What is a heart attack?

A myocardial infarction (commonly called a heart attack) is an extremely dangerous condition caused by
a lack of blood flow to your heart muscle. The lack of blood flow can occur because of many different
factors but is usually related to a blockage in one or more of your heart’s arteries. Without blood flow,
the affected heart muscle will begin to die. If blood flow isn’t restored quickly, a heart attack can cause
permanent heart damage and death.

A heart attack is a life-threatening emergency. If you suspect you or someone you're with is having a
heart attack, do not hesitate to call 911 (or your local emergency services phone number). Time is
critical in treating a heart attack, and a delay of even a few minutes can result in permanent heart
damage or death.

How common are heart attacks?

New heart attacks happen to about 635,000 people in the U.S. each year. About 300,000 people a year
have a second heart attack. About one in seven deaths in the U.S. is due to coronary heart disease,
which includes heart attacks.

What happens during a heart attack?

When a heart attack happens, blood flow to a part of your heart stops or is far below normal, which
causes that part of your heart muscle to die. When a part of your heart can’t pump because it’s dying
from lack of blood flow, it can disrupt the pumping sequence for the entire heart. That reduces or even
stops blood flow to the rest of your body, which can be deadly if it isn’t corrected quickly.

SYMPTOMS AND CAUSES

What causes a heart attack?

The vast majority of heart attacks occur because of a blockage in one of the blood vessels that supply
your heart. This most often happens because of plaque, a sticky substance that can build up on the
insides of your arteries (similar to how pouring grease down your kitchen sink can clog your home
plumbing). That buildup is called atherosclerosis.

Sometimes, plaque deposits inside the coronary (heart) arteries can break open or rupture, and a blood
clot can get stuck where the rupture happened. If the clot blocks the artery, this can deprive the heart
muscle of blood and cause a heart attack.

Heart attacks are possible without a blockage, but this is rare and only accounts for about 5% of all heart
attacks. This kind of heart attack can occur for the following reasons:

 Spasm of the artery: Your blood vessels have a muscle lining that allows them to become wider
or narrower as needed. Those muscles can sometimes twitch or spasm, cutting off blood flow to
heart muscle.

 Rare medical conditions: An example of this would be any disease that causes unusual
narrowing of blood vessels.

 Trauma: This includes tears or ruptures in the coronary arteries.

 Electrolyte imbalances: Having too much or too little of key minerals like potassium in your
blood can cause a heart attack.

 Eating disorders: Over time, an eating disorder can cause damage to your heart and ultimately
result in a heart attack.

Who is most at risk for a heart attack?

Several key factors affect your risk of having a heart attack. Unfortunately, some of these risk factors
aren't things you can control.

 Age and sex.

 Family history of heart disease.

 History of preeclampsia, a condition that can develop during pregnancy.

 Lifestyle.

 If you have certain health conditions or diseases.

Age and sex

Your risk of heart attack increases as you get older, and your sex also influences when your risk of a
heart attack starts to increase:

 Men: The risk of heart attack increases greatly at age 45.

 Women: The risk of heart attack increases greatly at age 50 or after menopause.

Family history

If you have a parent or sibling with a history of heart disease or heart attack — especially at a younger
age — your risk is even greater. That risk increases with the following:

 Your father or a brother who was diagnosed with heart disease at age 55 or younger.

 Your mother or a sister who was diagnosed with heart disease at age 65 or younger.

Lifestyle

The lifestyle choices you make can also affect your risk of having a heart attack. The following lifestyle
factors increase your risk of heart attack:

 Lack of physical activity.

 A diet high in sodium, sugar and fat.

 Smoking or tobacco use (including smokeless or chewing tobacco and vaping).

 Drinking too much alcohol.

Other diseases and health conditions

The following health conditions can increase your risk of heart attack:

 Diabetes.

 Obesity.

 High blood pressure (hypertension).

 High cholesterol (hyperlipidemia).

 Eating disorders (especially in younger individuals).

What are the symptoms of a heart attack?

Heart attacks can have a number of symptoms, some of which are more common than others. The
symptoms you have are also influenced by your sex, as with men and women being more likely to have
different heart attack symptoms.

Common heart attack symptoms

Symptoms most often described by people having a heart attack:

 Chest pain (angina). This symptom can be mild and feel like discomfort or heaviness, or it can be
severe and feel like crushing pain. It may start in your chest and spread (or radiate) to other
areas like your left arm (or both arms), shoulder, neck, jaw, back or down toward your waist.

 Shortness of breath or trouble breathing.

