of CAD and heart attack.
• High blood pressure. High blood pressure (see hypertension entry) makes the heart work harder. Over time, the heart becomes weaker. High blood pressure also increases the risk of stroke, kidney failure, and other types of heart disease.
• Lack of physical exercise. Even modest physical activity can be helpful if done regularly.

Contributing Risk Factors

Other conditions may affect the risk of CAD and heart attack. Scientists are not certain how these factors are involved in these conditions, however. The factors are:

• Diabetes mellitus (see diabetes mellitus entry). People with diabetes are at much higher risk for heart attack. About 80 percent of all diabetics die of some type of heart or blood vessel disease.
• Obesity (see obesity entry). Excess weight places a strain on the heart. It increases the risk of CAD and heart attack.
• Stress and anger. Stress and anger both increase blood pressure and heart rate. Some researchers think that these emotions can contribute to the chance of heart attack.

Most heart attacks are caused by blood clots that form on atherosclerotic plaque, which block a coronary artery from supplying oxygen-rich blood to part of the heart, as highlighted in the illustration above. (Illustration by

Andrew Bezear, Reed business Publishing

. Reproduced by permission of

Science Photo Library and Photo Researchers, Inc.

)

Many of the above risk factors are related to each other. For example, obesity and stress both contribute to high blood pressure. People with more than one risk factor are even more likely to develop CAD and have a heart attack.

SYMPTOMS

More than 60 percent of heart attack patients experience symptoms before the attack actually begins. These symptoms sometimes occur days or weeks ahead of time. Unfortunately, many people do not know the symptoms of heart attack, or they prefer not to recognize those symptoms when they appear. Typical symptoms include:

• Uncomfortable pressure, fullness, squeezing, or pain in the center of the chest. The pain may last for a few minutes, or it may go away and return.
• Pain that spreads to the shoulders, neck, or arms.
• Chest discomfort accompanied by light-headedness, fainting, sweating, nausea, or shortness of breath.

All symptoms do not occur with every heart attack. Symptoms sometimes disappear and then reappear. A person with these symptoms should receive immediate medical attention.

Smokers are more than twice as likely to have a heart attack than nonsmokers and they are 2 to 4 times more likely to die of a heart attack. (© 1998. Reproduced by permission of

Custom Medical Stock Photo

.)

DIAGNOSIS

People who are familiar with heart attacks can usually diagnose the condition simply by looking at a patient. To confirm the diagnosis, the patient's heart rate and blood pressure may be measured. Both an electrocardiogram (pronounced ih-LEK-tro-KAR-dee-o-gram) and blood tests provide further evidence for a heart attack. An electrocardiogram is a test that measures the electrical function of the heart.

TREATMENT

The first stage in treating a heart attack usually involves steps simply to keep the patient alive. If the patient has stopped breathing, cardiopulmonary resuscitation (CPR; pronounced car-dee-oh-PULL-mon-air-ee ree-sus-i-ta-shun) may be needed. CPR may involve breathing into the patient's mouth or pushing on the chest to restore breathing.

Once a patient has reached the hospital, a number of other emergency treatments may be necessary. For example, defibrillation may be required. Defibrillation (pronounced DEE-fib-ri-lay-shun) is used if the patient's heart is beating in an irregular pattern. An electric shock is applied to the patient's chest. The shock causes the heart to stop beating briefly. The heart then begins to beat again, in a more regular pattern.

A patient may also require oxygen therapy. In oxygen therapy, the patient is allowed to breathe air to which extra oxygen has been added. The extra oxygen makes it easier for the heart to work. Oxygen therapy can reduce the damage done to the heart.

Drug Treatments

A variety of drugs may be given following a heart attack. Some examples of these drugs are:

• Thrombolytics. Thrombolytic (pronounced throm-buh-LIH-tik) drugs are chemicals that dissolve blood clots. The most widely used of these drugs is tissue plasminogen activator (tPA). Patients who receive tPA within hours after a heart attack have a greatly increased chance of survival.
• Anticoagulants. Anticoagulants are drugs that thin the blood. Blood thinners reduce the chance that new blood clots will form. Aspirin is one of the most common and most effective blood thinners. Two other blood thinners are warfarin and heparin.
• Pain relief. Nitroglycerin (pronounced nite-roh-GLIS-er-in) tablets are commonly used to treat pain. In more severe cases, morphine may be needed to control pain.

An emergency team giving cardiopulmonary resuscitation (CPR) to a heart attack patient. (© 1992. Reproduced by permission of

Custom Medical Stock Photo

.)

