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.
Both heart attack and heart failure are serious medical conditions that can cause death. Heart attack is caused by sudden total clogging of an artery that gives blood to the heart muscle. This kills part of the muscle of the heart, which weakens the heart. Heart failure occurs when the heart cannot circulate blood through the body.