A heart attack is an injury to the heart muscle caused by a loss of blood supply. It usually occurs when a blood clot blocks the flow of blood through a coronary artery — a blood vessel that feeds blood to a part of the heart muscle. Interrupted blood flow to your heart can damage or destroy a part of the heart muscle.

Years ago, a heart attack was often fatal. But today, thanks to better awareness of signs and symptoms and improved treatments, the vast majority of people who have a heart attack survive.

Your overall lifestyle — what you eat, how often you exercise and the way you deal with stress — plays a role in your recovery from a heart attack. In addition, a healthy lifestyle can help you prevent a first or subsequent heart attack by controlling risk factors that contribute to the narrowing of the coronary arteries that supply blood to your heart.

Heart attacks have many variable signs and symptoms. Not all people who have heart attacks experience the same ones or experience them to the same degree. Many heart attacks aren't as dramatic as the ones you've seen on TV or in the movies.

For example, heart attack symptoms in women, in older adults and in people with diabetes tend to be less pronounced. Some people have no symptoms at all. Still, the more signs and symptoms you have, the greater the likelihood that you may be having a heart attack.

Warning signs and symptoms of a heart attack include:

• Pressure, fullness or a squeezing pain in the center of your chest that lasts for more than a few minutes
• Pain extending beyond your chest to your shoulder, arm, back, or even to your teeth and jaw
• Increasing episodes of chest pain
• Prolonged pain in the upper abdomen
• Shortness of breath
• Sweating
• Impending sense of doom
• Lightheadedness
• Fainting
• Nausea and vomiting

A heart attack can occur anytime — at work or play, while you're resting, or while you're in motion. Some heart attacks strike suddenly, but many people who experience a heart attack have warning signs and symptoms hours, days or weeks in advance. The earliest predictor of an attack may be recurrent chest pain (angina) that's triggered by exertion and relieved by rest. Angina is caused by temporary, insufficient blood flow to the heart. The medical term for insufficient blood flow to the heart is "cardiac ischemia."

The medical term for a heart attack is "myocardial infarction." "Myo" refers to "muscle;" "cardio" refers to "heart;" "infarct" refers to "death of tissue from lack of oxygen." Like any muscle, the heart needs a steady supply of blood. Without blood, heart cells are injured, causing pain or pressure. If blood flow isn't restored, heart cells can die and scar tissue can form, replacing working heart tissue. The lack of blood flow to the heart also may trigger irregular heart rhythms that can be fatal.

Your heart beats approximately once a second. During a day, your heart pumps about 2,000 gallons of blood through your circulatory system. Your circulatory system includes arteries and veins. Veins bring oxygen-poor blood back to your heart. Arteries deliver oxygen-rich blood to all of the tissues of your body — including your heart muscle.

A heart attack occurs when one or more of the tiny arteries supplying your heart with oxygen-rich blood (coronary arteries) become blocked. These arteries are called coronary arteries and encircle your heart like a crown. Blockages are usually due to a blood clot that forms suddenly where a coronary artery has narrowed over the years from a buildup of cholesterol and other substances.

This buildup of cholesterol and other substances — collectively known as plaques — in arteries throughout the body is called atherosclerosis. When the coronary arteries narrow due to atherosclerosis, the condition is known as coronary artery disease. Coronary artery disease is the major underlying cause of heart attacks.

Rarely, a heart attack can occur when a blood clot from inside a diseased heart breaks loose and lodges in a healthy or narrowed coronary artery. Another uncommon cause of a heart attack is a spasm of a coronary artery that shuts down blood flow to part of the heart muscle. Drugs, such as cocaine, can cause such a life-threatening spasm.

A heart attack is not a static event. It's a dynamic process that typically evolves over several hours. With each passing minute, more heart tissue is deprived of blood and deteriorates or dies. However, if blood flow can be restored in time, damage to the heart can be limited or prevented.