• Tranquilizers. Heart attack patients are often extremely upset. Tranquilizers such as diazepam (pronounced di-AZE-uh-pam, trade name Valium) can help relieve emotional distress.
• Beta-blockers. Beta-blockers slow down the heart rate. They give the heart a chance to start healing. They may also prevent the development of an irregular heart beat.
• Vasodilators. Vasodilators cause blood vessels to open up. This makes it easier for blood to flow through them and reduces the work the heart has to do.
• Drugs that control arrhythmia (pronounced uh-RITH-mee-uh). These drugs help the heart to pump at a regular rate. They reduce the risk that abnormal and potentially fatal irregular heart rhythms may develop.

The key to surviving a heart attack is to open the blood vessels to the heart again. In many cases, thrombolytics and anticoagulants can achieve this goal. When they cannot, surgery may be necessary.

Surgery

Two forms of surgery are often used with heart attack patients. The first is called coronary angioplasty (pronounced AN-jee-o-PLAS-tee). The tool used for coronary angioplasty is a catheter with an empty balloon attached at one end. The catheter is a thin plastic tube that can be inserted into a patient's artery, usually in the thigh or arm. It is then threaded up the artery until it gets to the blocked coronary artery.

At that point, the balloon is inflated. The inflated balloon pushes on the plaque that is blocking the artery and opens up the artery. Blood is able to flow more freely into the heart. The balloon is then deflated, and the catheter removed from the person's body.

Angioplasty is initially successful in about 90 percent of all cases. In about one-third of all cases, the artery narrows again after the procedure. In such cases, the procedure can be repeated.

The second surgical procedure is called bypass surgery. The purpose of bypass surgery is to provide a new pathway for blood to reach the heart. The procedure requires three steps. First, a section of healthy vein is removed from some part of the patient's body, such as a leg or arm. Then a cut is made just below and just above the blockage in the patient's coronary artery. Finally, the healthy vein is attached to the coronary artery. The attached vein provides a new pathway around the blocked section of the artery.

Coronary bypasses are completely successful in about 70 percent of all cases. In another 20 percent of cases, partial relief is obtained. Five years after surgery, the survival rate (the number of patients still alive) for patients who have had a coronary bypass is about 90 percent. It is as high as 80 percent even after ten years.

PROGNOSIS

The aftermath of a heart attack is often severe. Two-thirds of all heart attack patients never recover fully. About one-quarter of all men and nearly one-half of all women who have had heart attacks die within a year. Additional heart attacks are not unusual. About one-quarter of all men and one-third of all women have a second heart attack within six years.

PREVENTION

Some risk factors for heart attack cannot be controlled. There may be hereditary factors that make a person more or less likely to have CAD and a heart attack. However, many risk factors can be managed. Some ways a person can reduce the risk of CAD and heart attack are:

• Eat a healthy diet that includes a variety of foods low in fat, low in cholesterol, and high in fiber. The diet should include plenty of fruits and vegetables, and limited sodium.
• Get regular moderate exercise that lasts for thirty minutes, four or more times per week. Helpful forms of exercise include walking, jogging, cycling, and swimming. Everyday activities, such as active gardening, climbing stairs, and brisk housework, can also help.
• Maintain a proper body weight by watching one's diet and exercising.
• Stop smoking or don't start smoking. People who quit smoking gradually become less at risk for CAD and heart attack.
• Adults should consume only moderate amounts of alcohol. In some adults moderate drinking is not necessarily bad for the body and may even help protect against CAD. Excessive drinking is bad, however, because it raises blood pressure and can produce toxins (poisons) in the body.
• Adopt a more moderate lifestyle that reduces stress and anxiety. This kind of change may contribute to lower blood pressure and reduced risk of CAD and heart attack.
• Take one aspirin tablet per day. Aspirin helps thin the blood and reduce the risk of a blood clot forming.

FOR MORE INFORMATION

Books

American Heart Association. Guide to Heart Attack Treatment, Recovery, Prevention. New York: Time Books, 1996.

American Heart Association. Your Heart: An Owner's Manual. Englewood Cliffs, NJ: Prentice Hall, 1995.

DeBakey, Michael E., and Antonio M. Grotto, Jr. The New Living Heart. Holbrook, MA: Adams Media Corporation, 1997.

McGoon, Michael D. Mayo Clinic Heart Book. New York: William Morrow & Company, 1993.

Notelovitz, Morris, and Diana Tonnessen. The Essential Heart Book for Women. New York: St. Martin's Press, 1996.

Organizations

American Heart Association. National Center. 7272 Greenville Ave., Dallas, TX 75231-4596. (214) 373–6300. http://www.medsearch.com/pf/profiles/amerh.

National Heart, Lung, and Blood Institute Information Center. PO Box 30105. Bethesda, MD 20824-0105. http://www.nhlbi/nibli.htm.

Web sites

"Ask NOAH About: Heart Disease and Stroke." NOAH: New York Online Access to Health. [Online] http://www.noah.cuny.edu/heart_disease/heartdisease.html#H (accessed on October 22, 1999).