A heart attack occurs when the flow of blood to the heart is blocked. The blockage is most often a buildup of fat, cholesterol and other substances, which form a plaque in the arteries that feed the heart (coronary arteries).

Sometimes, a plaque can rupture and form a clot that blocks blood flow. The interrupted blood flow can damage or destroy part of the heart muscle.

A heart attack, also called a myocardial infarction, can be fatal, but treatment has improved dramatically over the years. It's crucial to call 911 or emergency medical help if you think you might be having a heart attack.

Common heart attack signs and symptoms include:

• Pressure, tightness, pain, or a squeezing or aching sensation in your chest or arms that may spread to your neck, jaw or back
• Nausea, indigestion, heartburn or abdominal pain
• Shortness of breath
• Cold sweat
• Fatigue
• Lightheadedness or sudden dizziness

Heart attack symptoms vary

Not all people who have heart attacks have the same symptoms or have the same severity of symptoms. Some people have mild pain; others have more severe pain. Some people have no symptoms. For others, the first sign may be sudden cardiac arrest. However, the more signs and symptoms you have, the greater the chance you're having a heart attack.

Some heart attacks strike suddenly, but many people have warning signs and symptoms hours, days or weeks in advance. The earliest warning might be recurrent chest pain or pressure (angina) that's triggered by activity and relieved by rest. Angina is caused by a temporary decrease in blood flow to the heart.

When to see a doctor

Act immediately. Some people wait too long because they don't recognize the important signs and symptoms. Take these steps:

• Call for emergency medical help. If you suspect you're having a heart attack, don't hesitate. Immediately call 911 or your local emergency number. If you don't have access to emergency medical services, have someone drive you to the nearest hospital.

  Drive yourself only if there are no other options. Because your condition can worsen, driving yourself puts you and others at risk.

• Take nitroglycerin, if prescribed to you by a doctor. Take it as instructed while awaiting emergency help.

• Take aspirin, if recommended. Taking aspirin during a heart attack could reduce heart damage by helping to keep your blood from clotting.

  Aspirin can interact with other medications, however, so don't take an aspirin unless your doctor or emergency medical personnel recommend it. Don't delay calling 911 to take an aspirin. Call for emergency help first.

What to do if you see someone who might be having a heart attack

If you see someone who's unconscious and you believe is having a heart attack, first call for emergency medical help. Then check if the person is breathing and has a pulse. If the person isn't breathing or you don't find a pulse, only then should you begin CPR.

Push hard and fast on the person's chest in a fairly rapid rhythm — about 100 to 120 compressions a minute.

If you haven't been trained in CPR, doctors recommend performing only chest compressions. If you have been trained in CPR, you can go on to opening the airway and rescue breathing.

A heart attack occurs when one or more of your coronary arteries becomes blocked. Over time, a buildup of fatty deposits, including cholesterol, form substances called plaques, which can narrow the arteries (atherosclerosis). This condition, called coronary artery disease, causes most heart attacks.

During a heart attack, a plaque can rupture and spill cholesterol and other substances into the bloodstream. A blood clot forms at the site of the rupture. If the clot is large, it can block blood flow through the coronary artery, starving the heart of oxygen and nutrients (ischemia).

You might have a complete or partial blockage of the coronary artery.

• A complete blockage means you've had an ST elevation myocardial infarction (STEMI).
• A partial blockage means you've had a non-ST elevation myocardial infarction (NSTEMI).

Diagnosis and treatment might be different depending on which type you've had.

Another cause of a heart attack is a spasm of a coronary artery that shuts down blood flow to part of the heart muscle. Using tobacco and illicit drugs, such as cocaine, can cause a life-threatening spasm.

Infection with COVID-19 also may damage your heart in ways that result in a heart attack.

Certain factors contribute to the unwanted buildup of fatty deposits (atherosclerosis) that narrows arteries throughout your body. You can improve or eliminate many of these risk factors to reduce your chances of having a first or another heart attack.

