Heart Attack (Myocardial Infarction)

A heart attack occurs when blood flow to a section of heart muscle becomes blocked. If the flow of blood isn’t restored quickly, the section of heart muscle becomes damaged from lack of oxygen and begins to die.

Heart attack is a leading killer of both men and women in the United States. But fortunately, today there are excellent treatments for heart attack that can save lives and prevent disabilities. Treatment is most effective when started within 1 hour of the beginning of symptoms.

Heart Damage
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Figure A is an overview of a heart and coronary artery showing damage (dead heart muscle) caused by a heart attack. Figure B is a cross-section of the coronary artery with plaque buildup and a blood clot.

Other names for a heart attack include myocardial infarction (MI), acute myocardial infarction (AMI) and acute coronary syndrome.

Get Help Quickly

If you think you or someone you’re with is having a heart attack, call 9–1–1 right away.

Acting fast at the first sign of heart attack symptoms can save your life and limit damage to your heart. Treatment is most effective when started within 1 hour of the beginning of symptoms.

The most common heart attack signs and symptoms are:

  • Chest discomfort or pain—uncomfortable pressure, squeezing, fullness, or pain in the center of the chest that can be mild or strong. This discomfort or pain lasts more than a few minutes or goes away and comes back.
  • Upper body discomfort in one or both arms, the back, neck, jaw, or stomach.
  • Shortness of breath may occur with or before chest discomfort.
  • Other signs include nausea (feeling sick to your stomach), vomiting, lightheadedness or fainting, or breaking out in a cold sweat.

If you think you or someone you know may be having a heart attack:

  • Call 9–1–1 within a few minutes—5 at the most—of the start of symptoms.
  • If your symptoms stop completely in less than 5 minutes, still call your doctor.
  • Only take an ambulance to the hospital. Going in a private car can delay treatment.
  • Take a nitroglycerin pill if your doctor has prescribed this type of medicine.

Cause of Heart Attacks

Heart attacks occur most often as a result of a condition called coronary artery disease (CAD). In CAD, a fatty material called plaque builds up over many years on the inside walls of the coronary arteries (the arteries that supply blood and oxygen to your heart). Eventually, an area of plaque can rupture, causing a blood clot to form on the surface of the plaque. If the clot becomes large enough, it can mostly or completely block the flow of oxygen-rich blood to the part of the heart muscle fed by the artery.

During a heart attack, if the blockage in the coronary artery isn’t treated quickly, the heart muscle will begin to die and be replaced by scar tissue. This heart damage may not be obvious, or it may cause severe or long-lasting problems.

Heart attack also can occur due to problems with the very small, microscopic blood vessels of the heart. This condition is called coronary microvascular disease. It’s believed to be more common in women than in men.

Another less common cause of heart attack is a severe spasm (tightening) of a coronary artery that cuts off blood flow through the artery. These spasms can occur in coronary arteries that don’t have CAD. It’s not always clear what causes a coronary artery spasm, but sometimes it can be related to:

  • Taking certain drugs, such as cocaine
  • Emotional stress or pain
  • Exposure to extreme cold
  • Cigarette smoking

Severe problems linked to heart attack can include heart failure and life-threatening heart arrhythmias (irregular heartbeats). Heart failure is a condition in which the heart can’t pump enough blood throughout the body. Ventricular fibrillation is a serious arrhythmia that can cause death if not treated quickly.

Who is at risk for a heart attack?

Major risk factors for heart attack that you can control include:

  • Smoking
  • High blood pressure
  • High blood cholesterol
  • Being overweight or obese
  • Physical inactivity
  • Diabetes (high blood sugar)

Risk factors that you cannot control include:

  • Age. Risk increases for men older than 45 years and for women older than 55 years (or after menopause).
  • Family history of early coronary artery disease. Your risk increases if your father or a brother was diagnosed with CAD before 55 years of age, or if your mother or a sister was diagnosed with CAD before 65 years of age.
  • Certain CAD risk factors tend to occur together. When they do, it’s called metabolic syndrome. In general, a person with metabolic syndrome is twice as likely to develop heart disease and five times as likely to develop diabetes as someone without metabolic syndrome.

What are the signs and symptoms of a heart attack?

Not all heart attacks begin with a sudden, crushing pain that is often shown on TV or in the movies. The warning signs and symptoms of a heart attack aren’t the same for everyone. Many heart attacks start slowly as mild pain or discomfort. Some people don’t have symptoms at all (this is called a silent heart attack).

Chest pain or discomfort

The most common symptom of heart attack is chest pain or discomfort. Most heart attacks involve discomfort in the center of the chest that lasts for more than a few minutes or goes away and comes back. The discomfort can feel like uncomfortable pressure, squeezing, fullness, or pain. It can be mild or severe. Heart attack pain can sometimes feel like indigestion or heartburn.

