Pre-Algebra on Khan Academy: No way, this isn't your run of the mill arithmetic. This is Pre-algebra. You're about to play with the professionals. Think of pre-algebra as a runway.
Heart attack - Causes. Heart attacks are caused by the blood supply to the heart being suddenly interrupted. Without this supply, heart muscles may be damaged and begin to die. Without treatment, the heart muscles will experience irreversible damage.
Heart attacks are caused by coronary artery disease, the medical term for narrowing of the arteries that supply blood to the heart muscle. The narrowing of the arteries is caused by formation of a plaque on the lining of the artery (called atherosclerosis).