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).
Most heart attacks are likely caused by an imbalance in your central nervous system (CNS) and your autonomic (or unconscious) nervous system (ANS), which controls the function of our internal organs By Thomas S. Cowan, MD