Certain factors, called coronary risk factors, increase your risk of a heart attack. These factors contribute to the unwanted buildup of deposits (atherosclerosis) that narrows arteries throughout your body, including arteries to your heart. Coronary risk factors include:

• Tobacco smoke. Smoking and long-term exposure to secondhand smoke damage the interior walls of arteries — including arteries to your heart — allowing deposits of cholesterol to collect and hamper blood flow. Smoking also increases the risk of deadly blood clots forming and causing a heart attack.
• High blood pressure. Blood pressure is determined by the amount of blood your heart pumps and the amount of resistance to blood flow in your arteries. Over time, high blood pressure can damage arteries that feed your heart by accelerating atherosclerosis. High blood pressure can be an inherited problem. The risk of high blood pressure increases as you age, but the main culprits for most Americans are eating a diet too high in salt and being overweight.
• High blood cholesterol or triglyceride levels. Cholesterol is a major part of the deposits that can narrow arteries throughout your body, including those that supply your heart. A high level of the wrong kind of cholesterol in your blood increases your risk of a heart attack. Low-density lipoprotein (LDL) cholesterol (the "bad" cholesterol) is most likely to narrow arteries. A high LDL level is undesirable and is often a byproduct of a diet high in saturated fats and cholesterol. A high level of triglycerides, a type of blood fat related to your diet, also is undesirable. However, a high level of high-density lipoprotein (HDL) cholesterol (the "good" cholesterol), which helps the body clean up excess cholesterol, is desirable and lowers your risk of heart attack.
• Lack of physical activity. An inactive lifestyle contributes to high blood cholesterol levels and obesity. Conversely, people who get regular aerobic exercise have better cardiovascular fitness, which decreases their overall risk of heart attack. Exercise is also beneficial in lowering high blood pressure.
• Obesity. Obesity involves having a high proportion of body fat. Obesity raises the risk of heart disease because it's associated with high blood cholesterol levels, high blood pressure and diabetes.
• Diabetes. Diabetes is the inability of your body to produce or respond to insulin properly. Insulin, a hormone secreted by your pancreas, allows your body to use glucose, which is a form of sugar from foods. Diabetes can occur in childhood, but it appears more often in middle age and among overweight people. Diabetes greatly increases the risk of a heart attack by speeding up atherosclerosis and negatively affecting blood cholesterol levels.
• Stress. You may respond to stress in ways that can increase your risk of a heart attack. If you're under stress, you may overeat or smoke from nervous tension. Too much stress, as well as anger, can also raise your blood pressure.
• Alcohol. Consumed in moderation, alcohol helps raise HDL levels — the "good" cholesterol — and can have a protective effect against heart attack. On the other hand, excessive drinking can raise your blood pressure and triglyceride levels, increasing your risk of heart attack.
• Family history of heart attack. If your siblings, parents or grandparents have had early heart attacks, you may be at risk, too. Your family may have a genetic condition that raises unwanted blood cholesterol levels. High blood pressure also can run in families. In addition, families may contribute to coronary artery disease by practicing or promoting poor health habits, such as smoking or eating high-fat diets.
• Homocysteine, C-reactive protein and fibrinogen. People who have higher blood levels of homocysteine, C-reactive protein and fibrinogen appear to have an elevated risk of heart disease. These factors have only recently been identified as players in increasing cardiovascular disease risk. Research to pinpoint their exact role is ongoing. In the meantime, homocysteine levels can be reduced with folic acid supplements and a healthy diet. Fibrinogen and C-reactive protein levels may be reduced by modifying other risk factors for heart disease, such as quitting smoking, lowering cholesterol and exercising.

You can modify or eliminate many of these risk factors to reduce your chances of having a first or second heart attack. However, you can't change some risk factors, such as heredity and gender. Men are generally at greater risk than are women of heart attacks. However, the risk for women increases sometime after menopause, usually after age 55. If your father had heart disease before 55 or your mother had heart trouble before 65, your risk of developing heart disease is greater.

During a heart attack, some people waste precious minutes because they don't recognize the important signs and symptoms — or they deny them. Some people also delay calling for help because they're afraid to risk the embarrassment of a false alarm.

However, one of the most important things you can do to increase your survival after a heart attack is to recognize what's happening and to take immediate action. Of the people who die of heart attacks, about half die within the first hour after the onset of signs and symptoms.

Don't "tough out" the symptoms of a heart attack for more than five minutes. Call 911 or other emergency medical services for help. If you don't have access to emergency medical services, have someone drive you to the nearest hospital, such as a neighbor or friend. Drive yourself only as a last resort, if there are absolutely no other options. Driving yourself puts you and others at risk if your condition suddenly worsens.

If it turns out you weren't having a heart attack, doctors may be able to pinpoint the cause of your signs and symptoms and treat them.