Also known as a myocardial infarction, a heart attack occurs when one (or more) of the coronary arteries that supply blood to the heart become blocked, or blood flow is severely reduced.
Blockages are caused by a buildup of fatty, cholesterol-containing deposits called plaques in the artery walls, which causes the inside of the arteries to narrow over time. This process is called Atherosclerosis and is known to be the major cause of Coronary Heart Disease. Also, a reduction in blood flow can be caused by a blood clot. Clots can form when a plaque ruptures, and pieces of the plaque break away from the artery walls.