A heart attack occurs when the flow of blood to the heart is severely reduced or blocked. The blockage is usually due to a buildup of fat, cholesterol and other substances in the heart (coronary) arteries. The fatty, cholesterol-containing deposits are called plaques. The process of plaque buildup is called atherosclerosis.

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

Symptoms of a heart attack vary. Some people have mild symptoms. Others have severe symptoms. Some people have no symptoms.

Common heart attack symptoms include:

Women may have atypical symptoms such as brief or sharp pain felt in the neck, arm or back. Sometimes, the first symptom sign of a heart attack is sudden cardiac arrest.

Chest pain that may feel like pressure, tightness, pain, squeezing or aching

Pain or discomfort that spreads to the shoulder, arm, back, neck, jaw, teeth or sometimes the upper belly

Cold sweat

Fatigue

Heartburn or indigestion

Lightheadedness or sudden dizziness

Nausea

Shortness of breath

Some heart attacks strike suddenly. But many people have warning signs and symptoms hours, days or weeks in advance. Chest pain or pressure (angina) that keeps happening and doesn't go away with rest may be an early warning sign. Angina is caused by a temporary decrease in blood flow to the heart.

Coronary artery disease causes most heart attacks. In coronary artery disease, one or more of the heart (coronary) arteries are blocked. This is usually due to cholesterol-containing deposits called plaques. Plaques can narrow the arteries, reducing blood flow to the heart. If a plaque breaks open, it can cause a blood clot in the heart.

A heart attack may be caused by a complete or partial blockage of a heart (coronary) artery. One way to classify heart attacks is whether an electrocardiogram (ECG or EKG) shows some specific changes (ST elevation) that require emergency invasive treatment. Your health care provider may use ECG results to describe these types of heart attacks.

An acute complete blockage: of a medium or large heart artery usually means you've had an ST elevation myocardial infarction (STEMI).

A partial blockage: often means you've had a non-ST elevation myocardial infarction (NSTEMI). However, some people with NSTEMI have a total blockage.

Coronary artery spasm: This is a severe squeezing of a blood vessel that's not blocked. The artery generally has cholesterol plaques or there is early hardening of the vessel due to smoking or other risk factors.

Certain infections: COVID-19 and other viral infections may cause damage to the heart muscle.

Spontaneous coronary artery dissection (SCAD): This life-threatening condition is caused by a tear inside a heart artery.

Heart attack risk factors include:

Age: Men age 45 and older and women age 55 and 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. If you smoke, quit.

High blood pressure

High cholesterol or triglycerides

Obesity

Diabetes

Metabolic syndrome

Family history of heart attacks

Not enough exercise

Unhealthy diet

Stress

Illegal drug use

A history of preeclampsia

An autoimmune condition

Heart attack complications are often due to heart muscle damage. Potential complications of a heart attack include:

Irregular or atypical heart rhythms (arrhythmias): Heart attack damage can affect how electrical signals move through the heart, causing heartbeat changes. Some may be serious and can be deadly.

Cardiogenic shock: This rare condition occurs when the heart is suddenly and abruptly unable to pump blood.

Heart failure: A lot of damage to the heart muscle tissue can make the heart unable to pump blood. Heart failure can be temporary or long-lasting (chronic).

Inflammation of the saclike tissue surrounding the heart (pericarditis): Sometimes a heart attack triggers a faulty immune system response.

Cardiac arrest: Without warning, the heart stops. A sudden change in the heart's signaling causes sudden cardiac arrest. A heart attack increases the risk of this life-threatening condition. It can lead to death (sudden cardiac death) without immediate treatment.

A heart attack is often diagnosed in an emergency setting. If you've had or are having a heart attack, care providers will take immediate steps to treat your condition. If you're able to answer questions, you may be asked about your symptoms and medical history. Diagnosis of a heart attack includes checking blood pressure, pulse and temperature. Tests are done to see how the heart is beating and to check overall heart health. Tests to diagnose a heart attack include:

Electrocardiogram (ECG or EKG)

Blood tests

Chest X-ray

Echocardiogram

Coronary catheterization (angiogram)

Cardiac CT or MRI

Each minute after a heart attack, more heart tissue is damaged or dies. Urgent treatment is needed to fix blood flow and restore oxygen levels. Oxygen is given immediately. Specific heart attack treatment depends on whether there's a partial or complete blockage of blood flow.

Medications to treat a heart attack might include:

Aspirin: Aspirin reduces blood clotting. It helps keep blood moving through a narrowed artery.

Clot busters (thrombolytics or fibrinolytics): These drugs help break up any blood clots that are blocking blood flow to the heart. The earlier a thrombolytic drug is given after a heart attack, the less the heart is damaged and the greater the chance of survival.

Other blood-thinning medications

Nitroglycerin: This medication widens the blood vessels. It helps improve blood flow to the heart. Nitroglycerin is used to treat sudden chest pain (angina).

Morphine: This medicine is given to relieve chest pain that doesn't go away with nitroglycerin.

Beta blockers: These medications slow the heartbeat and decrease blood pressure. 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 lower unhealthy cholesterol levels. Too much bad (low-density lipoprotein, or LDL) cholesterol can clog arteries.

If you've had a heart attack, a surgery or procedure may be done to open a blocked artery. Surgeries and procedures to treat a heart attack include:

Coronary angioplasty and stenting: This procedure is done to open clogged heart arteries. If you've had a heart attack, this procedure is often done during a procedure to find blockages (cardiac catheterization).

Coronary artery bypass surgery (CABG): This is open-heart surgery. A surgeon takes a healthy blood vessel from another part of the body to create a new path for blood in the heart. The blood then goes around the blocked or narrowed coronary artery. CABG may be done as an emergency surgery at the time of a heart attack. Sometimes it's done a few days later, after the heart has recovered a bit.