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 AED History. 2  Heart attack (cardiac arrest) became a leading cause of death after the turn of the century. Humans have always suffered from cardiac problems, but they usually died from causes such as infectious disease, long before reaching an age where heart problems threatened their life.