A heart attack (also called myocardial infarction or MI) occurs when an area of heart muscle is completely deprived of blood, and the heart muscle cells die.
A heart attack may result when plaque inside the heart arteries breaks open or ruptures, forming a clot that significantly blocks blood flow through the artery.
A plaque is made up of cholesterol, white blood cells, calcium, and other components; it is surrounded by a fibrous cap. If a sudden surge in blood pressure causes the artery to constrict, the fibrous cap may tear or rupture. This signals the body to repair the injured artery lining, much as it might heal a cut on the skin, by forming a blood clot to seal the area. A blood clot that forms in an artery can completely block blood flow to the heart muscle and cause a heart attack.
The pain of a heart attack often occurs with other symptoms, including:
The pain of a heart attack usually will not go away with rest.
It is important to recognize the early stages of a heart attack and to seek emergency care. Medical treatment is needed to prevent death. Sometimes medicines can be given to reduce the damage to the heart muscle caused by a heart attack.
What causes a heart attack?
The underlying cause of unstable angina and heart attack is decreased blood flow to the heart. In most cases, this results from plaque buildup and rupture in the coronary arteries. Some plaques are unstable and are prone to rupture or tear. When this happens, a clot forms over the ruptured area and may block blood flow in the artery. When the heart muscle does not receive enough oxygen-rich blood, the muscle is damaged, and a heart attack occurs. If the blood flow is partially blocked or blocked for a short period of time and then resolves, it may cause unstable angina.
Plaque is made up of excess cholesterol, calcium, and other substances in your blood that over time build up on the inside walls of your coronary arteries. When plaque builds up on the inside of your arteries anywhere in your body, it is called atherosclerosis. When plaque builds up in the arteries of the heart, it is called coronary artery disease. Atherosclerosis is usually the result of years of high levels of "bad" (LDL) cholesterol, high blood pressure, smoking, and other risk factors. See an illustration of an artery blocked by atherosclerosis.
Sudden intense exercise, sudden strong emotion, or illegal drug use, for example, can trigger a heart attack by causing a rapid rise in blood pressure, a surge in adrenaline and other hormones, and other physical reactions. However, in most cases, there is no clear reason why heart attacks occur when they do.