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).
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.