The heart requires its own constant supply of oxygen and nutrients, like any muscle in the body. Two large, branching coronary arteries deliver oxygenated blood to the heart muscle. If one of these arteries or branches becomes blocked suddenly, a portion of the heart is starved of oxygen, a condition called "cardiac ischemia."
If cardiac ischemia lasts too long, the starved heart tissue dies. This is a heart attack, otherwise known as a myocardial infarction -- literally, "death of heart muscle."
Most heart attacks occur during several hours -- so never wait to seek help if you think a heart attack is beginning. In some cases there are no symptoms at all, but most heart attacks produce some chest pain.
Other signs of a heart attack include shortness of breath, dizziness, faintness, or nausea. The pain of a severe heart attack has been likened to a giant fist enclosing and squeezing the heart. If the attack is mild, it may be mistaken for heartburn. The pain may be constant or intermittent. Also, women are less likely to experience the classic symptoms of chest pain than men are.
Angina: Early Warning Sign of a Heart Attack
Many heart attack victims are warned of trouble by episodes of angina, which is chest pain that, like a heart attack, is provoked by ischemia. The difference is mainly one of degree: With angina, blood flow is restored, pain recedes within minutes, and the heart is not permanently damaged. With a heart attack, blood flow is critically reduced or fully blocked, pain lasts longer, and heart muscle dies without prompt treatment.
About 25% of all heart attacks occur without any previous warning signs. They are sometimes associated with a phenomenon known as "silent ischemia" -- sporadic interruptions of blood flow to the heart that, for unknown reasons, are pain-free, although they may damage the heart tissue. The condition can be detected by ECG (electrocardiogram) testing. People with diabetes often have silent ischemia.
A quarter of all heart attack victims die before reaching a hospital; others suffer life-threatening complications while in the hospital. Serious complications include stroke, persistent heart arrhythmias (irregular heart beats), heart failure, formation of blood clots in the legs or heart, and aneurysm, or bulging, in a weakened heart chamber. But those who survive the initial heart attack and are free from major problems a few hours later stand a better chance of full recovery.