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.
A heart attack can be caused by many possible factors. Your heart muscle requires a steady supply of blood and oxygen. A heart attack occurs when that supply is interrupted or blocked. The release of a blood clot from hardened coronary arteries is often the culprit. Many illnesses, as well as drugs, especially cocaine and contraceptive pill usage, can cause a heart attack.