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.
As time goes on, less and less oxygen makes it to the heart, which can cause a heart attack. Coronary artery disease can lead to heart failure and arrhythmias (irregular heart beats). While some people are genetically predisposed to heart disease, it often develops due to poor lifestyle habits.