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.
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.