Heart attack risk factors include:

• Age. Men age 45 or older and women age 55 or older are more likely to have a heart attack than are younger men and women.
• Tobacco. This includes smoking and long-term exposure to secondhand smoke.
• High blood pressure. Over time, high blood pressure can damage arteries that lead to your heart. High blood pressure that occurs with other conditions, such as obesity, high cholesterol or diabetes, increases your risk even more.
• High blood cholesterol or triglyceride levels. A high level of low-density lipoprotein (LDL) cholesterol ("bad" cholesterol) is most likely to narrow arteries. A high level of triglycerides, a type of blood fat related to your diet, also increases your risk of a heart attack. However, a high level of high-density lipoprotein (HDL) cholesterol ("good" cholesterol) may lower your risk.
• Obesity. Obesity is linked with high blood cholesterol levels, high triglyceride levels, high blood pressure and diabetes. Losing just 10% of your body weight can lower this risk.
• Diabetes. Not producing enough of a hormone secreted by your pancreas (insulin) or not responding to insulin properly causes your body's blood sugar levels to rise, increasing your risk of a heart attack.
• Metabolic syndrome. This syndrome occurs when you have obesity, high blood pressure and high blood sugar. Having metabolic syndrome makes you twice as likely to develop heart disease than if you don't have it.
• Family history of heart attacks. If your siblings, parents or grandparents have had early heart attacks (by age 55 for males and by age 65 for females), you might be at increased risk.
• Lack of physical activity. Being inactive contributes to high blood cholesterol levels and obesity. People who exercise regularly have better heart health, including lower blood pressure.
• Stress. You might respond to stress in ways that can increase your risk of a heart attack.
• Illicit drug use. Using stimulant drugs, such as cocaine or amphetamines, can trigger a spasm of your coronary arteries that can cause a heart attack.
• A history of preeclampsia. This condition causes high blood pressure during pregnancy and increases the lifetime risk of heart disease.
• An autoimmune condition. Having a condition such as rheumatoid arthritis or lupus can increase your risk of a heart attack.

Complications are often related to the damage done to your heart during a heart attack, which can lead to:

• Abnormal heart rhythms (arrhythmias). Electrical "short circuits" can develop, resulting in abnormal heart rhythms, some of which can be serious, and may lead to death.
• Heart failure. A heart attack might damage so much heart tissue that the remaining heart muscle can't pump enough blood out of your heart. Heart failure can be temporary, or it can be a chronic condition resulting from extensive and permanent damage to your heart.
• Sudden cardiac arrest. Without warning, your heart stops due to an electrical disturbance that causes an abnormal heart rhythm (arrhythmia). Heart attacks increase the risk of sudden cardiac arrest, which can cause death without immediate treatment.

It's never too late to take steps to prevent a heart attack — even if you've already had one. Here are ways to prevent a heart attack.

• Medications. Taking medications can reduce your risk of a subsequent heart attack and help your damaged heart function better. Continue to take what your doctor prescribes, and ask your doctor how often you need to be monitored.
• Lifestyle factors. You know the drill: Maintain a healthy weight with a heart-healthy diet, don't smoke, exercise regularly, manage stress and control conditions that can lead to a heart attack, such as high blood pressure, high cholesterol and diabetes.

Ideally, your doctor should screen you during regular physical exams for risk factors that can lead to a heart attack.

If you're in an emergency setting for symptoms of a heart attack, you'll be asked about your symptoms and have your blood pressure, pulse and temperature checked. You'll be connected to a heart monitor and have tests to see if you're having a heart attack.

Tests to diagnose a heart attack include:

• Electrocardiogram (ECG). This first test done to diagnose a heart attack records electrical signals as they travel through your heart. Sticky patches (electrodes) are attached to your chest and limbs. Signals are recorded as waves displayed on a monitor or printed on paper. Because injured heart muscle doesn't conduct electrical impulses normally, the ECG may show that a heart attack has occurred or is in progress.
• Blood tests. Certain heart proteins slowly leak into your blood after heart damage from a heart attack. Emergency room doctors will take samples of your blood to check for these proteins, or enzymes.

Additional tests

If you've had or are having a heart attack, doctors will take immediate steps to treat your condition. You might also have these additional tests.

