Hart attack

A heart attack occurs when blood flow to a part of your heart is blocked for a long enough time that part of the heart muscle is damaged or dies. Your doctor calls this a myocardial infarction.

Causes, incidence, and risk factors

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.
A hard 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 can occur as a result of plaque buildup.

• The plaque can develop cracks or tears. Blood platelets stick to these tears and form a blood clot. A heart attack can occur if this blood clot completely blocks oxygen-rich blood from flowing to the heart. This is the most common cause of heart attacks.
• The slow buildup of plaque may almost block one of your coronary arteries. A heart attack may occur if not enough oxygen-rich blood can flow through this blockage. This is more likely to happen when your body is stressed (for example, by a serious illness).

The cause of heart attacks is not always known. Heart attacks 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

Cardiogenic shock is a state in which the heart has been damaged so much that it cannot supply enough blood to the organs of the body. This condition is a medical emergency.