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.
Coronary artery disease. The most common underlying cause of heart attack is atherosclerosis, a condition in which a fatty substance called plaque builds up on the inside walls of blood vessels. When this occurs in the coronary arteries, it's known as coronary artery disease (CAD).
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.