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 heart disease. Coronary heart disease (CHD) is the leading cause of heart attacks. CHD is a condition in which the coronary arteries (the major blood vessels that supply the heart with blood) get clogged up with deposits of cholesterol. These deposits are called plaques.
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.