• Chest X-ray. An X-ray image of your chest allows your doctor to check the size of your heart and its blood vessels and to look for fluid in your lungs.
• Echocardiogram. Sound waves (ultrasound) create images of the moving heart. Your doctor can use this test to see how your heart's chambers and valves are pumping blood through your heart. An echocardiogram can help identify whether an area of your heart has been damaged.
• Coronary catheterization (angiogram). A liquid dye is injected into the arteries of your heart through a long, thin tube (catheter) that's fed through an artery, usually in your leg or groin, to the arteries in your heart. The dye makes the arteries visible on X-ray, revealing areas of blockage.
• Cardiac CT or MRI. These tests create images of your heart and chest. Cardiac CT scans use X-rays. Cardiac MRI uses a magnetic field and radio waves to create images of your heart. For both tests, you lie on a table that slides inside a long tubelike machine. Each can be used to diagnose heart problems, including the extent of damage from heart attacks.

Heart attack treatment at a hospital

Each minute after a heart attack, more heart tissue deteriorates or dies. Restoring blood flow quickly helps prevent heart damage.

Medications

Medications to treat a heart attack might include:

• Aspirin. The 911 operator might tell you to take aspirin, or emergency medical personnel might give you aspirin immediately. Aspirin reduces blood clotting, thus helping maintain blood flow through a narrowed artery.
• Thrombolytics. These drugs, also called clotbusters, help dissolve a blood clot that's blocking blood flow to your heart. The earlier you receive a thrombolytic drug after a heart attack, the greater the chance you'll survive and have less heart damage.
• Antiplatelet agents. Emergency room doctors may give you other drugs known as platelet aggregation inhibitors to help prevent new clots and keep existing clots from getting larger.
• Other blood-thinning medications. You'll likely be given other medications, such as heparin, to make your blood less "sticky" and less likely to form clots. Heparin is given by IV or by an injection under your skin.
• Pain relievers. You might be given a pain reliever, such as morphine.
• Nitroglycerin. This medication, used to treat chest pain (angina), can help improve blood flow to the heart by widening (dilating) the blood vessels.
• Beta blockers. These medications help relax your heart muscle, slow your heartbeat and decrease blood pressure, making your heart's job easier. Beta blockers can limit the amount of heart muscle damage and prevent future heart attacks.
• ACE inhibitors. These drugs lower blood pressure and reduce stress on the heart.
• Statins. These drugs help control your blood cholesterol.

Surgical and other procedures

In addition to medications, you might have one of these procedures to treat your heart attack:

• Coronary angioplasty and stenting. In this procedure, also known as percutaneous coronary intervention (PCI), doctors guide a long, thin tube (catheter) through an artery in your groin or wrist to a blocked artery in your heart. If you've had a heart attack, this procedure is often done immediately after a cardiac catheterization, a procedure used to find blockages.

  The catheter has a special balloon that, once in position, is briefly inflated to open a blocked coronary artery. A metal mesh stent almost always is inserted into the artery to keep it open long term, restoring blood flow to the heart. Usually, you get a stent coated with a slow-releasing medication to help keep your artery open.

• Coronary artery bypass surgery. In some cases, doctors perform emergency bypass surgery at the time of a heart attack. If possible, however, you might have bypass surgery after your heart has had time — about three to seven days — to recover from your heart attack.

  Bypass surgery involves sewing veins or arteries in place beyond a blocked or narrowed coronary artery, allowing blood flow to the heart to bypass the narrowed section.

  You'll likely remain in the hospital for several days after blood flow to your heart is restored and your condition is stable.

Cardiac rehabilitation

Most hospitals offer programs that might start while you're in the hospital and continue for weeks to a couple of months after you return home. Cardiac rehabilitation programs generally focus on four main areas — medications, lifestyle changes, emotional issues and a gradual return to your normal activities.

It's extremely important to participate in this program. People who attend cardiac rehab after a heart attack generally live longer and are less likely to have another heart attack or complications from the heart attack. If cardiac rehab is not recommended during your hospitalization, ask your doctor about it.

