Heart attacks result from heart disease — blood vessel disease in the heart. Coronary heart disease (C.H.D.), coronary artery disease (C.A.D.) and ischemic heart disease are more specific names for heart disease.

What causes a heart attack?

The medical term for heart attack is myocardial infarction. A heart attack occurs when the blood supply to part of the heart muscle itself, the myocardium, is severely reduced or stopped. This occurs when one of the arteries that supply blood to the heart muscle (coronary arteries) is blocked by an obstruction. The blockage is sometimes from the buildup of plaque (deposits of fat-like substances) due to atherosclerosis.

A heart attack also can be caused by a blood clot lodged in a coronary artery. Such an event is sometimes called a coronary thrombosis or coronary occlusion. A myocardial infarction is the damaging or death of an area of the heart muscle resulting from a reduced blood supply to that area.

If the blood supply is cut off severely or for a long time, muscle cells suffer irreversible injury and die. Disability or death can result, depending on how much heart muscle is damaged.

Sometimes a coronary artery temporarily contracts or goes into spasm. When this happens the artery narrows and blood flow to part of the heart muscle decreases or even stops. What causes a spasm is unclear. But it can occur in normal-appearing blood vessels as well as vessels partly blocked by atherosclerosis. If a spasm is severe, a heart attack may result.

Heart Attack Symptoms / Warning Signs

IF YOU THINK YOU ARE HAVING A HEART ATTACK, CALL YOUR EMERGENCY MEDICAL SYSTEM IMMEDIATELY.

The American Heart Association says the body likely will send one or more of these "classic" warning signals of a heart attack:

• Uncomfortable pressure, fullness, squeezing or pain in 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.
  

• 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.
  

How do I know if a heart attack has occurred?

The actual diagnosis of a heart attack must be made by a doctor who has studied the results of several tests.

The doctor will:

• Review the patient's complete medical history.
  
• Give a physical examination.
  
• Use an electrocardiogram to discover any abnormalities caused by damage to the heart.
  
• Sometimes use a blood test to detect abnormal levels of certain enzymes in the bloodstream.
  

AHA Recommendation

When a heart attack occurs, it's critical to recognize the signals and respond immediately. About half of all heart attack victims wait two hours or longer before deciding to get help. This reduces their chance of survival, because delay in the early phases increases the risk of sudden death. It also lessens the chance of preserving heart muscle, which raises the risk of disability for those who survive.

Time is critical. Anyone experiencing the warning signals of a heart attack should be taken immediately to the nearest hospital with 24-hour emergency cardiac care. People who become unconscious before reaching the emergency room may receive cardiopulmonary resuscitation (CPR).

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