A heart attack (myocardial infarction) occurs when blood flow to a part of your heart is blocked for a long enough time that some of the heart muscle is damaged or dies.
Most heart attacks are caused by blood clots that block one of the coronary arteries that supplies blood and oxygen to the heart. A hard substance called plaque, made up of cholesterol and other cells, can build up in the walls of your coronary arteries and restrict or block blood flow.
A heart attack is very serious and needs immediate medical attention. A person is at greatest risk of sudden death in the early hours of a heart attack.
Chest pain is the most common symptom. You may feel mild to severe pain in only one part of your body, or it may move from your chest to your arms, shoulder, neck, teeth, jaw, belly area, or back.