General Characteristics of Heart Attacks
Each year, more than a million Americans suffer a heart attack. Although heart disease remains the leading cause of
death in the United States, great strides have been made in the last decade, both in treating heart attacks and in
helping people who have suffered one resume a full, active life.
The most common type of heart attack is caused by a coronary thrombosis, which occurs when a clot (thrombus) blocks
one or more of the blood vessels that nourish the heart muscle. As a result of the lack of blood, part of the muscle
may be damaged, and its ability to contract may be lost. This is known as a myocardial infarction. If the infarct
is small and the electrical impulses that control the heart's contractions (beats) are not disturbed, chances for
recovery are excellent.
Coronary Artery Disease
Coronary thrombosis is one of the manifestations of coronary artery disease. As we grow older, our blood vessels
tend to lose their elasticity, a process known as arteriosclerosis. The arteries may also become narrowed or clogged
with deposits of fatty material called atheromas, a condition called atherosclerosis. Atherosclerosis is progressive
and usually does not produce symptoms until there is significant blockage in the blood flow. Sometimes, in fact,
the first symptom of this heart disease is a heart attack.
Although the specific cause of atherosclerosis is not known, it has been found that certain risk factors help in
identifying population groups that are more likely to develop it. Three major risk factors are high levels of
cholesterol and other blood fats, high blood pressure (hypertension) and cigarette smoking. Others include diabetes,
obesity, a sedentary life style, aging, being male and heredity.
Atherosclerosis begins forming as a fatty streak on the inner wall of an artery, usually at its branching-out point,
and disturbs the smooth flow of blood. As patches of fatty tissue build up, the inner wall becomes narrower, which
inhibits blood flow in a more significant way. An artery continues to narrow as the tissue buildup progresses, and in
time, the fatty deposit becomes a hard mass of fatty tissue with a tough outer lining of cells - a plaque. As plaques
spread and thicken, they erode the wall of the artery, which interferes with blood flow and makes it increasingly
turbulent. This turbulence may trigger the blood to form a clot (thrombus), partially or completely blocking the
artery. Further, a fragment of the clot (embolus) may be carried by the bloodstream and block an artery at some distant,
narrower point.
Heart attacks sometimes occur in people with little or no coronary artery disease. Some experts believe that a spasm
or sudden constriction of the coronary artery may be the cause of these heart attacks. It appears that a spasm may
occur in a coronary artery that is totally free of atherosclerosis (as well as in one that is heavily affected by that
condition), and this would explain why many people suffer angina and other cardiac problems without any evidence of
underlying blockage in the arteries.