The symptoms of angina can be similar to the symptoms of a heart attack. Angina is pain in the chest that occurs in people with coronary artery disease, usually when they’re active. Angina pain usually lasts for only a few minutes and goes away with rest. Angina that doesn’t go away or that changes from its usual pattern (occurs more frequently or occurs at rest) can be a sign of the beginning of a heart attack and should be checked by a doctor right away.

Other common signs and symptoms

  • Upper body discomfort in one or both arms, the back, neck, jaw, or stomach
  • Shortness of breath may often occur with or before chest discomfort
  • Nausea (feeling sick to your stomach), vomiting, lightheadedness or fainting, or breaking out in a cold sweat

Not everyone having a heart attack experiences the typical symptoms. If you’ve already had a heart attack, your symptoms may not be the same for another one. The more signs and symptoms you have, the more likely it is that you’re having a heart attack.

How is a heart attack diagnosed?

The diagnosis of heart attack is based on your symptoms, your personal and family medical history, and the results of diagnostic tests.

Electrocardiogram (ECG, EKG)

An electrocardiogram detects and records the electrical activity of the heart. Certain changes in the appearance of the electrical waves on an EKG are strong evidence of a heart attack. An EKG also can show if you’re having arrhythmias (abnormal heartbeats), which a heart attack (and other conditions) can cause.

Blood tests

During a heart attack, heart muscle cells die and burst open, letting certain proteins out in the bloodstream. Blood tests can measure the amount of these proteins in the bloodstream. Higher than normal levels of these proteins in the bloodstream is evidence of a heart attack.

Commonly used blood tests include troponin tests, CK or CK–MB tests, and serum myoglobin tests. Blood tests are often repeated to check for changes over time.

Coronary angiography

Coronary angiography is a special X-ray exam of the heart and blood vessels. It's often done during a heart attack to help pinpoint blockages in the coronary arteries.

The doctor passes a catheter (a thin, flexible tube) through an artery in your arm or groin (upper thigh) and threads it to your heart. This procedure—called cardiac catheterization—is part of coronary angiography.

A dye that can be seen on X-ray is injected into the bloodstream through the tip of the catheter. The dye lets the doctor study the flow of blood through the heart and blood vessels.

If a blockage is found, another procedure, called angioplasty, may be used to restore blood flow through the artery. Sometimes during angioplasty, the doctor will place a stent (a small mesh tube) in the artery to help keep the artery open.

How is a heart attack treated?

Early treatment can prevent or limit damage to the heart muscle. Acting fast, at the first symptoms of heart attack, can save your life. Medical personnel can begin diagnosis and treatment even before you get to the hospital.

Certain treatments are usually started right away if a heart attack is suspected, even before the diagnosis is confirmed. These include:

  • Oxygen
  • Aspirin to prevent further blood clotting
  • Nitroglycerin, to reduce the workload on the heart and improve blood flow through the coronary arteries

Treatment for chest pain

Once the diagnosis of heart attack is confirmed or strongly suspected, treatments to try to restore blood flow to the heart are started as soon as possible. Treatments include medicines and medical procedures.

Thrombolytic medicines

These medicines (also called clot busters) are used to dissolve blood clots that are blocking the coronary arteries. To be most effective, these medicines must be given within 1 hour after the start of heart attack symptoms.

Beta blockers

These medicines decrease the workload on your heart. Beta blockers also are used to relieve chest pain or discomfort and to help prevent additional heart attacks. Beta blockers also are used to correct arrhythmias (irregular heartbeats).

Angiotensin-converting enzyme (ACE) inhibitors

These medicines lower blood pressure and reduce the strain on your heart. They also help slow down further weakening of the heart muscle.

Anticoagulants
 
These medicines thin the blood and prevent clots from forming in your arteries.

Antiplatelet medicines

These medicines (such as aspirin and clopidogrel) stop platelets (a type of blood cell) from clumping together and forming unwanted clots.

Other medicines

Medicines may also be given to relieve pain and anxiety, and to treat arrhythmias, which often occur during a heart attack.

Medical procedures

If medicines can’t stop a heart attack, medical procedures—surgical or nonsurgical—may be used. These procedures include the following.

Angioplasty

Coronary angioplasty can be used to open coronary arteries that are blocked by a blood clot. During angioplasty, a catheter (a thin, flexible tube) with a balloon on the end is threaded through a blood vessel to the blocked coronary artery. Then, the balloon is inflated to push the plaque against the wall of the artery. This widens the inside of the artery, restoring blood flow.

During angioplasty, a small mesh tube called a stent may be put in the artery to help keep it open. Some stents are coated with medicines that help prevent the artery from becoming blocked again.

Coronary artery bypass grafting (CABG)

Coronary artery bypass grafting is a surgery in which arteries or veins are taken from other areas of your body and sewn in place to bypass (that is, go around) blocked coronary arteries. This provides a new route for blood flow to the heart muscle.

Treatment after you leave the hospital

Most people spend several days in the hospital after a heart attack. When you leave the hospital, treatment doesn’t stop. At home, your treatment may include daily medicines and cardiac rehabilitation (rehab). Your doctor may recommend lifestyle changes, including quitting smoking, losing weight, changing your diet, and increasing your physical activity, to lower your chances of having another heart attack.

