What is a heart attack?

A heart attack occurs when a blood vessel in the heart (coronary artery) becomes blocked and cuts off the blood supply to the heart muscle, causing that area of the heart to die.

Myocardial infarction (MI) is the medical term for a heart attack.

How does it occur?

A heart attack can occur at any time and often occurs without warning. The coronary arteries can become narrowed by the buildup of cholesterol plaque over many years. As the arteries become narrow, less blood can go through them, so less oxygen gets to the heart muscle. The process of narrowing is called atherosclerosis. The narrower the artery becomes, the more likely it is that a blood clot may form and block the artery completely, causing a heart attack. Sometimes blockages can occur suddenly even in places where the artery was not narrow before.

A heart attack sometimes occurs when the heart muscle suddenly needs more oxygen. This might happen, for example, during hard exercise such as shoveling snow, or when your blood pressure suddenly increases. This increased oxygen need is also thought to be the reason cocaine abuse causes chest pain, heart attack, and sudden death.

The lack of blood and oxygen during a heart attack damages the heart muscle. Part of the heart muscle may die. The more heart muscle that dies, the more likely it is that disability or death will result. If only a small amount of heart muscle dies, the odds of surviving and living normally afterward are high. Early treatment of heart attacks is critical to try to unblock the arteries and limit the amount of muscle death. However, death may quickly result from a heart attack, regardless of the size of the area affected by the blockage.

Heart attacks can cause death in several ways:

• If too much muscle dies, the heart cannot pump enough blood to the rest of the body.

• The muscular wall of the heart can tear as a result of muscle death, allowing all of the blood to leak out.

• If the heart cells that regulate the heartbeat are injured or dying, the heart may stop beating or beat too fast to pump effectively.

You are more likely to have a heart attack as you get older. Heart attacks are more likely to occur at a younger age in men than in women. Female hormones tend to help protect women until menopause, when the body produces less of these hormones. Heart disease is more likely to be correctly diagnosed in men and less likely to be suspected in women.

Risk factors for heart disease include:

• cigarette smoking

• a family history of heart attack

• diabetes

• overweight

• high blood pressure

• high blood cholesterol

• low HDL cholesterol (that is, too little 'good' cholesterol)

• stress, especially chronic anger or hostility

• a lifestyle that does not include much physical activity.

What are the symptoms?

You may feel pressure or pain in the middle of your chest. The pain may extend into your shoulder and arm or into your abdomen or jaw. The pain may be severe. (Some people think they have indigestion and do not get medical help as soon as they should.)

Other typical symptoms that often occur with the chest pain are:

• shortness of breath

• sweating

• nausea or vomiting

• weakness or lightheadedness

• paleness.

In severe cases, sudden death may occur.

How is it diagnosed?

The doctor examines you and asks about your immediate symptoms and your medical history. He or she may use the following tests:

• A heart monitor can show your pulse as well as abnormal heart rates or rhythms.

• An ECG (electrocardiogram) measures and records the electrical activity of your heart. It gives information about areas of heart muscle that are damaged.

• Your blood oxygen level can be monitored by a sensor that is attached to your finger or ear.

• Blood tests are used to find out whether the heart muscle has been damaged.

• A chest x-ray can show abnormal heart size and signs of heart failure (poor pumping by the heart).

• A stress test is an ECG done while you exercise on a treadmill or stationary bicycle. This test shows whether the heart is getting enough blood and how well the heart tolerates exercise.

• Doppler ultrasound (echocardiogram) is a type of scan used to examine your heart valves, muscles, and blood flow, and to look at how efficiently your heart is pumping.

• A coronary angiogram (cardiac catheterization) is a special x-ray procedure used to find out which blood vessel is blocked and how severely.

These tests may be done in the hospital and after you leave the hospital.

How is it treated?

Heart attacks are treated in the hospital in order to watch for problems, such as abnormal heart rhythm, that can occur within hours or days of a heart attack and may need immediate treatment. You may stay in the hospital for about 2 to 7 days. You may be in a special intensive care unit for heart patients.

Your doctor may use medication to:

• reduce your pain

• stabilize your heart rhythm

• make it easier for you to breathe

• lower your blood pressure

• prevent further damage to your heart

• dissolve blood clots.

The exact treatment you receive depends on how you feel, how much heart muscle is damaged, and how much the arteries in your heart are blocked or narrowed. Many times, people who have had a heart attack need surgery or other procedures, such as balloon angioplasty, to improve blood flow to the heart. This may mean a longer stay in the hospital.

You may have a stress test before you leave the hospital. The results of this test may help your doctor decide what treatments are best for you or may be needed in the future.

After you leave the hospital your doctor may have you wear a small, portable ECG recorder, called a Holter monitor, for 24 hours. The Holter monitor can show whether your heartbeat is irregular during certain activities.

After a heart attack, almost everyone begins a rehabilitation program. This involves a gradual and closely monitored exercise program, as well as education about diet and other ways to improve your health and prevent more heart attacks in the future.

How can I take care of myself?

Follow the treatment plan your doctor prescribes. In addition:

• Eat healthy food that is low in fat and sodium.

• Lose weight if you need to, and maintain the lower weight.

• Take it easy at first.

• Exercise regularly, according to your doctor's instructions.

• Talk with your doctor about any questions or fears you may have.

• Carry your medication with you and know how to take it properly. A list of the names and doses and instructions for taking each medicine can be helpful to have.

How can I help prevent a heart attack?

Follow these guidelines:

• Stop smoking.

• Exercise according to your doctor's prescription.

• Try to achieve and stay at the weight your doctor recommends.

• Try to keep your cholesterol at a normal level.

• Follow your doctor's instructions for medication and follow-up appointments.

If you get chest pain, call 911. Immediate emergency care improves your chances of survival and of avoiding damage to your heart.