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 is injury to the heart muscle caused by a loss of blood supply. While heart attacks can be caused by an unhealthy life style, lack of exercise, poor diet, and stress, recently, heart attacks have been linked to a number of defective drugs, including Vioxx, Bextra, Celebrex and Zelnorm.