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.
Most heart attacks are likely caused by an imbalance in your central nervous system (CNS) and your autonomic (or unconscious) nervous system (ANS), which controls the function of our internal organs By Thomas S. Cowan, MD