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.
Coronary artery disease is a major cause of heart attacks. Heart attacks can also be caused by blood clots that form as a result of the use of certain prescription drugs (Vioxx, Bextra, Celebrex and Zelnorm) that thicken the blood, making it stickier and more likely to clot.