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.
That is the mechanism responsible for that massive heart attack-induced death. Now, what causes the ventricular fibrillation? Indeed, it can be a heart attack, but there are other causes as well. Heart attack refers to a blockage of blood flow in one of the arteries nourishing the heart. You must remember the heart is a muscle and needs blood flow like your biceps or your triceps needs blood flow with nourishment, oxygen and so on.