 Nausea or stomach discomfort. Heart attacks can often be mistaken for indigestion.

 Heart palpitations.

 Anxiety or a feeling of “impending doom.”

 Sweating.

 Feeling lightheaded, dizzy or passing out.

Heart attack symptoms in women

Medical research in recent years has shown that women may have the above symptoms, but also have a
higher chance of experiencing symptoms different from those listed above.

Women are less likely to describe the following:

 Chest pain, especially in the center of the chest.

 Discomfort that feels like indigestion.

Women are more likely to describe the following:

 Pain in the back, shoulders, neck, arms or abdomen.

 Nausea and vomiting.

Is acute coronary syndrome the same as a heart attack?

Acute coronary syndrome is a life-threatening condition that requires emergency medical care and can
result in a heart attack. Acute coronary syndrome is a name given to three types of coronary artery
disease associated with a sudden rupture of plaque inside the coronary artery:

 Unstable angina.

 ST-segment elevation myocardial infarction or heart attack (STEMI).*

 Non-ST segment elevation myocardial infarction or heart attack (NSTEMI).*

The location of the blockage, the length of time that blood flow is blocked and the amount of damage
that occurs determine the type of acute coronary syndrome.

*See the Electrocardiogram description in the Diagnosis & Tests section for an explanation of STEMI and
non-STEMI heart attacks.

DIAGNOSIS AND TESTS

How are heart attacks diagnosed?

Heart attacks are usually diagnosed in an emergency room setting. A healthcare provider will diagnose a
heart attack using the following:

 History and symptoms: The provider will ask you about the symptoms you experienced. If
someone was with you, the provider might also ask them to describe what happened.

 Lab testing: Heart attacks cause a specific chemical marker to show up in your blood.

 Heart-specific diagnostic tests: This includes tests that detect and record the electrical activity
in your heart.

 Imaging tests: These tests give providers a way to “see” inside your heart. Many of these tests
can also show the location of a blood flow blockage, which can guide treatment.

What tests will be done to diagnose this condition?

Anyone with heart attack symptoms should undergo a physical examination, including checking pulse,
blood oxygen levels, blood pressure, and listening to heart and lung sounds.

Other tests used to diagnose heart attack include:

 Electrocardiogram (abbreviated as EKG or ECG): This is one of the first tests done when
someone comes to an ER with heart attack symptoms. This test uses sensors called electrodes
that attach to the skin of your chest. The electrodes pick up electrical activity in the heart and
show it as a wave on a display or printout. By looking at the wave, providers can see the
 strength and timing of the electrical signal as it travels through your heart. When the signal
doesn’t travel like it should, the shape of the wave changes, which can indicate a heart attack or
similar problems. EKG for a heart attack is usually continuous to monitor for changes in heart
activity.

STEMI and non-STEMI heart attacks

The wave of your heart's electrical signal is divided into sections using letters of the alphabet starting at
P and ending at U. One particular section of the wave, the ST segment, shows activity in the heart's
lower two chambers. Those chambers are the left ventricle and right ventricle.

Normally, the ST segment is very flat, but a heart attack that affects the ventricles will often cause the ST
segment to be much taller than normal. Healthcare professionals call this kind of heart attack an ST-
Elevation Myocardial Infarction, or STEMI. Heart attacks, in general, are broadly split into STEMI and
non-STEMI categories, with STEMI heart attacks typically being more severe.

 Blood tests. During a heart attack, the damage to heart muscle cells almost always causes a
chemical marker to appear in your bloodstream. Blood tests that look for that marker are
among the most reliable methods to diagnose a heart attack.

Certain kinds of tests can provide pictures or computer-generated images of the heart. These include:

 Echocardiogram: This test uses ultrasound (high-frequency sound waves), similar to how bats
use ultrasound like a sonar to see obstacles. The ultrasonic waves will travel through and
bounce off different parts of your heart at different speeds. An echocardiogram can use that
information to generate a picture of the inside and outside of your heart.

 Angiogram: This test involves taking an X-ray after injecting a dye-like substance easily seen on
an X-ray into your blood. This allows doctors to see areas with little or no blood flow.

 Heart computed tomography (CT) scan: This imaging test uses X-rays and computer processing
to create a highly detailed scan of your heart.

 Heart MRI: This test uses a powerful magnetic field and computer processing to create an image
of your heart.

 Nuclear heart scans: Similar to angiography, these scans use a radioactive dye injected into your
blood. What sets them apart from an angiogram is that they use computer-enhanced methods
like computed tomography (CT) or positron emission tomography (PET) scans.