As an active muscle, the heart needs a continuous supply of oxygen. The coronary arteries have the job of carrying oxygen to the heart. These arteries have a difficult job to do because they undergo intense compression every time the heart beats. This job becomes even more difficult when the arteries are damaged by
(commonly, though not quite accurately, called “hardening of the arteries”) in a condition called
coronary artery disease
In coronary artery disease the passages inside the coronary arteries become narrowed by plaque deposits, which decreases blood flow. When the blood flow is decreased to a sufficient extent, pain caused by oxygen deprivation occurs. This pain is known as
. Angina tends to wax and wane, generally worsening with exercise.
A heart attack may occur after years of angina, or with no warning at all. Most heart attacks occur when a blood clot (thrombus) forms on the roughened wall of an atherosclerotic coronary artery. Such a blood clot may lead to a sudden and complete blockage of the artery. More rarely, a spasm of a coronary artery may cut off blood flow. In either case, the cells of the heart fed by that artery begin to die. The region of dead cells is called an infarct, leading to the technical name for a heart attack: a myocardial infarction (MI).
The classic symptom of a heart attack is intense, central chest pressure. Other common symptoms include: pain or heaviness in the left arm, nausea, shortness of breath, increased perspiration, and a feeling of impending doom. However, many people who have had an MI describe chest "discomfort," or pain in the jaw, teeth, arm, or abdomen. Women are more likely than men to feel pain in their backs. Often, symptoms come on gradually and are intermittent or vague. A quarter of patients—more often women and people with diabetes—experience no symptoms at all.
When a heart attack occurs, emergency treatment at a hospital can minimize the extent of permanent damage to the heart. “Clot busting” drugs, if given soon enough, can open the coronary arteries, allowing blood to flow again. Other methods of restoring blood flow include procedures known as angioplasty, stenting, and bypass surgery. The aim is to save those heart cells that are in danger of dying but are still hanging on to life. Recovery after a heart attack depends on the extent of heart damage. If only a small portion of the heart has died, or if it is in a relatively less important region, symptoms may be slight. More severe damage can cause the heart to pump improperly, leading to
congestive heart failure
During the first several days following a heart attack, the heart has a tendency to lose its normal rhythm and fall into a dysfunctional pattern of beating that does not properly circulate blood. Treatment aimed to prevent or treat this condition, called an
, is conducted in a cardiac intensive care unit.
Long-term treatment to reduce the risk of heart attacks generally involves aspirin to prevent blood clots, as well as treatments to slow, stop, or reverse atherosclerosis. The latter is accomplished through the use of medications that keep cholesterol and blood pressure within normal limits, as well as by increasing exercise and improving other aspects of lifestyle.
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