Cardiac rehabilitation

Your doctor may prescribe cardiac rehabilitation (cardiac rehab) to help you recover from a heart attack and to help prevent another heart attack. Almost everyone who has had a heart attack can benefit from rehab. The heart is a muscle, and the right exercise will strengthen it.

But cardiac rehab isn’t only about exercise. It also includes education, counseling, and learning about reducing your risk factors. Rehab will help you learn the best way to take care of yourself after having a heart attack and how to prevent having another one.

The cardiac rehab team may include doctors (your family doctor, a cardiologist, and/or a surgeon, nurses, exercise specialists, physical and occupational therapists, dietitians, and psychologists or other behavioral therapists.

How can a heart attack be prevented?

Lowering your risk factors for coronary artery disease (CAD) can help you prevent a heart attack. Even if you already have CAD, you can still take steps to lower your risk of heart attack.

Reducing the risk of heart attack usually means making healthy lifestyle choices. You also may need treatment for medical conditions that raise your risk.

Healthy lifestyle choices

Healthy lifestyle choices to help prevent heart attack include:

  • Following a low-fat diet rich in fruits and vegetables. Pay careful attention to the amounts and types of fat in your diet. Lower your salt intake. These changes can help lower high blood pressure and high blood cholesterol.
  • Losing weight if you're overweight or obese.
  • Quitting smoking.
  • Doing physical activity to improve heart fitness. Ask your doctor how much and what kinds of physical activity are safe for you.

Treat related conditions

In addition to making lifestyle changes, you can help prevent heart attacks by treating conditions you have that make a heart attack more likely:

  • High blood cholesterol. You may need medicine to lower your cholesterol if diet and exercise aren't enough.
  • High blood pressure. You may need medicine to keep your blood pressure under control.
  • Diabetes (high blood sugar). If you have diabetes, control your blood sugar levels through diet and physical activity (as your doctor recommends). If needed, take medicine as prescribed.

Have an emergency action plan

Make sure that you have an emergency action plan in case you or someone else in your family has a heart attack. This is especially important if you're at high risk or have already had a heart attack.

Talk with your doctor about the signs and symptoms of heart attack, when you should call 9–1–1, and steps you can take while waiting for medical help to arrive.

What should I know about life after a heart attack?

Many people survive heart attacks and live active and full lives. If you get help quickly, treatment can limit the damage to your heart muscle. Less heart damage improves your chances for a better quality of life after a heart attack.

Medical followup

After a heart attack, you will need treatment for coronary artery disease to prevent another heart attack. Your doctor may recommend:

  • Lifestyle changes, such as quitting smoking, following a healthy diet, increasing your physical activity, and losing weight, if needed
  • Medicines to control chest pain or discomfort, blood pressure, blood cholesterol, and your heart’s workload
  • Participation in a cardiac rehabilitation program

Returning to normal activities

After a heart attack, most people without chest pain or discomfort or other complications can safely return to most of their normal activities within a few weeks. Most can begin walking immediately. Sexual activity also can begin within a few weeks for most patients. Discuss with your doctor a safe schedule for returning to your normal activities.

If allowed by state law, driving can usually begin within a week for most patients who don’t have chest pain or discomfort or other complications. Each state has rules about driving a motor vehicle following a serious illness. People with complications shouldn’t drive until their symptoms have been stable for a few weeks.

Anxiety and depression after a heart attack

After a heart attack, many people worry about having another heart attack. Sometimes they feel depressed and have trouble adjusting to the new lifestyle that’s needed to limit further heart trouble. Your doctor may recommend medicine or professional counseling if you have depression or anxiety. Physical activity can improve mental well-being, but you should consult with your doctor before starting any fitness activities.

Risk of a repeat heart attack

Once you’ve had a heart attack, you’re at higher risk for another one. It’s important to know the difference between angina and a heart attack. The pain of angina usually occurs after exertion and goes away in a few minutes when you rest or take medicine as directed. During a heart attack, the pain is usually more severe than angina, and it doesn’t go away when you rest or take medicine. If you don’t know whether your chest pain is angina or a heart attack, call 9–1–1.

Remember, the symptoms of a second heart attack may not be the same as those of a first heart attack. Don’t take a chance if you’re in doubt. Always call 9–1–1 within 5 minutes if you or someone you’re with has symptoms of a heart attack.

Unfortunately, most heart attack victims wait 2 hours or more after their symptoms begin before they seek medical help. This delay can result in lasting heart damage or death.


Reference: The Heart, Blood, and Lung Institute.

This information is for general educational uses only. It may not apply to you and your personal medical needs. This information should not be used in place of a visit, call, consultation with or the advice of your physician or health care professional.

Communicate promptly with your physician or other health care professional with any health-related questions or concerns.

Be sure to follow specific instructions given to you by your physician or health care professional.

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