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 coronary artery disease, the medical term for narrowing of the arteries that supply blood to the heart muscle. The narrowing of the arteries is caused by formation of a plaque on the lining of the artery (called atherosclerosis).