Most heart attacks are caused by a blood clot that blocks one of the coronary arteries. The coronary arteries bring blood and oxygen to the heart. If the blood flow is blocked, the heart is starved of oxygen and heart cells die.
The medical term for this is myocardial infarction.
A substance called plaque can build up in the walls of your coronary arteries. This plaque is made up of cholesterol and other cells.
A heart attack may occur when:
A tear in the plaque occurs. This triggers blood platelets and other substances to form a blood a clot at the site that blocks most or all of the oxygen-carrying blood from flowing to a part of the heart muscle. This is the most common cause of heart attack.
A slow buildup of plaque may narrow one of the coronary arteries so that it is almost blocked.
In either case, there is not enough blood flow to the heart muscle and heart muscle dies.
The cause of heart attack is not always known.
Heart attack may occur:
When you are resting or asleep
After a sudden increase in physical activity
When you are active outside in cold weather
After sudden, severe emotional or physical stress, including an illness
The pain most often lasts longer than 20 minutes. Rest and a medicine to relax the blood vessels (called nitroglycerin) may not completely relieve the pain of a heart attack. Symptoms may also go away and come back.
Some people (the elderly, people with diabetes, and women) may have little or no chest pain. Or, they may have unusual symptoms such as shortness of breath, fatigue, and weakness. A "silent heart attack" is a heart attack with no symptoms.
Exams and Tests
A health care provider will perform a physical exam and listen to your chest using a stethoscope.
The provider may hear abnormal sounds in your lungs (called crackles), a heart murmur, or other abnormal sounds.
You may have a fast or uneven pulse.
Your blood pressure may be normal, high, or low.
You will have an electrocardiogram (ECG) to look for heart damage. Most of the time, certain changes on the ECG indicate you are having a heart attack. Sometimes these changes are not present, even though other tests indicate you have had a heart attack. This can be called NSTEMI.
A blood test can show if you have heart tissue damage. This test can confirm that you are having a heart attack. You will likely have this test 3 times over the first 6 to 12 hours.
You will be hooked up to a heart monitor, so the health care team can see how regularly your heart is beating.
You will receive oxygen so that your heart doesn't have to work as hard.
An intravenous line (IV) will be placed into one of your veins. Medicines and fluids pass through this IV.
You may get nitroglycerin and morphine to help reduce chest pain.
You may receive aspirin, unless it would not be safe for you. In that case, you will be given another medicine that prevents blood clots.
Dangerous abnormal heartbeats (arrhythmias) may be treated with medicine or electric shocks.
Angioplasty is a procedure to open narrowed or blocked blood vessels that supply blood to the heart.
Angioplasty is often the first choice of treatment. It should be done within 90 minutes after you get to the hospital, and usually no later than 12 hours after a heart attack.
A stent is a small, metal mesh tube that opens up (expands) inside a coronary artery. A stent is usually placed after or during angioplasty. It helps prevent the artery from closing up again.
You may be given drugs to break up the clot. This is called thrombolytic therapy. It is best if these drugs are given soon after the onset of symptoms, usually no later than 12 hours after it and ideally within 30 minutes of arriving to the hospital.
Some people may also have heart bypass surgery to open narrowed or blocked blood vessels that supply blood to the heart. This procedure is also called coronary artery bypass grafting and/or open heart surgery.
After a heart attack, you have a higher chance of having another heart attack.
How well you do after a heart attack depends on several factors such as:
The amount of damage to your heart muscle and heart valves
Where that damage is located
Your medical care after the heart attack
If your heart can no longer pump blood out to your body as well as it used to, you may develop heart failure. Abnormal heart rhythms can occur, and they can be life-threatening.
Most people can slowly go back to normal activities after a heart attack. This includes sexual activity. Talk to your health care provider about how much activity is good for you.
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Michael A. Chen, MD, PhD, Associate Professor of Medicine, Division of Cardiology, Harborview Medical Center, University of Washington Medical School, Seattle, WA. Also reviewed by David Zieve, MD, MHA, Isla Ogilvie, PhD, and the A.D.A.M. Editorial team.