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).
Heart attacks are caused by a build-up of fatty deposits in the arteries. These deposits are largely made up of LDL, or bad cholesterol, and they cause the arteries to become narrowed or blocked, cutting off the blood supply. The body's immune system tries to remove these fatty deposits, but goes into overdrive.