Jeanne Sullivan, age 12, of Columbia, Tenn., for her question:
WHAT ACTUALLY CAUSES A HEART ATTACK?
Almost all heart attacks are caused by a clot of blood blocking a coronary artery that has become hard and narrow. Such a blockage is called a coronary thrombosis.
A heart attack usually occurs suddenly. But it is actually caused by a buildup of fatty deposits and calcium in the coronary arteries that has occurred slowly over a long period of time. Sometimes it may take years before an artery is narrow enough to be sealed off by a blood clot.
There is no single cause of heart attacks or arteriosclerosis, the condition in which the arteries harden. Several factors are involved, usually involving diet, hereditary and sometimes smoking.
The fatty deposits that coat the inside of arteries contain large amounts of a substance called cholesterol. High levels of cholesterol form in the bodies of persons whose diets are rich in animal fats.
Foods rich in animal fats include meat, butter, cheese, cream and whole milk. Persons who eat a lot of such foods are more likely to suffer a heart attack through arteriosclerosis than those whose diets are low in animal fats. As a result, many doctors tell their patients to replace most of the animal fats in their diets with vegetable oils.
Hereditary traits may play a part in heart attacks by making a person more susceptible to arteriosclerosis. On the other hand, a person aware of a family history of arteriosclerosis is often more likely to take care of his heart with a proper diet.
Many medical experts say that a person's habits and his environment are far more important factors in heart attacks than any traits he may inherit from parents.
Medical experts also say that persons who smoke cigarettes are two to three times more likely to have heart attacks than non smokers or former smokers.
Doctors also say that while smoking does not actually cause heart attacks, it very definitely increases the likelihood of an attack.
In a heart attack, the clot cuts off the blood supply to part of the heart and then a portion of the heart muscle dies. If the clot blocks a major artery, cutting off the blood supply to a large area of the heart, the attack is usually fatal.
About 40 percent of the persons who suffer a heart attack die shortly afterwards. However, in the majority of cases, the patient recovers.
Sometimes the blood clot may not block a major artery, and only a small portion of the patient's heart may be involved. The patient's body eventually replaces the dead heart muscle with scar tissue, and smaller arteries take over the job of supplying the scar tissue with blood.