To improve your heart health, take the following steps:

• Avoid smoking. The most important thing you can do to improve your heart's health is to not smoke. Also, avoid being around secondhand smoke. If you need to quit, ask your doctor for help.
• Control your blood pressure and cholesterol levels. If one or both of these is high, your doctor can prescribe changes to your diet and medications. Ask your doctor how often you need to have your blood pressure and cholesterol levels monitored.
• Get regular medical checkups. Some of the major risk factors for a heart attack — high blood cholesterol, high blood pressure and diabetes — cause no symptoms early on. Your doctor can test for these conditions and can help you manage them, if necessary.
• Exercise. Regular exercise helps improve heart muscle function after a heart attack and helps prevent a heart attack. Get at least 150 minutes of moderate aerobic activity or 75 minutes of vigorous aerobic activity a week, or a combination of moderate and vigorous activity.
• Maintain a healthy weight. Excess weight strains your heart and can contribute to high cholesterol, high blood pressure and diabetes.
• Eat a heart-healthy diet. Saturated fat, trans fats and cholesterol in your diet can narrow arteries to your heart, and too much salt can raise blood pressure. Eat a heart-healthy diet that includes lean proteins, such as fish and beans, and fruits and vegetables and whole grains.
• Manage diabetes. Regular exercise, eating well and losing weight all help to keep blood sugar levels at more-desirable levels. Many people also need medication to manage their diabetes.
• Control stress. Reduce stress in your day-to-day activities. Rethink workaholic habits and find healthy ways to minimize or deal with stressful events in your life.
• Avoid or limit alcohol. If you choose to drink alcohol, do so in moderation. For healthy adults, that means up to one drink a day for women and up to two drinks a day for men.

Having a heart attack is scary, and you might wonder how it will affect your life and whether you'll have another one.

Fear, anger, guilt and depression are all common after a heart attack. Discussing them with your doctor, a family member or a friend might help. Or consider talking to a mental health provider or joining a support group.

It's important to mention signs or symptoms of depression to your doctor. Cardiac rehabilitation programs can be effective in preventing or treating depression after a heart attack.

Sex after a heart attack

Some people worry about having sex after a heart attack, but most people can safely return to sexual activity after recovery. When you can resume sexual activity will depend on your physical comfort, emotional readiness and previous sexual activity. Ask your doctor when it's safe to have sex.

Some heart medications can affect sexual function. If you're having problems with sexual dysfunction, talk to your doctor.

A heart attack usually is diagnosed in an emergency setting. However, if you're concerned about your risk of heart attack, see your doctor to check your risk factors and talk about prevention. If your risk is high, you might be referred to a heart specialist (cardiologist).

Here's some information to help you prepare for your appointment.

What you can do

When you make the appointment, ask if there's anything you need to do in advance, such as restrict your diet. You might need to fast before a cholesterol test, for example.

Make a list of:

• Your symptoms, including any that seem unrelated to coronary artery disease, and when they began
• Key personal information, including a family history of heart disease, stroke, high blood pressure or diabetes, and recent major stresses or recent life changes
• All medications, vitamins and other supplements you take, including doses
• Questions to ask your doctor

Take a friend or relative along, if possible, to help you remember the information you're given.

Some questions to ask your doctor about heart attack prevention include:

• What tests do I need to determine my current heart health?
• What foods should I eat or avoid?
• What's an appropriate level of physical activity?
• How often should I be screened for heart disease?
• I have other health conditions. How can I best manage these conditions together?
• Are there brochures or other printed material that I can have? What websites do you recommend?

Don't hesitate to ask other questions, as well.

What to expect from your doctor

Your doctor is likely to ask you questions, including:

• How severe are your symptoms?
• Are they constant or do they come and go?
• What, if anything, seems to improve your symptoms? If you have chest pain, does it improve with rest?
• What, if anything, worsens your symptoms? If you have chest pain, does strenuous activity make it worse?
• Have you been diagnosed with high blood pressure, diabetes or high cholesterol?

What you can do in the meantime

It's never too early to make healthy lifestyle changes, such as quitting smoking, eating healthy foods and becoming more active. These are main lines of defense against having a heart attack.