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.
1 A heart attack results when a blood clot completely obstructs a coronary artery supplying blood to the heart muscle and heart muscle dies.  The blood clot that causes the heart attack usually forms at the site of rupture of an atherosclerotic, cholesterol plaque on the inner wall of a coronary artery.